EPA-340/2-76-001
           EFFECT  OF AUTOMOTIVE
            PARTS ON VEHICLE AND
                 ENGINE EMISSIONS
    PHASE I - ORIGINAL  EQUIPMENT
      U.S. Environmental Protection Agency
        Mobile Source Enforcement Division
                Technical Support Branch
                 Washington, D.C. 20460

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                             EPA-340/2-76-001
     EFFECT  OF  AUTOMOTIVE
     PARTS OH VEHICLE AHD
        ENGINE EMISSIONS
PHASE  I  - ORIGINAL EQUIPMENT
                Prepared by

              Richard R.  Carlson
           Olson Laboratories, Inc.
           421 East Cerritos Avenue
           Anaheim, California  92805
            Contract No.  68-01-1957



             EPA Project  Officer:

              Roy L. Reichlen



                Prepared for

       U.S. ENVIRONMENTAL PROTECTION AGENCY
        Mobile Source Enforcement Division
           Technical Support Branch
            Washington, D.C. 20460


                December 1976

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                  REPORT AVAILABILITY
          Copies of this report are available from the Air
Pollution Technical Information Center, Environmental
Protection Agency, Research Triangle Park, North Carolina
27711, or may be obtained at a nominal cost from the National
Technical Information Service, 5285 Port Royal Road,
Springfield, Virginia 22261.
                      DISCLAIMER
          This report has been reviewed by the Office of
Enforcement, Mobile Source Enforcement Division, U.S.
Environmental Protection Agency, and approved for publica-
tion.  Approval does not signify that the contents neces-
sarily reflect the views and policies of the U.S. Environ-
mental Protection Agency, nor does mention of trade  names or
commercial products constitute endorsement or recommendation
for use or nonuse.
                          l i

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                       FOREWORD
          The Clean Air Act requires that new vehicles and
vehicle engines are to be warranteed by their manufacturer
to be designed, built, and equipped so as to conform with
applicable emission standards for their useful  life.  The
Environmental Protection Agency, Office of Enforcement,
Mobile Source Enforcement Division, is charged  with enforcing
compliance with applicable emission standards.   Classes of
vehicles or engines which are found to violate  applicable
standards during their useful life are subject  to recall  and
corrective repair at the manufacturer's cost, providing that
recommended maintenance and operating procedures had been
followed by the vehicle owner.
          However, surveillance test programs have shown
that a relatively high proportion of in-use vehicles fail to
comply with prescribed emission standards.  These failures
are generally related to malfunctions of specific components
of the engine or emission control systems which may be
defective, -tampered with, or improperly adjusted.  A key
step in correcting these emission failures is to identify
those components which are malfunctioning, how  these malfunc-
tions affect emissions, and how they can be detected.   With
this information, the EPA can then take the nece.ssary enforce-
ment action to ensure more effective compliance.
          The objective of this study, therefore, was to
assess the relative importance of engine and emission control
components in causing excessive emissions in the in-service
vehicle population.  The importance of each component was
measured by a criticality index based on factors representing
                         i 11

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t    Impact on emissions of a sing1e vehicle with
     a defective component
t    Probability of defect occurrence
t    Duration of defect occurrence
0    Relative usage of each component.

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                       ABSTRACT
          This final  report documents the methodology and
results of Phase I  of the Investigation of the Effect of
Automotive Parts on Vehicle and Engine Emissions.  This
study was performed for the Environmental Protection Agency,
Office of Mobile Source Enforcement, under Contract No.
68-01-1957.   The primary objective of this study was to
identify engine and emission control system components which
are critical in causing excessive emissions of one or more
regulated pollutants.  Phase I  of the study investigated the
emission-criticality  of original  equipment installed by the
engine or vehicle manufacturers.
          A computer  model  was  developed to calculate and
rank-order an index representing  the criticality of each
component type.  Separate rankings were developed for HC,
CO, NO  and smoke (heavy-duty diesel engines) emissions and
      ^
for pre-catalyst-equipped and catalyst-equipped vehicles.
The index for each  component type was calculated from the
product of four factors representing the emission increase
resulting from a component failure, the probability of
component failure,  the probability of component repair, and
the sales volume of the component.
          The values  of these factors were established based
on data obtained from a search  of technical literature and
engineering analysis  of system  and component design or
operating characteristics.   The study was performed without
emission or performance testing.   However, a series of tests
on 25 of the most emission-critical components was recommended
to develop or refine  data on emission increases and symptoms
of failure.

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           TABLE   OF   CONTENTS

                                                       Page

FOREWORD	iii

ABSTRACT 	 v

Section

1         INTRODUCTION AND SUMMARY 	 1-1
1.1       Summary of Major Findings	1-2
1.2       Statement of the Problem	1-5
1.3       Study Objectives 	 1-9
1.4       Study Scope	1-10
1.5       Study Plan	1-11

2         LITERATURE SEARCH	2-1
2.1       Component Usage	2-3
2.2       Effect of Component Failure on Emissions .   . 2-4
2.3       Probability and Duration of Component
           Failure	2-20
2.4       Sales Volume	'	2-26

3         EMISSIONS-RELATED COMPONENTS  	 3-1
3.1       Criteria and Assumptions	3-1
3.2       Carburetion System 	 3-4
3.2.1       Complete Carburetors 	 3-6
3.2.2       Carburetor Control  Devices  	 3-7
3.2.3       Carburetor Components	3-9
3.2.4       Fuel Filter	3-16
3.3       Ignition System	3-16
3.3.1       Points	3-18
3.3.2       Condenser/Capacitor	3-18
3.3.3       Distributor	3-19
3.3.4       Magnetic or Optical Triggers 	 3-23
3.3.5       Spark Plugs	3-23
3.3.6       Ignition Wires	3-24
3.3.7       Coils	3-25
3.3.8       Capacitive Discharge Systems 	 3-25
3.3.9       Ballast Resistor 	 3-26
3.3.10      Electronic Ignition Circuit	3-26
3.3.11      Glow Plug	3-26
3.3.12      Ignition Timing Adjustment  	 3-27
3.4       Air Induction System	3-28
3.4.1       Themostatically Controlled Air Inlet . .   . 3-28
3.4.2       Air Cleaner Element	3-30
3.4.3       Manifold	3-31
3.4.4       Turbochargers	3-31
3.4.5       Superchargers	3-32
3.5       Fuel  Injection System	3-32
3.5.1       Accumulator	 3-33
3.5.2       Fuel Pump (High Pressure)	3-33
                           VI 1

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   TABLE   OF   CONTENTS  (CONT'D)

Section                                                Page

3.5.3       Fuel  Pressure Sensors/Regulators 	 3-33
3.5.4       Throttle Linkage and Valve 	 3-34
3.5.5       Injection Valves 	 3-34
3.5.6       Air Sensors/Switches	3-35
3.5.7       Temperature Sensors/Switches 	 3-35
3.5.8       Fuel  Distribution Manifold	3-36
3.5.9       Injectors (Solenoid) 	 3-36
3.5.10      Triggering Switches	3-36
3.5.11      Electronic Fuel  Injection Control
             Circuits	3-37
3.5.12      Starting Valve 	 3-37
3.5.13      Idle  Adjustment  Screws 	 3-37
3.6       Engine  Systems	3-38
3.6.1       Exhaust Valve Components 	 3-38
3.6.2       Piston Rings	3-40
3.6.3       Pistons	3-41
3.6.4       Gaskets	3-41
3.6.5       Camshafts	3-42
3.7       Emission Control Systems 	 3-42
3.7.1       Positive Crankcase Ventilation (PVC)
             Systems	:   . 3-43
3.7.2       Evaporative Emission Control (EVAP)
             Systems	3-45
3.7.3       Air Injection (AI) System	3-47
3.7.4       Exhaust Gas Recirculation (EGR) Systems.   . 3-50
3.7.5       Transmission-Controlled Spark (TCS). .  .   . 3-54
3.7.6       Speed-Controlled Spark (SCS) System. .  .   . 3-57
3.7.7       Orifice Spark Advance Control (OSAC) .  .   . 3-58
3.7.8       Electronic Spark Control (ESC) System.  .   . 3-60
3.7.9       Catalytic Reactor	3-61
3.7.10      Miscellaneous Emission-Related Parts .  .   . 3-63
3.8       Emissions-Related  Part List	3-66

4         EMISSION-CRITICAL  COMPONENTS 	 4-1
4.1       Criticality Index  Model	4-1
4.1.1       Criticality Index	4-1
4.1.2       Emission Increase Factors	4-6
4.1.3       Probability of Failure Factors 	 4-7
4.1.4       Probability of Repair Factors	4-8
4.1.5       Sales Volume Factors 	 4-9
4.2       Assignment of Criticality Index Model
           Parameters	4-11
4.2.1       Effect of Defect on Emissions	4-11
4.2.2       Probability of Component Failure Factor.   . 4-41
4.2.3       Probability of Repair Factor 	 4-49
4.2.4       Component Sales  Volume 	 4-57
4.3       Ranking of Emission-Critical OEM Components. 4-63
                           VI 1 1

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 TABLE   OF   CONTENTS   (CONT'D)

Section                                                Page

5         SYMPTOMS OF FAILURE	5-1
5.1       Carburetion Components 	 5-7
5.2       Ignition System Components 	 5-8
5.3       Air Induction Components	5-10
5.4       Fuel  Injection Components	5-11
5.4       Mechanical  Components	5-11
5.6       Emission Control  Components	5-12
5.6.1       PCV System	5-13
5.6.2       EVAP System	5-13
5.6.3       Air Injection System	 5-14
5.6.4       EGR and Timing  Modulation Systems	5-14
5.6.5       Catalyst System	5-15
5.6.6       Thermal Vacuum  Valves	5-15
5.6.7       Electric Assist Choke	5-16
5.6.8       Heat Riser	5-16

6         RECOMMENDED TESTING	6-1
6.1       Selection of Components	6-1
6.1.1       Carburetion System Components	6-2
6.1.2       Ignition System Components 	 6-5
6.1.3       Air Induction System	6-9
6.1.4       Fuel Injection  System	6-9
6.1.5       Mechanical Components	6-9
6.1.6       Emission Control  Components	6-10
6.2       Test Protocol	6-14
6.2.1       Vehicle Selection	6-14
6.2.2       Preconditioning	6-15
6.2.3       Test Fuel	6-15
6.2.4       Inspection and  Maintenance. 	 6-15
6.2.5       Emission Tests	6-15

REFERENCES	R-l
                  APPENDICES

A         Critcality Index Ranking 	 A-l
B         Criticality Index Input Parameter Values .  . B-l
       LIST   OF   ILLUSTRATIONS

Figure                                                 Page

1-1       Study Approach	1-12
4-1       Criticality Model Flowchart	4-2
                          ix

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              LIST   OF   TABLES

Table                                                  Page

1-1       Criticality Index Ranking - Late Models. .  .  1-3
1-2       Criticality Index Ranking - All 1972 and
           Later Models	1-4
1-3       Symptoms of Component Failures	1-6
1-4       Components Recommended for Testing 	  1-8
2-1       Key Words Used for Literature Search ....  2-2
2-2       Engine Development Literature Not Applicable
           To Automotive Parts Study 	  2-5
2-3       Effect on Emissions of Various Components.  .  2-11
2-4       Effect of Idle Parameters on Hot FTP
           Emissions	2-14
2-5       Changes in 1975 FTP Emissions Caused By
           Specific Defects	2-15
2-6       Effect of Component Defects on 1975 FTP
           Emissions	2-16
2-7       Effect of  Component Defects on Hot FTP
           Emissions	2-18
2-8       Effect of Engine Variables on Steady State
           Emissions From Pre-1973 Vehicles	2-19
2-9       Incidence of Malfunctions	2-22
2-10      Estimated Durability of Automotive Parts .  .  2-23
2-11      Repairs Performed During Califoria Vehicle
           Emission Inspection Program 	  2-25
2-12      Incidence of Defects in Low Mileage Catalyst
           Vehicles	2-26
3-1       Emissions-Related Part List Original
           Equipment Parts 	  3-67
4-1       Criteria For Emission Increase Factors . .  .  4-6
4-2       Criteria For Probability of Failure Factors.  4-8
4-3       Criteria For Probability of Repair Factors  .  4-9
4-4       Scrappage As a Function of Vehicle Age . .  .  4-60
4-5       Typical Components With Design Life Less
           Than 50,000 Miles For Which 1 Or More
           Replacements Are Specified	4-6L
4-6       Criticality Index Ranking - Late Models. .  .  4-64
4-7       Criticality Index Ranking - All 1972 and
           Later Models	4-65
4-8       OEM Components Which Can Cause An Emission
           Failure	4-67
5-1       Possible Causes of Common Performance
           Problems	  5-3
5-2       Symptoms of Component Failure	5-5
6-1       Components Recommended For Testing 	  6-3

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                       Section 1

               INTRODUCTION AND SUMMARY
          This report documents the results of Phase I  of
the Investigation of the Effect of Automotive Parts on
Vehicle and Engine Emissions, EPA Contract 68-01-1957.
Phase I of this study included all "original  equipment"
installed by or for the vehicle or engine manufacturers to
ensure compliance with regulations issued under Title II of
the Clean Air Act.  For purposes of this study, original
equipment (OEM) components also included replacement com-
ponents available through the OEM dealer/service center
network.
          This section contains a summary of major findings,
a statement of the problem, and a description of the study
objectives, scope, and study plan.  Section 2 discusses the
literature search performed to obtain pertinent data and
information.  Section 3 describes emissions-related OEM
components and systems.  Section 4 discusses the emission-
critical  OEM components and the methodology used to rank
them in order of their criticality.  Section 5 discusses the
detectabi1ity and diagnosis of failures in the most critical
OEM components.  Section 6 concludes this report with a
recommended test protocol for 25 of the most critical OEM
components.
                         1-1

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1.1       SUMMARY OF MAJOR FINDINGS

          The major findings of Phase I of this study for
original  equipment (OEM) components were the following:

          •    Literature clearly defining the effect on FTP
               emissions from specific component defects
               exists for only a few common components or
               adj ustments.

          •    The ranking of emission-critical components
               is very sensitive to changes in the values of
               the input parameters representing the effect
               on emissions.  (See Tables 1-1 and 1-2 for
               criticality lists for post-1975 models and
               all post-1972 models, respectively.)

          •    Specific emission control system component
               usage within  certified engine families depends
               on such factors as transmission type, body
               style, and options such as air conditioning
               and heavy-duty cooling systems.

          •    The most emission-critical components for HC
               are typically ignition system components or
               components affecting air/fuel ratio.
               Catalysts are also critical to HC emissions
               from post-1975 model-year vehicles.

          t    The most emission-critical components for CO
               are typically carburetion components, although
               the air injection system, catalysts, and some
               ignition and mechanical components are also
               important.
                         1-2

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                                  Table 1-1.   CRITICALITY INDEX RANKING  -  LATE MODELS*
                                 (Automotive Parts Study - EPA Contract  No.  68-01-1957)
                                                                          SMOKE  (Diesel)
       TTT
        TU~
                                                  COMPOSITE
CO
Spark Plugs
Ignition Wires
CAT Active Media
Choke Mechanism
Power Valves
Heat Riser
EVAP Canister
Cap
Rotor
Idle Adjustment
TAC Vacuum Motor
TAC Vacuum Hoses
PCV Fresh Air Filter
PCV Valve
PCV Hoses
EVAP Hose
Valve Lifter/Spring
TAC Shroud
TAC Thermostat
Mag/Opt Triggers
EVAP Fresh Air
AI Pump/Belts
AI Hoses
Valve Seals
Exhaust Valves
Choke Mechanism
Power Valves
CAT Active Media
Metering Rods
Float and Valve
Vacuum Break Valve
Idle Adjustment
PCV Fresh/Air Filter
Air Cleaner Element
PCV Valve
AI Hoses
Spark Plugs
Vacuum Advance
AI Bypass Diverter
Valve Lifter/Spring
Ignition Wires
AI Pump/Belts
Valve Seals
Exhaust Valves
FI Starting Valve
Heat Riser
Mechanical Advance
Elec Assist Choke
AI Manifold
AI Check Valves
EGR Valves
EGR Thermo Valve
Thermo Vacuum Valve
EGR Vacuum Amplifier
Spark Delay Valve
EGR Hoses/Seals
Ignition Timing Adj
EGR Carb Spacer
EGR Backpress Sensor
EGR Speed/Trans Sen
OSAC Vacuum Orifice
EGR Solenoid Valve
EGR Time Delay
ESC Speed Switch
TCS Temp Switch
TCS Vacuum Solenoid
TCS Trans Switch
TCS Thermo Valve
ESC Elec Module
TCS Time Delay
SCS Thermo Valve
EGR Temp Switch
SCS Vacuum Solenoid
SCS Speed Switch
EFI Trigger Switch
                                                                        Valve  Lifter/Spring
                                                                        Valve  Seals
                                                                        Exhaust  Valves
                                                                        MFI  Valves
                                                                        Air  Cleaner  Element
                                                                        Valve  Cam Lobes
                                                                        Valve  Guides
                                                                        Piston Rings
                                                                        FI Throttle  Valve
                                                                        FI Idle  Adjustment
                                                                        Head Gaskets
                                                                        Camshafts
                                                                        FI Pressure  Sens/Reg
                                                                        Turbocharger
Spark Plugs
Ignition Wires
Choke Mechanism
Power Valve
Valve Lifter/Spring
EGR Valves
CAT Active Media
Valve Seals
Exhaust Valve
Metering Rods
EGR Thermo Vacuum
Float and Valve
Heat Riser
EVAP Canister
MFI Valves
Cap
Rotor
Thermo Vacuum Valve
Vacuum Break Valve
Idle Adjustment
TAC Vacuum Motor
TAC Vacuum Hoses
PCV Fresh Air Filter
Air Cleaner Element
EGR Vacuum Amplifier
       *Late models for HC, CO, and N0>, include 1975 and subsequent model  years.
        Late models for smoke include 1974 and subsequent model  years

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                     Table 1-2.  CRITICALITY INDEX RANKING  -  ALL  1972  AND  LATER MODELS
                          (Automotive Parts Study - EPA Contract  No. 68-01-1957)
       HC
                             IK)
                     SMOKE (Diesel)
                             COMPOSITE
Spark Plugs
Ignition Wires
Valve Lifter/Springs
Choke Mechanism
Power Valves
Valve Seals
Exhaust Valves
Rotor
Cap
CAT Active Media
EVAP Canister
Heat Riser
Points
Idle Adjustment
TAG Vacuum Motor
TAC Vacuum Hoses
Coil
Ballast Resistor
PCV Valve
PCV Fresh Air Filter
PCV Hoses
EVAP Hoses
Valve Cam Lobes
Valve Guides .
Piston Rings
Choke Mechanism
Power Valves
Valve Lifter/Springs
Float and Valve
Valve Seals
Exhaust Valves
Metering Rods
Air Cleaner Element
PCV Fresh Air Filter
Idle Adjustment
CAT Active Media
PCV Fresh Air Filter
Vacuum Break Valve
AI Hoses
Valve Cam Lobes
Valve Guides
Piston Rings
Vacuum Advance
AI Pump/Belts
Idle Stop Solenoid
Spark Plugs
AI Bypass/Diverter
Accelerator Pump
Ignition Wires
Metering Jets
EGR Valves
EGR Thermo Valve
Spark Delay Valve
EGR Vacuum Amplifier
Thermal Vacuum Valve
EGR Hoses/Seals
TCS Temp Switch
Ignition Timing Adj
TCS Trans Switch
TCS Vacuum Solenoid
EGR Solenoid Valve
TCS Time Delay
OSAC Vacuum Orifice
EGR Carb Spacer
EGR Backpress Sensor
TCS Thermal Valve
EGR Time Delay
EGR Temp Switch
EGR Speed/Trans Sw
OSAC Vacuum Bypass
ESC Speed Switch
ESC Elec Module
ESC Vacuum Valves
ESC Temp Switch
Dist Vac Decel Valve
MFI Valves
Valve Lifter/Springs
FI Throttle Valve
FI Idle Adjustment
Valve Seals
Exhaust Valves
FI Pres Sens/Reg
Air Cleaner Element
Valve Cam Lobes
Valve Guides
Piston Rings
Head Gaskets
Camshafts
Turbocharger
Spark Plugs
Ignition Wires
Choke Mechanism
Power Valves
MFI Valves
Valve Lifter/Springs
EGR Valve
Float and Valve
Exhaust Valves
Valve Seals
Metering Rods
EGR Thermal Valve
Air Cleaner Element
PCV Valve
Rotor
Cap
Idle Adjustment
Spark Delay Valve
CAT Active Media
PCV Fresh Air Filter
EVAP Canister
Heat Riser
FI Throttle Valve
FI Idle Adjustment
EGR Vacuum Amplifier

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          •     The  most  emission-critical  components  for NO
                                                           A
               are  typically  EGR system components and
               components  which  affect vacuum advance of
               timing.

          t     The  most  emission-critical  components  for
               smoke  from  diesel engines are typically
               mechanical  and fuel  injection components.

          t     Except  for  ignition  system components, most
               faulty  emission-critical components cannot be
               readily detected  by  the vehicle owner  or even
               by  an  automotive  mechanic unless  specific
               diagnostic  procedures are used which are not
               now routinely  performed during scheduled
               maintenance.   (See Table 1-3 for characteristic
               symptoms  of component failure.)

          A  series  of tests  were recommended on 25 components
to develop or refine  data  on  emissions increases and  symptoms
of failure.   These  components are summarized in Table 1-4.
1.2       STATEMENT OF THE PROBLEM

          The Clean Air Act (Section 207c) requires that all
new vehicles and vehicle engines are to be warranteed by the
vehicle or engine manufacturer to be designed, built, and
equipped so as to conform with applicable emission standards
for 50,000 miles providing that they are maintained, serviced,
and operated in accordance with written instructions provided
to the vehicle owner.  Classes (i.e., engine families of
vehicles or vehicle engines) which are found to violate the
applicable emissions standard during the 50,000-mile warranty
period are subject to recall and corrective repair at the
                         1-5

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                                        Table  1-3.   SYMPTOMS  OF  COMPONENT FAILURE
DEFECTIVE COMPONENTS
Carburetion System
Choke Components
Metering Rods
Float and Valve
Power Valve
Electric Assist Choke
Idle Adjustment
Vacuum Break Valve
Ignition System
Plugs/Wires
Cap/Rotor
Electronic Triggers
Timing Adjustment
Advance Mechanisms
Air Induction System
TAC Components
Ai r Cleaner
Vacuum Hose Leaks
Turbocharger
CRITICAL POLLUTANT
HC

X


X

X


X
X
X



X

X

CO

X
X
X
X
X
X
X

X



X


X


N0x












X






Smoke


















X
SYMPTOM OF FAILURE
Hard
Starting

X

X
X




X
X
X



X



Drive-
abi lity

X
X
X
X




X
X
X
X
X



X
X
Rough
Idle



X


X
X

X
X
X



X

X

Fuel
Economy

X
X
X
X

X


X


X
X


X

X
Back-
Firing



















I
CTi

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Table 1-3.   SYMPTOMS OF COMPONENT FAILURE (Continued)
DEFECTIVE COMPONENTS
•
Fuel Injection System
EFI Trigger Switch
EFI Starting Valves
Injection Valves
Pressure Reg/Sensors
Mechanical System
Valve Components
Rings
Gaskets
Emission Control System
Catalyst
PCV Components
EGR Components
EVAP Components
AI Components
Heat Riser
TCS/SCS Components
Spark Delay Valves
Thermal Vac Switches
CRITICAL POLLUTANT
HC






X



X
X

X
X
X



CO


X



X



X
X


X
X



NO
X

X










X



X
X
X
Smoke



X
X

X
X
X










SYMPTOM OF FAILURE
Hard
Starting

x •

X











X



Drive-
abi lity

X
X
X
X

X
X
X






X



Rough
Idle

X

X


X
X
X


X
X
X
X
X



Fuel
Economy

X
X
X
X

X
X
X










Back-
Firing

X
X











X





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                              Table 1-4.   COMPONENTS RECOMMENDED FOR TESTING
        COMPONENT
                DEFECT
        VARIABLE RANGE
Carburetion System
  1.  Choke
  2.  Float and Valve
  3.  Power Valve
  4.  Idle Adjustment
  5.  Metering Rod
  6.  Vacuum Break Valve

Ignition System
  1.  Spark Plugs
  2.  Wires
  3.  Cap
  4.  Rotor
  5.  Vacuum Advance
  6.  El Mag Trigger
  7.  Basic Timing

Air Induction System
  1.  Thermal Air Inlet

Mechanical System
  1.  Valve Adjustment
  2.  Exhaust Valve

Emission Control System
  1.  Heat Riser
  2.  Catalyst
  3.  Air Injection System
  4.  PCV Valve
  5.  Spark Delay Valve
  6.  EGR Valve
  7.  Backpressure Sensor
  8.  EGR Thermal Valve
  9.  Thermal Vac Valve
Improper Adjustment
Improper Float Level
Stuck Open or Ruptured Diaphragm
Improper Mixture
Improper Adjustment
Ruptured Diaphragm or Loose Vacuum Hose
Electrode Deterioration
Cable Deterioration
Terminal Corrosion or
Terminal Erosion
Ruptured Diaphragm or Loose Vacuum Hose
Deteriorated
Improper Adjustment
Ruptured Diaphragm or Loose Vacuum Hose
Improper Lash
Burned or Eroded
Stuck
Melted (Overheated)
Hose or Pump
Clogged
Stuck
Stuck
Clogged
Stuck
Stuck
Normal Opening - Delayed Opening
1/8" Low - 1/8" High
Operational - Failed
1/2 Turn In - 1/2 Turn Out
1/8" Low - 1/8" High
Operational - Failed
Wide Gap - Fouled
Open - Grounded
New - Old
New - Old
Operational - Failed
New - Old
SPEC  -10° - SPEC  +10°
Operational - Failed (Open)
Specification - 1/16" Excess
New - Old
Operational
Operational
Operational
Operational
Operational
Operational
Operational
Operational
Operational
Failed
Failed
Failed
Failed
Failed
Failed
Failed
Failed
Failed
(Open)
(Closed)
(Open)
(Closed)

(Closed)
(Open)

-------
manufacturer's cost in accordance with Section 207e of the
Clean Air Act.  As a result of the warranty provisions of
the Clean Air Act, manufacturers have issued specific mainte-
nance schedules covering those adjustments and component
replacements which the manufacturers have found to be impor-
tant in maintaining compliance with the emission standards
for 50,000 miles.
          However, surveillance test programs have shown
that a relatively high proportion of in-use vehicles fail to
comply with prescribed emission standards.  These failures
are generally related to malfunctions of specific components
of the engine or emission control systems which may be
defective, tampered with, or improperly adjusted.  A key
step in correcting these emission failures is to identify
those components which are malfunctioning, how these malfunc-
tions affect emissions, and how they can be detected.  With
this information, the EPA can then take the necessary action
to ensure compliance through recall programs and improved  .
maintenance procedures.
1.3       STUDY OBJECTIVES

          The objective of this study was to assess the
relative importance of engine and emission control components
in causing excessive emissions in the in-service vehicle
population.  The importance of each component was measured
by a criticality index based on factors representing:

          •    Impact on emissions of a single vehicle with
               a defective component
          t    Probability of defect occurrence
          •    Duration of defect occurrence
          t    Relative usage of each component.
                          1-9

-------
1.4       STUDY SCOPE

          This study was conducted in two phases with
separate reports issued for each phase.   Phase I consisted
of an assessment of the criticality of original factory-
installed (OEM) equipment.   Phase II consisted of an assess-
ment of the criticality of  after-market  equipment including
both high performance equipment and OEM  equivalent replacement
components.  Both Phases of this study were accomplished
without vehicle testing but were supported by a literature
search and engineering analysis.
          The emission-criticality of parts,  components  and
systems was determined separately for the following regulated
emissions:  hydrocarbons (HC), carbon monoxide (CO), oxides
of nitrogen (NO ) and smoke opacity.  The criticality rankings
               /\
were established for 1972 and subsequent model-year engines
and vehicles.  All  engines  subject to regulation were within
the nominal scope of the study; however, as a practical
matter, diesel engines and  heavy-duty gasoline engines were
not included in the criticality ranking  of HC, CO, and NO
because of their relatively low occurrence in the population.
For the same reason, manufacturers of light-duty vehicles
whose total sales in the U.S. were less  than  1 percent of
the applicable model-year vehicle production  were excluded.
The emission-criticality of components for smoke were based
on the most popular heavy-duty diesel engines.
          Because of the very large number of individual
components used by  engine and vehicle manufacturers, it  was
impossible to assign individual parameters to each component.
Rather, components  were grouped into classes  whose members
had similar function and configuration.   Each class or
category of components was  then assigned parameter values
which were applicable to all  individual  components within
each category.
                         1-10

-------
1.5       STUDY PLAN

          Figure 1-1 illustrates the sequence and interrela-
tionship of the tasks of each phase of this study.  The
initial effort was directed towards the literature search
and acquisition of pertinent data.   Simultaneously, the
criticality index model  was formulated, coded, and checked
out.  Subsequent Phase I activity included the following
tasks :

          t    Identify  emissions-related systems and
               components.
          t    Determine characteristic failure mode of each
               component.
          •    Determine effect on  emissions of each defect.
          •    Determine probability of defect occurring and
               probability of defect being corrected before
               end of component design life.
          •    Determine relat'ive usage (sales volume) of
               each OEM  component.
          •    Use the factors defined above to calculate a
               criticality index for each OEM component for
               each pollutant.
          •    Rank the  components  by criticality index.
          •    Describe  symptoms of failure and appropriate
               diagnostic techniques for the 25 most critical
               components for each  pollutant.
          •    Recommend a series of tests for 25 of the
               most critical OEM components to provide
               supportive data not available in the literature

          The above analyses, findings, conclusions and
recommendations formed the basis of this report on the
criticality of original  equipment.
                          1-11

-------
  TREPARE
  PLAN OF
  PERFORMANCE
ro
                     DEVELOP
                     CRITICALITY
                     INDEX (CI)
                     MODEL
VALIDATE
CI MODEL
                     IDENTIFY
                     EMISSIONS-
                     RELATED
                     PARTS
PERFORM
LITERATURE
SEARCH FOR
AFTER-MARKET
PARTS




DETERMINE
CRITICAL
OEM
PARTS

DETERMINE
CRITICAL
AFTER-MARKET
PARTS



DEFINE
SYMPTOMS OF
FAILURE FOR
OEM PARTS

DEFINE
CRITICAL
PARAMETERS
FOR AFTER-
MARKET PARTS




RECOMMEND
OEM
PARTS
TESTING

RECOMMEND
AFTER-MARKET
PARTS
TESTING





PREPARE
PHASE I
REPORT

PREPARE
PHASE II
REPORT

                                             Figure 1-1.  STUDY APPROACH

-------
          Phase  II  activity includes  the  following tasks
relative to after-market components,  parts, and systems:

          •    Redefine the values of the criticality index
               input parameters for after-market components.
          •    Execute the  criticality model  to select the
               most emission-critical after-market components
               for  each pol1utant.
          •    Determine the  critical parameters (specifi-
               cations or design characteristics)  of each of
               the  five most  critical after-market components
               for  each pol1utant.
          «    Recommend a  series of  tests for 25  of the
               most critical  after-market components.

          The analysis of after-market parts  is documented
in a separate report.
                           1-13

-------
                       Section 2

                   LITERATURE SEARCH
          An extensive search was conducted during the study
to identify all  potential  sources of information.  The
literature search was intended to obtain information for
each component which would support the following parameters
of the criticality index.

          •    Typical failure or defect modes.
          •    Probability and duration of failure.
          t    Consequence of the failure on emissions and
               performance.
          •    Sales volume  of vehicles, engines, and
               components.

          The literature search was performed by a pro-
fessional  search organization and included the following
data bases:

          •    National  Technical Information Service (NTIS)
          •    Chemical  Abstracts
          •    Engineering Index
          •    Pollution Abstracts

          The formal literature search was directed  chiefly
toward evaluating the effect of component defects on emis-
sions.  The literature search was conducted using the key
                         2-1

-------
words shown in Table 2-1.   Unfortunately, the search was
extremely broad, resulting in approximately 600 citations of
potentially applicable reports.   Review of the cited titles
and descriptors reduced to approximately 100 the number of
reports which appeared to  deserve detailed review.

   Table 2-1.  KEY WORDS USED FOR LITERATURE SEARCH

          Automobile(s)            Fuel Economy
          Automotive               Hydrocarbon(s)
          Carbon Monoxide           Ignition
          Carburetion              Internal Combustion
          Carburetor(s)            Maintainability
          Catalyst(s)              Mileage
          Component(s)             Mobile Source(s)
          Diesel                   Nitroic Oxide
          Durability               Oxide(s) of Nitrogen
          Electrical               Parts
          Emission(s)              Reactor
          Engine(s)                Smoke
          Exhaust                  Spark Ignition
          Expected Life            Vehicle

          In addition to the formalized literature  search,
extensive research was performed to define the type, quality,
and availability of data on performance and production of
engines, components, and systems.  This research involved
discussions with industry  and government representatives to
evaluate the applicability and accessibility of unpublished
data.  This evaluation indicated that, in general,  data of
the detail required by this study did not exist except for
a few specific components.
          The discussion of the literature search  is divided
into the following subject areas:

          t    Component usage.
          •    Effect of component failure on emissions.
                           2-2

-------
          •    Probability and duration of component failure.
          •    Sales volume.
2.1       COMPONENT USAGE

          In order to identify emissions-related components,
it was necessary to determine which components and systems
were used on 1972 and later vehicles.   The EPA has adopted
the concept of engine families for engines or vehicles which
have similar engine/ca^buretion/emissions control  system
configuration.  However, the engine family designations did
not necessarily reflect differences in body style, transmis-
sion type and accessory equipment even though these factors
can result in different component usage.   It was desirable
to obtain assembly parts lists by make/model/power train.
Unfortunately, this information was not available  from
either the vehicle manufacturers or the EPA.  Therefore, an
alternate source was sought out.
          The source eventually selected  to define component
usage was the Emission Control Service Manuals (Ref.  27)
published by Mitchell Manuals, Inc., San  Diego,  California.
The supplements for the model-years 1972  through 1975 were
obtained and used to define each distinctive engine family
according to the major emission control equipment  config-
uration.  The manuals distinguished families by  engine,
carburetor, transmission and, in some  cases, accessory
equipment.  Differences in system configurations for  California
and Federal vehicles were identified.   Vacuum and  electrical
diagrams were also presented permitting analysis of the
influence of defects in certain components on the  performance
of related components.
                           2-3

-------
2.2       EFFECT OF COMPONENT FAILURE ON EMISSIONS

          Twenty-seven papers were reviewed which described
the influence of engine and control  system design on emis-
sions.  These papers generally were  based on prototype tests
using nonstandard systems (CFR engines)  or operating condi-
tions (steady states).  Unfortunately, none of these papers
provided pertinent data on the probability or effect on
emissions of malfunctions in the engine  or system being
evaluated.  Several of these papers  also discussed systems
which have not been produced for sale.  Table 2-2 summarizes
the design and development papers which  were reviewed but
which did not provide useful data or information.
          Several papers (Ref. 19, 22, 37, 38, 40, 46, 48,
58, and 60) and books (Ref. 2 and 3) were used to help
define the operating principles and  design characteristics
of engine or emission control systems.  In general, these
documents did not provide data on the probability of failure
or the effect of defects on FTP emissions.  They did, however,
provide a basis for establishing probable modes of failure.
          Several papers (Ref. 35, 47, 72, 73, and 82)
reported durability test results on  production prototype
vehicles.  These papers, generally,  did  not describe specific
defects and their effect on emission levels.  The papers,
however, did give some insight into  the  probability of
failures and some typical system problems.  Presumably,
characteristic failures detected during  durability testing
were corrected prior to production.
          Weaver, et al (Ref. 35), reported data on a fleet
of 450 prototype catalyst vehicles.   In  general, they found
that maintenance performed in accordance with the manufac-
turer's recommended schedule enabled the vehicles to maintain
emission levels within 1975 statuatory standards for the
50,000-mile certification period.  Furthermore, the mainte-
nance actions did not affect HC emissions, decreased CO
                          2-4

-------
                Table 2-2.
              ENGINE DEVELOPMENT LITERATURE NOT APPLICABLE
                  TO AUTOMOTIVE PARTS STUDY
REFERENCE
   NO.
                         TITLE
  SOURCE '
    1



    4


    6


    8

    9

   10

   11
   18

   21


   23
Extension of the Lean Misfire Limit and Reduction
of Exhaust Emissions of an SI Engine by Modification
of the Ignition and Intake Systems.

Questor Reverter Emission Control  System Total  Vehicle
Concept.

Control of Refueling Emissions with an Activated
Carbon Canister on the Vehicle.

EFI Prechamber Torch Ignition of Lean Mixtures.

Emissions Study of a Single-Cylinder Diesel
  •
Factors .Affecting Dual Catalyst  System Performance

A Study of Ignition System Effects on Power, Emissions,
Lean Misfire Limit, and EGR Tolerance of a Single-  •
Cylinder  Engine - Multiple Spark Versus Conventional
Single Spark Ignition.

Efficient and Clean Diesel Combustion.

Trade-Offs between Engine Emission Control Variables,
Fuel Economy, and Octane.

Emissions Control of a Stationary  Two-Stroke
Spark-Gas Engine by Modification of Operating
Condi tions .
SAE 740105



SAE 730227


SAE 751181


SAE 750351

SAE 740123

SAE 740252

SAE 740188
SAE 750787

SAE SP-395
Inst. of Gas
Technol , Chi cago
6/5-7/72

-------
emissions and increased NO  emissions.   Unfortunately, the
                          y\
report did not relate specific maintenance actions or
defects to changes in emissions of individual  vehicles.
          The Weaver study also indicated that overtemperature
operation caused the greatest number of catalyst failures.
However, partially melted catalysts were found to have
residual activity although the 1975 HC  and CO  statuatory
standards were exceeded slightly.   Examination of the vehicles
with melted catalysts showed that  14 catalysts were damaged
by intermittent or total  ignition  loss  occurring within
10,000 miles.  The ignition failure was traced to defective
breaker points (five cases), primary coil wires (seven cases),
or ignition coil failure  (two cases).   In addition, two
catalysts were damaged by intermittent  ignition misfire
occurring at greater than 10,000 miles.  One each of these
failures was attributed to a loose primary coil wire and a
faulty coil.  There were  no cases  of catalyst  melting caused
by rich carburetion or other emis.sion  control  system defects.
Although all catalyst failures were caused by  ignition
failures, the incidence of ignition failure was small relative
to the fleet size (3.5 percent) which  is characteristic  of
the in-service noncatalyst vehicle population.
          Miles, et al (Ref. 47),  described a  durability
program of approximately  250 catalyst  vehicles.  Several
alternative design configurations  and  prototype components
were evaluated to establish performance data.   In general,
catalyst systems performed within  their design emission
standard for the 50,000-mile durability test.   Specific  data
on the effect of component failure were not presented,
although some vehicles did exceed  one  or more  of the standards
and some catalysts failed.  Difficulty  was reported with
prototype high energy ignition components which resulted in
misfire due partly to plug fouling.  Ignition  misfire was
believed to have caused the catalyst failures.  However,
converter failures occurred when at least two  cylinders  were
                          2-8

-------
misfiring.   More rapid deterioration of HC than CO emissions
generally occurred, with NOx emissions showing little
deterioration.
          A review of catalyst technology was prepared by
the National  Academy of Sciences (Ref. 15, 69, 72, 73, and
74).  Deactivation of catalysts was determined to be due to
thermal  cycling and excessive temperatures (Ref.  72).  The
catalytic media was sintered and agglomerated resulting in
increased void  (pore) size and decreased surface  area.
Severe thermal  stress lead to structural  deformation (melting
and col lapse) .
          The following specific defects leading  to catalyst
failure  were  identified from surveys of catalyst  development
and durability  testing (Ref. 72, 73, and 82):

          •    Severe dieseling after ignition shut-off.
          •    Running out of fuel  at high speed.
          •    Failure of coasting  protection (deceleration
               controls) .
          •    Misfire caused by ignition failure.
          t    Complete ignition failure at moderate to high
               speed.
          •    Stuck choke.
          •    Fuel which causes plug fouling.

          The frequency and  duration of failure and the
effectiveness of protective  devices (air injection dump)
determined  the  degree to which the  catalyst was degraded or
destroyed.   If  the catalyst  were to become essentially
deactivated and all other defects were corrected, the average
emission level  from catalyst-equipped vehicles was estimated
at 2.5 gm/mi  HC, 18.0 gm/mi  CO, and 5.0 gm/mi NO  .
          A summary MAS report (Ref. 70) presented a compila-
tion of  emission-critical  components which has been abstracted
                            2-9

-------
and is shown in Table 2-3.   These data  represented the
opinion of the NAS committee based on data available prior
to 1973.
          Matsumoto, et al  (Ref.  7), described an analysis
of catalyst reliability based on  empirical data.   The analysis
was performed to rank various component defects in order of
their criticality in causing catalyst failure.  Catalyst
failure was found to be critically-related to high temperature
Factors causing high catalyst temperature included hydrocarbon
concentration (misfire), exhaust  gas temperature  at the
inlet to the catalyst, and  flow rate of the exhaust gas.
Criticality of each defect  was determined by the  product of
a damage intensity factor and probabi1ity of repair factor.
The criticality ranking of  the components was as  follows:

          •    Two cylinders misfiring.
          t    One cylinder continuously misfiring.
          t    One cylinder intermittently misfiring.
          •    One cylinder occasionally misfiring.
          a    Choke valve  stuck.
          §    Fuel restriction (lean operation).
          •    Plugged air  bleed.
          •    Main jet fell out.
          •    Carburetor flooding.
          •    Primary jet  fell out.

          A study (Ref. 17) for the California Air Resources
Board (CARB) investigated the sensitivity of FTP  emissions
to various changes in test  conditions and engine  adjust-
ments.  Tests were performed on catalyst- and noncatalyst-
equipped vehicles.  Pertinent parameters investigated included
idle speed, basic timing, and idle mixture.  Unfortunately,
the emissions were tested using the hot start 1972 FTP.
Therefore, results using cold start FTP tests may be somewhat
different.  The results are summarized  in Table 2-4 in
                          2-10

-------
           Table 2-3.  EFFECT ON EMISSIONS OF VARIOUS COMPONENTS
                                                               1
NO. ITEM
Major Control Equipment
1* 3-way catalyst (HC, CO, NO)
A
2* Reduction catalyst (NOY)
A
3* Oxidation catalyst (HC, CO)
4* Exhaust manifold reactor
5 Exhaust gas recirculation valve
6 Air injection pump
These Can Cause A Catalyst Failure
7* Catalyst bypass
8* Catalyst thermocouple
9* Exhaust manifold reactor bypass
10* Exhaust air diverter valve
11* Oxygen sensor for 3-way catalyst
12* Electronic feedback control
13* Electronic fuel injection
14* Fast acting choke
15 Float valve
16 Power jet
17 Fuel pump
18 Spark plugs
19 Plug wires
20 Electronic ignition
21 Exhaust valve leaks
' — i 	 	 	
HC

H

H
M

M

H
H
M
M
M
M
M
H
M
L
L
H
H
L
H
CO

H

H
M

M

H
H
M
M
M
M
M
H
H
L
L


L

NOX

H
H


H
L




H
M
M
M
L.
L
L
L
M
M

M
MEAN TIME
TO FAILURE,
YEARS

2
2
2
10
5
5

5
2
5
8
2
8
8
5
5
10
5
2
3
10
10
SERVICE
INTERVAL,
YEARS

1
1
1
5
1
1

1
1
1
1
1
1
1
1
5
5
5
1
1
1
2
Components not in  production prior to 1973.
                                  2-11

-------
      Table 2-3.  EFFECT ON EMISSIONS OF VARIOUS COMPONENTS1 (Continued)
NO. ITEM
These Can Have A Major Effect on Emissions
22 Idle mixture screw
23 Idle speed screw
24 Fast idle speed screw
25 Heat riser valve
26 Air filter
27 PCV valve
28 PCV fittings and hoses
29 Distributor cap
30 Points
31 Coil wire
32 Air pump belt
33 Transmission controlled spark
switch
These Can Have Effect on Emissions
34 Coolant thermostat
35 Vacuum advance
36 Battery
37 Battery cables
38 Voltage regulator
39 Distributor rotor
40 Ignition condenser
41 Coil
42 Centrifugal advance
HC

H
L
L
M
L
M
L
M
H
H
H



M
L
L
L
M
M
H
M
CO

H
L
L
M
M
M
L















N0y
A

L









L
M

L
M
M





M
MEAN TIME
TO FAILURE,
YEARS

10
10
10
8
2
3
5
5
4
5
5
5

5
5
3
5
5
5
8
10
10
SERVICE
INTERVAL,
YEARS

1
1
1
1
1
1
1
1
1
1
1
1

5
2
2
2
5
1
1
1
1
1
 Table 12  from Reference  70.
                                   2-12

-------
      Table  2-3.   EFFECT ON  EMISSIONS OF VARIOUS COMPONENTS1 (Continued)
NO. ITEM
43 Intake manifold leaks
44 Carburetor metering rods
45 Carburetor internal vents
46 Carburetor float
47 Fuel filter
48 Carburetor accelerator pump
49* Quick heat manifold
50* PCV delay solenoid
51* Thermistor to sense coolant
52* Solenoid to activate EGR
53* Solenoid to activate evap. CS
54 Activated carbon ECS
55 Anti dieseling solenoid valve
56 CAP vacuum advance valve
57 Air injection check valve
58 Air cleaner thermostat
59 Distributor vacuum control valve
60 Gulp valve
61 Vacuum lines
HC
M
M
L
M
L
L
L
L
L

L
L
L
M
M
M
M


CO
L
M
M
M
L
L
M
L
L






M



NOX

L
L
L


:


M





L
M


MEAN TIME
TO FAILURE,
YEARS
5
8
10
10
2
5
10
5
5
5
5
5
3
8
5
5
5
5
3
SERVICE
INTERVAL,
YEARS
2
2
1
10
2
5
10
2
5
1
1
5
3
5
5
5
5
5
2
 Table 12 Reference  70.
Components not in production prior to 1973.
                                  2-13

-------
percent change relative to a hot start 1972 FTP baseline
test.
Table 2-4.   EFFECT OF IDLE PARAMETERS ON HOT FTP EMISSIONS
                       (REF.  17)

Timing +5°
Idle CO +1%
Idle Speed
-100 rpm
PRE-CATALYST
HC
+ 10%
-
+ 10%
CO
-
+ 15%
+ 10%
NOX
+ 15%
-
-
CATALYST-EQUIPPED
HC
-
+100%*
-
CO
-30%
+100%*
-25%
N0x
+ 20%
-

     *Baseline emissions approximately 1/3 of standard.

          The California Air Resources Board  (CARB)  performed
two studies (Ref.  92 and 93) of defects in catalyst-equipped
vehicles.   Table 2-5 summarizes these results in  terms  of
the increase (decrease)  on emissions  attributable to specific
component  defects.  The  results of these studies  show that
misfire due to faulty plugs or wires  was the  most critical
HC-related defect.  Other critical defects included  choke
malfunctions, air  injection failure,  lean misfire caused by
vacuum leaks and incorrect timing (10° retarded).  The  most
critical  CO-related defects were air  injection failure,
choke malfunction, retarded timing, and misfire.   The most
critical  NO -related defects were clearly disabled EGR
           rt
systems and advanced basic timing.
          Maugh (Ref. 100) presented  data, shown  in  Table 2-6,
on defect  testing  of the three different 1976 Federal certi-
fication  vehicles.  These data and other information discussed
in the paper led to the  following conclusions:

          t    Restricted air cleaner or timing variations
               of  ±10° did not significantly  affect  FTP
               emi ssions.
                           2-14

-------
     Table 2-5.  CHANGES  IN  1975 FTP  EMISSIONS CAUSED  BY  SPECIFIC  DEFECTS
                  (PERCENT INCREASE FROM BASELINE  EMISSIONS)
DEFECT
No EGR
Plugs/Wires
Vacuum Leak
Timing (advanced)
Timing (retarded)
Air Failure
Choke Stuck
Carburetor Mixture
Idle Stop Solenoid
Dirty Air Filter
INDUCED DEFECTS3
Number of
Vehicles
6
6
6
6
6
0
6
0
0
6
HC
33
833
83
17
133
-
433
-
-
50
CO
33
252
73
2
355
-
298
-
-
62
N0x
65
41
0
35
-12
-
-12
-
-
0
DIAGNOSED DEFECTS15
Number of
Vehicles
3
3
1
1
0
6
3
3
1
0
HC
0
731
150
-23
-
160
60
33
150
-
CO
12
14
-32
-47
-
365
170
26
33
-
N0x
65
35
11
64
-
-9
-15
4
15
-
 Defects  induced  in  low  mileage  catalyst  vehicles  (Ref. 92).

""Defects  diagnosed  in  low  mileage  catalyst  vehicles which  failed an idle HC
 screening  standard  of 200 ppm Hexane  (Ref. 93).
                                    2-15

-------
                               Table 2-6.   EFFECT OF COMPONENT DEFECTS ON 1975 FTP EMISSIONS

                                                  (EXHIBIT V OF REF. 101)

Baseline
Air Cleaner
Restricted 75%
Timing +10°
Timing -10°
EGR Line Off
Thermactor
Disconnected
Choke Restricted
50% Travel
Spark Plug
Wire Grounded
2.3L 4-CYLINDER
HC
0.51
0.47
0.60
0.49
0.43
0.68
0.50
10.20
CO
2.31
2.14
3.52
2.34
1.56
11.10
3.95
7.57
N0x
1.76
2.18
3.12
1.19
6.44
1.32
1.45
2.84
351 CID 8-CYLINDER
HC
0.62
0.60
0.63
0.55
0.44
2.23
0.57
4.11
CO
4.97
5.06
3.75
5.02
2.69
69.30
6.84
4.65
N0x
1.24
1.08
1.65
0.93
4.25
0.93
0.85
1.69
460 CID 8-CYLINDER
HC
0.51
0.40
0.51
0.32
0.33
2.46
17.80
2.61
CO
3.04
1.70
2.13
3.22
1.55
66.10
322.00
8.57
N0x
1.46
1.41
1.81
1.23
5.60
1.24
0.35
2.55
ro

i—•
en

-------
          t    Disconnected air injection caused significant
               increases in HC and CO emissions but reduced
               NO  emissions.
                 /\

          t    A stuck choke increased HC and CO emissions
               on large engines but not necessarily on small
               engines.  NO  emissions were reduced, signifi-
                           ^
               cantly on large engines.

          •    Total  misfire caused significantly higher HC
               emissions particularly on small  engines.   CO
               and NO  emissions also increased although not
                     A
               as much as HC emissions.

          Two EPA studies investigated tampering and malad-
justments of 1973-1975 model-year vehicles.  Timing maladjust-
ments of up to ±5° alone resulted in 10 percent to 20 percent
increases in FTP emissions of  HC and CO from 1975 model-year
vehicles.  Emissions  of NO  were increased 20 percent by a
 f\
5  advance in timing  and reduced 20 percent by  retarding
timing 5° (Ref. 98).   Several  1973-1974 model-year vehicles
were sent to commercial garages to have their fuel  economy
improved.  Although most adjustments did not improve fuel
economy, emissions of all three pollutants were increased
with NO  and CO receiving the  greatest increase (Ref. 97).
       /\
These data indicated  that intentional maladjustment or
defeat of emission controls resulted in significant emissions
increases without actual component failures.
          The EPA/CRC CAPE-13-68 study (Ref. 16) included  an
analysis of several common adjustment and component defects
                                                           •
in pre-1972 model-year vehicles.  Variables studied in the
                          2-17

-------
controlled experiment included timing,  idle speed,  idle
mixture, air cleaner restriction,  PCV restriction,  and NO
                                                         A
TCS defeat.  Emissions were reported in  grams  per mile and
were measured using hot start 1972 FTP  tests.   The  data in
Table 2-7 was reported for 1971 NO  controlled vehicles.
                                  J\
Table 2-7.
            EFFECT OF COMPONENT DEFECTS ON HOT FTP EMISSIONS
                       (Ref.  16)

Timing (gm/mi /degree advance)
Idle Speed (gm/mi/100 rpm)
Idle Mixture (gm/mi/% CO)
% Blocked Air Cleaner (gm/mi)
PCV Blocked (gm/mi)
TCS Defeat (gm/mi )
HC
0.08
-0.15
-0.07
0.18
0.36
0.55
CO
-0.90
2.80
6.53
12.42
18.03
-6.30
N0*
A
0.15
0.07
-0.03
-0.48
-0.33
0.99
          All  changes were relatively small  with respect to
the effective  emission standards of 1971  model-year vehicles.
Direct comparison to 1972 and later model-year vehicles is
difficult, however, because these data were  based on hot
start tests and did not reflect changes in engine and
emission control  system design applicable to recent model
years .
          Panzer  (Ref. 12 and 96) discussed  the idle emission
test program performed by Exxon.  The first  paper included a
survey of 23 previous papers relating component defects to
qualitative steady-state emissions (Table 2-8).  No quantita-
tive data based on FTP emissions were presented, however/
XUDStantial HC and CO emission reductions were achieved by
performing adjustments and repairs to correct idle mixture,
engine speed,  timing, PCV system restriction, ignition and
carburetor malfunctions, vacuum leaks and valve leaks.
                          2-18

-------
Table 2-8   EFFECT OF ENGINE VARIABLES ON STEADY STATE EMISSIONS
        FROM PRE-1973 VEHICLES (TABLES 3 AND 4,  REF.  12)
VARIABLE
Increased A/F
Increased RPM
Restricted PVC
Restricted Air Cleaner
Stuck Choke
Carburetor Malfunction
Ignition Malfunction
Retarded Timing
Stuck Heat Riser
Excessive Fuel Pressure
Exhaust Valve Leaks
Vacuum Leaks
Decel Device Failure
Spark Advance Failure
Air Pump
Air Inlet Temp. Increase
IDLE
CO
Decrease
Decrease
Increase
Increase
Increase
Increase
-
-
Increase
Increase
-
Increase
-
-
-
-
HC
Decrease to
Stoichiometric
-
-
-
-
-
Increase
Increase
-
-
Increase
Increase
-
-
-
Slight
Increase
LOADED
CO
Decrease
None
Increase
Increase
Increase
Large
Increase
-
None
-
-
-
-
-
-
Increase
-
HC
Decrease to
Stoichiometric
Decrease
Increase
Increase
Increase
Increase
Increase
Decrease
-
-
Increase
Increase
Increase
Increase
Increase
-
                              2-19

-------
          Several  reports  (Ref.  16,  33,  42,  43,  49,  51,  54,
60, 74, 78, 84, 94,  95,  and 99)  discussed  various  Inspection
and Maintenance (I/M)  studies.   These reports  indicated  that
I/M was effective  in reducing emissions  of HC  and  CO.
Unfortunately, only  a  few  of these studies were  performed  on
catalyst-equipped  vehicles and  none  associated emissions
increases or decreases to  individual  component defects.
          Springer (Ref.  63) reported extensively  on smoke
emissions from diesels.   Control  of  smoke  emissions  were
primarily due to modifications  to injector pumps,  injector
tips, spray pattern, duration and timing.   In  some appli-
cations, introduction  or  modification of turbochargers
redu.ced smoke.  Control  requirements  for NO  ,  however,  tend
to increase smoke  emissions due. to premature flame quenching
in the cooler combustion  gases.   Control  of  smoke  from  in-
use vehicles, however, is  more  related to  engine power
derating, retrofit components,  or modified driver  operating
procedures.  Except  in severe conditions,  normal maintenance
generally did not  make significant changes in  smoke  emissions,
providing that basic adjustments  of  the  fuel injection
system were made to  manufacturer's specification.
2.3       PROBABILITY AND DURATION OF COMPONENT FAILURE

          Several  of the references describing emissions
characteristics of defective components  also provided data
on failure rates of components or systems.   No data,  however,
was obtained regarding probable duration of failure,  although
most sources implied a st-rong relationship  between performance
degradation and corrective repair.  However, in practice,
driver sensitivity to, and tolerance of, performance  degrada-
tion varies and depends, in part, on the nature and severity
of degraded performance, vehicle age, and the imagined or
real cost of repair.
                          2-20

-------
          Inspection and Maintenance (I/M) studies provided
some data on the incidence of system failures in the vehicle
population.   Unfortunately, the failure criteria and the
observed failure rates varied considerably.   Most studies
related failure criteria to modal  emission characteristics
(Ref. 33, 42, 43, 49, 60, 79, 84,  94,  95,  and 99).  These
studies identified high incidences of  incorrect basic idle
adjustments.  Other studies which  involved parameter inspec-
tion or performance criteria generally detected more component
failures than the emission inspection  studies (Ref.  16,  78,
101, and 102).
          The observed failure rates,  regardless of  the
inspection -criteria and methodology, reflect an average  of
continually  occurring component failures and repairs.
Therefore, using inspection data to define component failures,
may not truly reflect the probability  of an  individual
component failing.  It only represents the probability  of
finding defects at any one time in a vehicle population.
The true failure rate is, therefore, likely  to be higher
than detected for components which are likely to be  repaired.
The failure  rate is likely to be about the same as indicated
for components which are not likely to fail  or be repaired.
          Panzer (Ref. 12) summarized  several prior  studies
in addition  to data from the Exxon Research  idle fleet.   This
data is presented in Table 2-9.
          Catalyst durability studies  provided some  data on
component failure as described in  Section  2.2.  The  NAS
summary document (Ref. 70) provided preliminary data on  mean
time to failure or suggested maintenance intervals for  some
selected components.  These data are shown in Table  2-10.
          Catalyst durability studies  also showed that
ignition defects severe enough to  cause catalyst malfunction
occurred on  only 3 to 5 percent of the vehicles.  Other
component failures were not described  because they generally
did not occur or they did not adversely affect catalyst
life.
                            2-21

-------
   Table 2-9.   INCIDENCE OF MALFUNCTIONS
(ABSTRACTED FROM TABLES 7 AND 8 OF REF. 12)
DESCRIPTION
Ignition
Mixture
Engine RPM
Carburetor
Choke
Timing
PCV Valve
Air Filter
Vacuum Leak
Heat Riser
Vacuum Advance
Air Pump
ALL VEHICLES
Survey
( Percent )
4-78
60
70
24
-
76
-
-
-
9
-
11
Exxon
( Percent)
12 - 18
26 - 40
38 - 55
4 - 10
1 - 4
4 - 27
1 - 4
1 - 5
1 - 2
11 - 3
1 - 4
-
REJECTED VEHICLES
Survey
(Percent)
12 - 30
-
-
15 - 20
-
-
-
-
-
-
-
•
Exxon
( Percent)
51
28
38
17
13
10
7
6
6
0
1
-
                    2-22

-------
Table 2-10.
ESTIMATED DURABILITY OF AUTOMOITVE PARTS
    (TABLE 13 OF REF. 70)
SYSTEM PARAMETERS
Carburetion
A/F at idle
A/F at main jet
A/F power jet
Choke
Heat Riser valve
Altitude compensation
Leaks intake manifold
Leaks vacuum line
Air cleaner - plugged
Ignition
Misfire—plugs
Misfire—wiring
Misfire— cap and rotor
Basic timing
Automatic spark advance
Devices
PCV system
EGR system
Air pump system
Oxidation catalyst
Reduction catalyst
Evaporative control system
Other
Idle speed
Burned exhaust valve
Low compression
MEAN TIME-TO
FAILURE (MI)
Scott
Labs.

15,000
30,000
—
25,000
25,000
—
50,000
35,000
20,000

20,000
25,000
30,000
15,000
25,000

30,000
--
40,000
25,000
25,000
70,000

15,000
90,000
60,000
American
Motors

25,000
--
--
25,000
5,000
--
50,000
50,000
15,000

15-30,000
50,000
50,000
15,000
100,000

15,000
12-50,000
100,000
12,000
__
50,000

15,000
100,000
100,000
SERVICE
INTERVAL (MI)
Chrysler

12,000
12,000
12,000
6 months
6 months
—
—
Infrequent
12,000

18,000
Infrequent
Infrequent
12,000
12,000

12,000
12,000
12,000
__•
__
12,000

12,000
Infrequent
Infrequent
                         2-23

-------
          A consultant report to the NAS (Ref.  73)  described
some probable maintainability and reliability data  for 1975-
1976 configuration vehicles:

          •    EGR maintenance should be reduced by lead-
               free fuel  because particulate (deposits)
               emissions  are  reduced.

          •    Spark plug life should be increased  by lead-
               free fuel  and  high energy ignition system.

          •    Ignition wire  life should be  increased by
               improved insulation and conductor materials.

          •    Heat riser service interval  should be extended
               four to five times due to lead-free  fuel.

          t    Electronic ignition should minimize  changes
               in spark timing and firing due to point
               failure, thereby reducing misfire.

          •    Vacuum line, vacuum motor, vacuum diaphragm,
               and exhaust pressure diaphragm malfunction
               should be  low  (fraction of 1  percent in the
               vehicle population).

          The California  Bureau of Automotive Repair reported
the failure incidences at the Vehicle Inspection Facilities.
in Riverside (Ref. 94).  These data are reported in Table 2-11
and include about 900 failed  vehicles.  The  decision on
whether repairs were required were based on  an  engineering
evaluation of ignition and emission data before and after
maintenance.  In general, a low incidence of ignition mal-
functions were found with most failures due  to  idle adjustments
and off idle carburetion  problems.
                          2-24

-------
Table 2-11.   REPAIRS PERFORMED DURING CALIFORNIA VEHICLE EMISSION INSPECTION
             PROGRAM (ABSTRACTED FROM TABLES 13 THROUGH 21, Ref. 94)
          DESCRIPTION
PERCENT OF FAILED
VEHICLES RECEIVING
      REPAIR
PERCENT OF FAILED
VEHICLES REQUIRING
      REPAIR
 Idle Adjustment
 PCV Filter Replacement
 Choke Adjustment Repair
 Carburetor Overhaul (Kit)
 Carburetor Replacement
   (New or Rebuilt)
 Air Filter Replacement
 Spark Plug Replacement
 Point Replacement
 Condenser Replacement
 Rotor Replacement
 Ignition Wire Replacement
 Heat Riser Repair
 Heated Air Inlet Repair
 Air Injection System Repair
 Compression Check for Engine
   Defects
 Other Repairs (Mechanical,
   Miscellaneous, Ignition,
   Vacuum System, etc.)
       100
         2
         3
        16

         4
        13
        12
        12
        10
         4
         5
         1
        82
         2
         3
         8

         1
         3
         3
         2
         2
         1
         3
         1
                                  2-25

-------
          The CARB reported on the incidence of failures
found in low mileage catalyst vehicles which failed an idle
HC screening standard (Ref. 93).   These data are reported in
Table 2-12.  The determination of whether a defect existed
or not was based on a diagnosis performed by CARB  technicians
   Table 2-12.  INCIDENCE OF DEFECTS IN LOW MILEAGE
              CATALYST VEHICLES (REF.  93)
DEFECTS
Ignition Misfire
Mi xture
Engine Speed
Carburetor
Choke
Timing
PCV Valve
Air Filter
Vacuum Leak
Heat Riser
Vacuum Advance
Air Pump/Hose
EGR Failed/Defeated
Thermal Air Cleaner
Catalyst
Other Defects
PERCENT OF
FAILED VEHICLES
12
15
9
3
9
15
3
30
12
0
3
15
15
6
3
18
PERCENT OF
ALL VEHICLES
0.8
1.0
0.6
0.2
0.6
1.0
0.2
2.0
0.8
0
0.2
1.0
1.0
0.4
0.2
1.2
2.4
SALES VOLUME
          Data on the sales volume of emissions-related
components was not available in a form useful  to this study
Therefore, the component usage information described in
Section 2.1 was combined with data on engine family
sales volume and recommended replacements of each component
to estimate the probable component sales volume.
          The scheduled replacement intervals  were obtained
from the manufacturer's recommended maintenance schedules.
In general, the same maintenance schedules applied to all
engines produced or sold by each vehicle manufacturer.
                          2-26

-------
          Sales information by engine family was obtained
from production data submitted to the EPA by Ford, General
Motors, Chrysler, and American Motors Corporation for the
1975 and part of the 1976 model-year.  Data was requested
directly from the major manufacturers, but the requested
                                      A»
data was not submitted to Olson.  Supplimental data on produc
tion volume of vehicles by make, model,  and model-year were
obtained from the Automotive News Yearbooks for 1974 and
1976 (Ref.  26) and from the Automotive Industries Statis-
tical  Issues for 1975 and 1976 (Ref. 103).
                         2-27

-------
                        Section  3

              EMISSIONS-RELATED  COMPONENTS
          This section  describes  the  emissions-related
systems and their components.   Functions,  typical  appli-
cations and characteristic modes  of failure  are  described.
The systems and components discussed  in  this Phase I  report
consist of those installed as  original  equipment on  new 1972
and subsequent model-year engines and vehicles.   A list of
the components determined to be emissions-related  is  pre-
sented at the end of this section.
3.1       CRITERIA AND ASSUMPTIONS

          Emissions-related systems,  parts,  and  components
were defined by the study contract to be emissions-related
if they had to be built to certain specifications  and/or
perform within certain specifications, or one or more
pollutant (HC, CO, NO , smoke)  would  exceed  applicable
                     A
standards for the vehicle or engine.   This definition was
sufficiently broad to include essentially all engine and
emission control  systems used on vehicles.
          For the purpose of this study, "original  equipment"
included all systems, parts, and components  installed in new
vehicles and engines by or for the vehicle or engine manufac-
turers in compliance with regulations issued under Title II
of the Clean Air  Act.  Under this contract original  equipment
also included those replacement parts which  were identical
                         3-1

-------
to factory installed components and were built by or for the
vehicle or engine manufacturer.  To simplify the analysis,
this definition was interpreted to mean all  replacement
parts or components distributed by the original  vehicle/engine
manufacturers through their dealer or authorized service
center networks.
          Although the contract defined emissions-related
parts to be those whose failure would cause  violation of
emissions standards, it was not possible to  determine from
the literature or engineering analysis if all  of the component
defects would cause an emissions failure.  This  was  because
even though emissions might be doubled, low  emitters might
still pass the standard.  Therefore, rather  than arbitrarily
exclude a component from further consideration because its
failure was assumed not to cause emissions failure,  all
components with potential  effects on emissions were  considered
This included components whose failure affected  the  operation
of other components.
          To facilitate the analysis, individual parts with
similar design and function were grouped together into part
categories (i.e.; spark plugs, air filters,  thermal  vacuum
valves, etc.).  Individual components within each part
category were then assigned average parameter  values repre-
sentative of typical components included in  that category.
Assignment of specific values for each input parameter is
described in Section 4.
          In order to assign specific values to  the  input
parameters, it was necessary to define a typical failure
mode for components in each category.  For most  components,
individual design, fabrication, assembly, and  application
characteristics could differ depending on manufacturer and
model resulting in a different failure mode  or failure
threshold for individual components within each  category.
However, since the scope of this study could not include all
                          3-2

-------
individual  components,  it was  necessary to  select representa-
tive components from each category and  to define the charac-
teristic failure modes  for that component.
          Several  component categories  within  emission
control  systems use similar components  (i.e.;  thermal  vacuum
switches, vacuum hoses, speed/transmission  sensors).  These
components  were assigned identical failure  modes and probabil-
ities of failure even though they were  used in different
applications.   Emissions increase and probability of repair
factors  may have been different, however, depending on the
application.
          Engine and emission  control components are function-
ally or  physically related to  other specific components.
This permitted the grouping of related  categories of components
into subsystems and major functional  systems.   Each system
and its  component  parts were assigned a part code number
based on the following  system:

               X.   XX.   XXX
                          _ Part Category Code
                    — Subsystem Code
               i-Major  System Code
          The part code system provided a systematic method
of compiling and processing the data.   The relationship of
emissions to the following major systems and their respective
components are discussed in this Section:

          •    Carburetion system
          •    Ignition system
          •    Air induction system
          0    Fuel injection system
          •    Miscellaneous engine systems
          t    Emission control systems
                         3-3

-------
          The literature surveyed in Section 2 and an engi-
neering evaluation formed the bases for the discussion
presented below.
3.2       CARBURETION SYSTEM

          The carburetion system is responsible for correctly
metering the required amount of fuel  to the engine.  Carbure-
tion systems depend upon relatively complex mechanical  and
vacuum controls which, if defective,  can severely impair the
functioning of the overall  system.   For purposes  of this
study, the carburetion system was  divided into the following
three subsystems:

          •    Complete carburetor  assemblies, either new or
               rebui11.
          •    Carburetor control  devices external to the
               carburetor itself which  modify the carburetor
               performance  under special operating conditions
          t    Individual carburetor  components.

          In general , carburetor components and control
devices can be associated with either closed-throttle (idle)
or open-throttle (acceleration or  cruise) operation.   The
certification test for light-duty  vehicles (1972  FTP  and
1975 FTP) contains substantial idle operation.  However,
defects in cruise or  power  circuits can result in very  high
mass emissions due to the high exhaust  flow rate  under  these
operating conditions.  The  certification test results are
also highly dependent on cold start emissions and rapid
warm-up.  Therefore,  defects which  result in delayed  or
improper choke opening can  cause substantial emission
increases.
                         3-4

-------
          Carburetion system defects generally result in
excessively rich operation which leads  to high CO emissions
and occasionally high HC if the CO increase is severe enough
Typical  defects resulting in rich operation include the
following (Ref. 2 and 3):

          •    Improper choke setting or rate of opening.
          t    Ruptured power valve (economiser) vacuum
               diaphragm.
          •    Worn or improperly set metering rods.
          •    Improperly set or defective float and  needle
               valve.
          •    Improper idle adjustment.
          •    Defective idle stop solenoid,  throttle
               positioner, or dashpot.

          Some component defects can cause lean  operation
resulting in misfire (Ref. 2 and 3).  The misfire may be
detected by performance (stumble and hesitation) or by
excessive HC emissions.  These components include:

          •    Worn accelerator pump plunger.
          •    Ruptured accelerator pump vacuum  diaphragm
               (i f  equipped).
          •    Worn or broken gaskets.
          •    Ruptured vacuum diaphragms.
          •    Improper idle adjustment.
          t    Improperly set float level.
          o    Improperly set metering  rods.
          •    Restricted fuel filter.

          In general, defects leading to rich operation are
associated with open-throttle conditions and  contribute high
mass emissions.  Exception to this include grossly rich idle
                         3-5

-------
mixture.   Defects leading to lean operation tend to be
associated with closed-throttle conditions (i.e., high
manifold  vacuum) which are intermittent and contribute low
mass emissions.  Therefore, defects in carburetor components
causing rich operation generally result in substantial CO
mass emission increases while components causing lean oper-
ation usually result in marginal HC mass emission increases.
          The effect of carburetor defects on NO  emissions
                                                ^
are inversely related to the effect on CO emissions (Ref. 2)
Rich operation resulting in high CO will generally result
in reduced NO .  Lean operation resulting in  high HC may
             /\
also result in increased NO  due to higher combustion
                           A
temperatures and mass flow rate because the throttle must be
held open further to compensate for the power loss resulting
from misfire.  However, since conditions where lean misfire
occur are usually intermittent or at closed throttle, the
effect on NO  may be negligible.

3.2.1     Complete Carburetors

          Complete carburetors, either new or rebuilt, are
sold ready for installation on the vehicle.  All necessary
interface and accessory components, incl-uding gaskets,
dashpots, choke, and throttle linkage are generally provided
with the  carburetor.  Considerable data has been generated
which indicates that the metering accuracy and reliability
of new carburetors built and distributed as OEM or OEM-
replacement carburetors are generally better  than factory
rebuilt carburetors or carburetors repaired by mechanics.
Therefore, separate part categories have been defined.for
OEM (new) and after-market (rebuilt) carburetors.
          Carburetor performance can affect all three pol-
lutants,  although CO is usually most sensitive to defects or
improper  adjustment.  Gross carburetor malfunction is
                          3-6

-------
usually associated with one or more of the following com-
ponents (Ref.  2, 3, 16, 78, and 27):

          t    Choke
          t    Power valve
          t    Metering jets and rods
          t    Float adjustment
          t    Accelerator pump
          •    Idle adjustment
          t    Gaskets

          Other components can also increase CO emissions
under certain  operating conditions  or  circumstances.  The
actual  impact  of each defect depends  on the engine and
carburetor under consideration.
          Since each of the above components is individually
repairable, they have been treated  individually in this
study.

3.2.2     Carburetor Control Devices

          Several  emission control  devices have been developed
to regulate or modify the carburetor's operation under
certain operating  conditions.   These  devices generally
regulate throttle  closure in such a way as to modify the
normal  fuel-metering characteristics  of the vehicle.  Defects
in these devices can increase  HC and  CO emissions but the
increases are  generally not as severe  as from fundamental
carburetor defects.

3.2.2.1   Idle-Stop Solenoid

          The  idle-stop solenoid is used on most 1972 and
later model-year vehicles.  The idle-stop solenoid is a  two-
position electrically-operated valve,  used to provide a
predetermined  throttle setting.  The  solenoid becomes ener-
gized when the ignition key is turned  on.  When energized,
the plunger extends and contacts the  carburetor throttle
                          3-7

-------
lever preventing full  closing of the throttle plates.   When
the solenoid is de-energized (plunger retracted), the  throttle
plates close beyond the normal  idle position.  This action
shuts off carburetor air supply, starving the engine so that
it will  shut down without dieseling (Ref. 3 and 27).
          For precatalyst-equipped vehicles, the idle-stop
solenoid is primarily  a performance-related device to  ensure
that the lean calibrated carburetors used in these model-
years did not promote  dieseling of the engine and subsequent
customer complaints.  However,  for catalyst-equipped vehicles,
the idle-stop solenoid becomes  important as a catalyst
protection device to prevent excess fuel flow and subsequent
catalyst overheating during engine shut down (Ref. 27).
          Defects in the idle-stop solenoid would involve
shorted  or open windings in the solenoid which prevent
extension of the plunger.  This would prevent opening  of the
throttle causing slow  and rough idle.  Excessive throttle
opening  and throttle operation  by the driver would be  required
to maintain satisfactory idle performance.   This defect
would increase HC and  CO emissions during closed throttle
operation.

3.2.2.2    Throttle Dashpot

          The throttle dashpot  is generally used on imported
vehicles and some domestic vehicles with manual transmission.
The dashpot is a mechanical device which acts as a damper to
prevent  too rapid throttle closure.  This device can be used
to prevent stalling and/or to reduce emissions by reducing
the momentary rich condition caused when a  throttle is
closed rapidly (Ref. 3 and 27).
          Failure of the dashpot is usually due to deteriora-
tion of  seals.  This results in too rapid throttle closure
leading  to higher HC/CO emissions during deceleration.
                         3-8

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3.2.2.3   Throttle Positioners

          Throttle positioners are used to hold the throttle
slightly open during deceleration to provide a  more combustible
mixture to the engine and, thus,  reduce emissions.   An
additional control device is generally provided to  allow the
throttle to close to normal  idle  position after a certain
length of time, or when vehicle speed decreases to  a certain
point.  These devices are usually operated electrically but
may be vacuum operated (Ref. 3 and 27).
          Throttle positioners are active devices which
perform a function similar to the passive dashpot described
in the preceding paragraph.   Throttle positioners are used
on some domestic and foreign vehicles for improved  HC/CO
emission control.  They can  be regulated more precisely than
dashpots using electrical sensors for speed, temperature,
vacuum, etc.
          Failures of the electrically operated throttle
positioner are similar to the idle-stop solenoid.  If vacuum
operated, failures are generally  associated with ruptured
diaphragms.  Both failures result in normal closed  throttle
operation during all temperature  and speed conditions.
Temperature and speed sensors for the throttle  positioner
are usually associated with  systems to modify timing and are
discussed under TCS or EGR.

3.2.3     Carburetor Components

          The following carburetor components are grouped
together because they can be clearly distinguished  as separate
components, are readily replaceable, and are routinely
adjusted or repaired by mechanics.  A carburetor malfunction
is generally attributable to a defect or maladjustment of
one or more of these components.
                         3-9

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3.2.3.1   Metering Jets

          Metering jets are calibrated orifices through
which fuel passes in response to the vacuum created by the
carburetor venturi .   The metering jet may be located in the
venturi or near the  float chamber.   The jets generally
control fuel  metering from about 1/4-throttle opening to
about 3/4-throttle opening.  Over extended periods of opera-
tion, the throttle jet can erode due to the passage of fuel
resulting in  fuel enrichening (Ref.  2 and 3).  This results
in increased  CO and  possibly HC emissions.

3.2.3.2   Metering Rods

          Some carburetors use metering rods instead of, or
in addition to, metering jets.  The  metering rod is a variable
diameter rod  which moves in and out  of the jet to cause
different effective  orifice sizes.   The metering rod is,
therefore, better able to control fuel metering to variations
in throttle position or vacuum.  Metering rods are moved by
mechanical linkage to the throttle  or by vacuum diaphragms.
          Metering rod accuracy is  strongly related to
position of the rod  in relation to  the load condition.  Rod
position determines  fuel metering at the particular throttle
opening.  Therefore, the characteristic defect defined for
metering rods will be incorrect positioning, resulting in
excessive metering of fuel at all off-idle load conditions.
This results  in higher CO and possibly HC emissions (Ref. 2,
3, and 27).

3.2.3.3   Vacuum Break Valves

          Vacuum break valves, also  called vacuum kick or
choke pull down valves, are used on  most carburetors to
modulate the  choke position.  The ba-sic choke position is
                          3-10

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determined by the choke thermostat as described in paragraph
3.2.3.4.  The vacuum break valve is used  to adjust the choke
position to suit actual load condition as reflected by
vacuum.  Under high vacuum (i.e.,  idle),  the vacuum break
valve opens the choke slightly to  gradually lean  out mixture
as soon as the engine starts.   However, at low vacuum
(i.e., open throttle and moderate  load),  the vacuum break
valve will again close the choke so that  a richer mixture
during the heavy load is provided  to prevent stalling.
          Defective vacuum break valves will result in
normal choke opening causing higher CO emissions.  The
typical failure mode is a ruptured vacuum diaphragm.  This
may result in lean misfire at  idle due to a vacuum leak,  as
well  as the overall rich condition (Ref.  2, 3 and 27).

3.2.3.4   Choke Thermostat and Linkage

          All carburetors employ a choke  which restricts
airflow into, the engine during cold starts.  Since emission
control is very dependent on correct choke operation, automa-
tic chokes have replaced manually-operated chokes on most
emission-certified vehicles.  The  automatic choke is activated
by a  thermostatic coil spring  which unwinds as heat is
applied.  As the spring unwinds, it causes the choke valve
or plate to open permitting proportionally more air to enter
the carburetor.  The fully-open choke does not restrict
airflow and, therefore, normal fuel metering is accomplished
by the idle and cruise circuit of  the carburetor.
          Choke failures are often due to sticking linkages
which cause the choke to remain either open or closed.  An
open  choke will cause poor starting, idle running, and
driveability during cold starts and will  usually  be corrected.
A closed choke may cause excessively rich mixtures (10 percent
CO),  particularly under part throttle loaded operation, and
may not be detected by driveability problems.  Very rich
                         3-11

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mixtures can also cause moderate increases  in  hydrocarbon
emissions (Ref.  2, 3, 16,  78,  and 103).
          Other  choke failures may be due to broken  choke
springs, incorrect choke adjustment,  defective vacuum break
unit, or defective choke heater (Ref. 3).

3.2.3.5   Accelerator Pumps

          The accelerator  pump is used on nearly all  carbure-
tors and provides a quick  burst of fuel  during rapid  accelera-
tion.  Without the accelerator pump,  the mixture would lean
out and possibly cause intermittent lean misfire as  shown by
hesitation or stumbling performance.   The accelerator pump
consists of a mechanically-  or vacuum-operated plunger,
check valves, and metering jet.  The  accelerator pump can
cause excessively rich operation and  high CO emissions if it
is improperly adjusted or  if there are defects or wear in
the check valves, metering jet, or vacuum diaphragm.   However,
the probable defect of the accelerator pump will  be  diaphragm
failure (vacuum-operated pump) or pump piston  seal wear.
Both situations  will  reduce  the effectiveness  of the  pump
action leading to lean out and possibly  lean misfire  and
stumble during acceleration.  This will  increase HC  mass
emissions (Ref.  2, 3  and 27).

3.2.3.6   Power  Valves

          The power valve, or  economiser valve, provides
additional fuel  through the  high speed circuit for full
power operation  at wide-open throttle.  The power valve  is
vacuum-, or in some cases, mechanically-operated.  Not all
carburetors, however, are  equipped with  true power valves.
Some carburetors only use  metering rods  (Section 3.2.3.2)
which provide more fuel to the high speed circuit at  wide-
open throttle (Ref. 2, 3 and 27).
                          3-12

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          Power valves open in response to low manifold
vacuum during open throttle operation.   During closed or
part throttle operation, the manifold vacuum increases,
pulling the power valve closed.   Any obstruction in the
vacuum passages or rupture of the vacuum diaphragm causes
the power valve to remain open at all times  and meter exces-
sive fuel under off-idle operation.   The characteristic
defect of power valves are, therefore,  ruptured vacuum
diaphragms leading to high CO mass emissions (Ref. 2 and 3).

3.2.3.7   Gaskets

          Gaskets are used to join the  carburetor to the
manifold and to join together the individual assemblies of
the carburetor.  The gaskets provide an air  seal against the
engine intake vacuum.  Gaskets are subject to thermal  and
mechanical deterioration.  Periodic  tightening of the carbu-
retor mounting bolts are recommended by most manufacturers
to compensate for gradual compression of the gaskets (Ref. 3
and 27).
          Air leaks past defective gaskets can result in
lean misfire and high HC emissions.   In some cases, internal
gaskets can be eroded by gasoline and fuel enrichening can
occur.  Gaskets have complex shapes  and can  be installed
improperly during assembly or repair of the  carburetor.
However, vacuum leaks past defective gaskets are the most
likely failure mode (Ref. 3).

3.2.3.8   Rebuilding Kits

          Rebuilding kits for carburetors normally include
gaskets and replacement parts subject to wear such as needle
valve and seat, power valve and accelerator  pump diaphragms,
dashpot, and small springs and connectors.  Rebuilding kits
are considered an after-market component in  this study even
though some kits are distributed by  the automobile
manufacturers.
                               3-13

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          Rebuilding kits should normally return a carburetor
to "like new" condition.   However, considerable experience
has shown that a large percentage of carburetors rebuilt by
vehicle owners or mechanics using kits did not operate
correctly.   This is generally due to improper or incomplete
cleaning of air bleed passages in the carburetor or incorrect
installation of gaskets or-other components.   Improperly
rebuilt carburetors can have high CO and HC emission  (Ref.
16, 33, and 78).

3.2.3.9   Float and Valve

          The float and valve assembly serve  as the fuel
reservoir for the carburetor.  All the jets (idle, main, and
power circuits) are fed with fuel from the float chamber.
The rate of fuel metering by all circuits depends  on  the
height of the fuel  column which, in  turn, is  controlled  by
the float in the carburetor bowl.  The needle valve for  the
fuel  inlet  is connected to the float so that  additional  fuel
is admitted to the  reservoir as the  float drops (Ref.  2, 3
and 27).
          Over long periods, the float may develop leaks or
the needle  valve and seat may wear so that excessive  fuel
may be admitted to  the reservoir.  This will  result in rich
operation and excessive CO emissions under all operating
conditions.  The float is subject to adjustment and may  be
set incorrectly either during assembly or during repair  or
rebuilding  (Ref. 2, 3, and 78).

3.2.3.10  Idle Adjustment

          Setting idle mixture is a  fundamental tune-up  step
which is usually specified, although not always performed.
Idle  adjustment affects idle HC and  CO emissions.   Low idle
                          3-14

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emissions tend to give lower FTP emissions  although  statistical
correlation between the measurements  is  poor (Ref.  60 and 84).
The idle adjustment usually regulates bypass (bleed)
airflow which is introduced below the closed throttle plate
to mix with idle fuel  flow.  The idle mixture screws  provide
a convenient method to adjust each vehicle  for optimum idle
operation under actual operating conditions.  It also provides
compensation for clogged or restricted idle air or  fuel  jets
(Ref.  2 and 3).
          The idle emissions are poorly  correlated  to FTP
emissions because most of the mass flow  of  the FTP  emissions
are provided by the main or power valves.   Therefore, the
idle mixture may be lean while the FTP emissions are  high
due to choke or power  valve defects.   Similarly, the  idle
mixture may be excessively rich but the  FTP emissions satis-
factory because of lean cruise operation.   Inspection and
maintenance studies, however, show that  most vehicles with
incorrect idle adjustment are set rich resulting in  high CO
and, in some cases, high HC emissions (Ref. 12, 16,  33,  74,
90, 94, and 99).

3.2.3.11  Idle Enrichment System

          The idle enrichment system, used  on a few  engines,
provides additional vacuum-operated choking during  cold
starts.  This system consists of an air  bleed on the  carburetor
which  is closed by a solenoid and a thermal vacuum  valve.
The thermal vacuum valve responds to  coolant temperature to
disable enrichment during hot starts.  The  solenoid  valve is
activated by the starting circuit and a  timer which  holds
the solenoid open for  35 seconds.  This  system was  utilized
to prevent engine stalling while cold.  Failure of  the
system is most likely  to defeat the enrichment process.
Therefore, an increase in HC emissions might result  from the
system due to lean misfire when cold  (Ref.  27).
                          3-15

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3.2.4     Fuel  Filter

          The fuel  filter is used to remove any entrained
particles and dirt  in the fuel.   If the filter was missing,
foreign particles could lodge in the fuel  metering passages
of the carburetor and affect operation.  By itself, however,
the fuel  filter does not have a  significant impact on emis-
sions unless it becomes so clogged as to restrict fuel  flow
                            i
(Ref. 2 and 3).  Under this condition, the fuel filter  could
result in excessive HC emissions due to misfire.   Although
unlikely, this  has  been observed in some surveillance and
inspection/maintenance programs.  Therefore, the  failure
mode for  fuel filters is flow restriction  leading to lean
misfire.
3.3       IGNITION SYSTEM

          Ignition component defects are generally related
to increased HC emissions resulting from misfire (Ref.  12,
16, 33, 74,  78, and 100).  In some cases (i.e.,  distributor
advance mechanisms), the component performance may affect
NO  because  of changes in ignition timing (Ref.  17, 92,
  /\
and 98).  Specific individual components within  each category
do not have  identical  design or performance characteristics.
However, the general component descriptions, functions  and
modes of failure are presented below for the following
ignition system components:

          •     Points
          •     Condenser
          •     Distributor cap
          t     Distributor rotor
          •     Mechanical advance
                         3-16

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          •    Vacuum advance
          •    Distributor drive
          t    Dual  diaphragm distributors
          •    Spark delay valve
          •    Magnetic/Optical  triggers
          •    Spark plugs
          •    Ignition wires
          •    Coils
          •    Capacitive discharge  systems
          •    Ballast resistor
          •    Electronic ignition  circuits
          •    Glow  plug
          •    Ignition timing adjustment

          These components are generally  grouped  into  primary
(low voltage)  or secondary (high  voltage)  circuits.   In
general, secondary ignition components  (spark  plugs,  wires,
distributor cap and  rotor) cause  misfire  in  specific  cylin-
ders.   Complete misfire on one plug  may  be  due  to  a  fouled
plug or shorted ignition wire.  Intermittent misfire,  which
is more likely, can  occur under  certain  operating  conditions
depending on plug gap and condition,  mixture richness, wire
resistance, and engine speed.  Intermittent  misfire  may  not
be noticeable  by the driver but  may  cause  increased  HC
emissions.   The emissions increase  depends  on  the  number of
cylinders,  misfire frequency, engine  speed,  and whether  air
injection and  catalytic emission  control  system are  present.
         . Primary ignition components include  points,  conden-
ser, advance mechanisms, coils,  capacitive  discharge  systems,
ballast resistors, and electronic ignition  components.
                t
Primary ignition system defects  may  cause  random  intermittent
misfire on  all  cylinders.  However,  in  practice,  misfire
will characteristically appear on the cylinder  with  the
weakest secondary ignition components.   Misfire is caused by
faulty coil, points, and electronic  ignition components
                         3-17

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because insufficient voltage and current is supplied to the
spark plug.  High HC emissions can also be caused without
actual  misfire if the timing of spark plug firing is incorrect
(Ref. 16, 17, 92, and 99).   In these cases, the advance
mechanisms, basic timing,  or distributor cap/rotor may be
faulty.

3.3.1     Points

          The points constitute a switch which  energizes  the
primary circuit of the coil.  As the points make contact,
current flows through the  coil creating a magnetic field.
As the  points open, the current flow stops and  the magnetic
field collapses creating a  high voltage surge  in the secondary
system.  The points wear mechanically and may  also erode
electrically due to improper alignment, polarity, or condenser
capacitance.  As the gap between the points open, they may
no longer make sufficient  contact to adequately charge the
coil.  The low voltage may  then cause intermittent misfiring
of the  spark plugs and increased HC emissions  (Ref.  2  and 3).

3.3.2     Condensor/Capacitor

          The condenser is  a capacitor which prevents  an
electrical arc across the  points as they open.   The  condenser
absorbs the current flow until the points are  fully  open.
Arcing  of the points results in an electrical  erosion  or
transfer of material from  one point to the other.  Condensers
normally are very durable  but are routinely replaced as a
preventative step at each  tune-up.  They are emissions-related
because of their effect on  coil and point life  (Ref.  3).
                         3-18

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3.3.3     Distributor

          The ignition distributor controls  the  making  and
breaking of the primary ignition  points  and  distributes the
high voltage current to the proper spark plug  at the  correct
time.  Detailed construction of distributors varies  consider-
ably between manufacturers.  Basically,  however, each can  be
divided into the following categories:

          •    Cap
          •    Rotor
          t    Mechanical  advance
          t    Vacuum advance
          •    Distributor drive
          •    Dual  diaphragm distributor
          t    Spark delay valve.

3.3.3.1   Cap

          The cap provides terminals  for connecting  the
spark plug wires and the rotor contact.   The terminals  in
the cap are subject  to corrosion, wear,  and  electrical
erosion due to arcing.  This deterioration  can reduce the
peak voltage and duration  of the  secondary  current.   It is
also possible for conductive trails to  be formed between
contact terminals of the cap resulting  in crossfiring of the
wrong spark plug.  Either  situation causes  intermittent
misfire, thereby, increasing HC emissions (Ref.  2 and 3).

3.3.3.2   Rotor

          The rotor  is a rotating conductor  which distributes
the high voltage current to the correct  spark  plug by contact
ing the corresponding terminal in the base  of  the cap.   The
contact terminal of  the rotor is  subject to  wear and  erosion
                         3-19

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as are the terminals of the cap.  As the rotor wears, the
resistance of the circuit increases which reduces peak
voltage and firing time.  These, in turn, may result in
misfire and excessive HC emissions (Ref. 2 and 3).

3.3.3.3   Mechanical Advance Mechanism

          The mechanical advance mechanism, also called
centrifugal advance, regulates the time at which the points
open and close relative to the position of the piston in the
cylinder.   The mechanical  advance provides an earlier spark
firing at  high rpm because the time available to burn the
charge is  shorter at high speed than low speed.   The advance
mechanism  consists of two weights held by springs which are
thrown outward from the distributor shaft by the centrifugal
force of the rotating distributor.  The faster the  distributor
shaft rotates, the greater the movement of the advance
weights.  The movement of the weights  rotates the breaker
plate containing the points and changes the time at which
the points make contact.  The mechanical advance unit is
very durable and generally does not need to be replaced or
serviced over the life of the vehicle.  However, failure of
the advance mechanism can occur due to broken or weakened
springs which will alter the ignition  timing and affect HC
and NO  emissions (Ref. 2 and 3).
      J\

3.3.3.4   Vacuum Advance Mechanism

          The vacuum advance mechanism provides  the same
function for vacuum as mechanical advance does for  engine
speed.  The intake manifold vacuum is  transmitted to a
diaphragm  connected to the breaker plate.  The diaphragm is
spring-loaded and airtight on one side, and open to the
vacuum line on the other.   As vacuum increases,  the diaphragm
deflects and moves the breaker plate via connecting linkage
(Ref. 3).
                          3-20

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          The ignition advance affects  both HC and NO  emis-
                                                     /\
sions (Ref. 16, 17, and 99).   Because vacuum advance can be
easily modulated by controlling the vacuum signal, vacuum
control  valves are an integral part of  emission control
systems.  In general, vehicles manufactured after 1972 have
used modulated vacuum advance as part of the NO  control
                                               A
system.   The systems and components which control vacuum are
discussed in the section on emission control systems.
          Vacuum advance systems fail more frequently than
mechanical  advance due to fatiguing of  the diaphragm and
subsquent failure to correctly adjust timing to vacuum
changes  (Ref. 78).

3.3.3.5    Distributor Drive Mechanism

          The distributor drive consists of the distributor
shaft, cam, and breaker arm.   The distributor shaft is
connected directly to the engine and is driven aty/frTe engine
rpm.  The distributor shaft rotates the cam which has one
lobe for each cylinder.  The  breaker arm is held against the
cam by spring tension.  As the cam rotates, the breaker  arm
rides in and out on the lobes.  The point mounted on the
breaker  arm then makes and breaks contact with the stationary
point (Ref. 3).
          Mechanical wear of  the distributor shaft, bearings,
bushings, cam lobes, and breaker arm all cause deviation
from specification of point opening and closing.  The
deviation may be consistently on one cylinder (defective cam
lobe) or randomly on all cylinders (defective bearings).
This deterioration can result in intermittent misfire and
excessive HC emissions (Ref.  3).
                          3-21

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3.3.3.6   Dual  Diaphragm Distributor

          Some  vehicles are equipped with dual  diaphragm
distributors which are similar to standard distributors
except that two vacuum advance diaphragms are provided.
This distributor allows the spark timing to be  retarded in a
normal manner during starting.  During acceleration  and part
throttle cruise, the spark timing is advanced in a  normal
manner.  However, during idle and deceleration, the  timing
is retarded even more than would normally occur.  This
provides HC emission control  during idle and deceleration  by
encouraging higher engine rpm and smaller quench volume in
the cylinder at the time of spark firing.  Failure  of either
diaphragm will  effect emissions of HC and CO (Ref.  3 and 27)

3.3.3.7   Spark Delay Valve

          The spark delay valve, used on some engines,  aids
in control  of HC and NO  emissions by delaying  vacuum spark
                       A
advance during  light acceleration.  Immediate spark  retard
is still permitted during deceleration.   The valve  controls
vacuum by means of an integral sintered  metal disk  and  check
valve.  The delay valve is connected in  the vacuum  line
between the carburetor spark  port and advance diaphragm of
the distributor.  Several different valves are  used  which
provide slightly different delay times depending on  engine
application.  Failure of the  valve occurs when  the  check
valve fails to  seal.  In these conditions, normal  spark
advance is  provided which can increase HC and NO  (Ref. 2, 3
and 27).
                         3-22

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3.3.4     Magnetic or Optical  Triggers

          Electronic ignition  systems  use  either magnetic
proximity detectors or photodiodes  to  indicate  the correct
firing time of each spark plug.   OEM systems  generally use
magnetic systems.   Some after-market systems  which directly
replace the standard breaker points  use  optical  detectors.
The magnetic or optical triggers  are rigidly  mounted  on  a
breaker plate connected to the vacuum  advance unit.   The
distributor cam is replaced by either  magnetic  or opaque
bars mounted on the distributor  shaft.   One  bar  is provided
for each cylinder.  As the distributor  shaft  rotates, the
bars move past the magnetic pickup  or  block  a light  beam
between a lamp and photodiode.  The  magnetic  or  optical
pickup then generates a signal pulse which  is sent to the
electronic ignition control circuit  (Ref.  3  and  46).
          The alignment of the ignition  triggers is  critical
in these systems,  but there is little  wear  or deterioration.
Problems can still develop in  the distributor drive  or
vacuum advance mechanism, however,  since they are identical
to standard units.
          Failures of the electronic triggers are unlikely
and would probably disable the vehicle.   It  is  possible,
however, for deterioration in  a  detector to  cause an  inter-
mittent misfire due to failure to detect one  of  the  bars.
This is analogous  to a faulty  distributor  cam and results in
increased HC emissions.

3.3.5     Spark Plugs

          Spark plugs provide  the gap  in the  cylinder across
which the high tension voltage arcs.  The  resulting  spark
ionizes the charge between the electrodes  of  the spark plug
igniting the combustion process.   A  variety  of spark  plugs
are manufactured with varying  electrical,  thermal, and
                          3-23

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physical  characteristics.   Selection of the correct spark
plug is important since accelerated fouling or deterioration
of the plug can occur if it is  not suited to the application.
          Spark plugs significantly affect HC emissions  due
to intermittent or total misfire of the air-fuel  mixture.
Spark plug performance depends  on gap width which is  dependent
on thermal and electrical  erosion.  Fouling which can be
caused by carbon residue,  lead  residue, or oil  also affects
plug performance (Ref. 2,  3,  16, 42, 43 and 78).
          Spark plugs are  routinely replaced as a preventative
measure every 12,000 miles or 12 months.   Some manufacturers
of 1975 and later model-year  vehicles, however, now recommend
longer replacement intervals  because factors responsible for
plug fouling, such as lead deposits, have been modified  as
part of catalyst and high  voltage ignition system design.

3.3.6     Ignition Wires

          Ignition wires conduct the current from the distrib-
utor cap to the spark plug.  Ignition wires are subject  to
thermal and mechanical deterioration which either increase
their internal resistance  or  decrease the effectiveness  of
their insulation.  Both effects reduce the current and
voltage available at the spark  plug.  The reduced voltage
then causes reduced spark  intensity and intermittent  or
total misfire.  Misfire will  usually occur under load when
the high frequency of coil charging results in lower  average
available voltage to all spark  plugs.  Crossfire or firing
of a cylinder at the wrong time, can also result if two
wires cross and touch each other at a point where their
insulation is defective (Ref. 3 and 78).
                         3-24

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3.3.7     Coils

          The coil  is the OEM high voltage source on most
vehicles.   The coil  is a pulse transformer designed to step
up the primary (12V)  voltage to the high (20,000V to 40,000V)
voltage required to  fire the spark plug.  Failures of the
coil  result in low available voltage to the spark plug and
may result in intermittent misfire particularly at high
speed (Ref. 3, 35 and 78).

3.3.8     Capacitive  Discharge Systems

          Capacitive  discharge (CD) ignition  systems are
sold  for after-market, high performance applications.  A few
high  performance sports cars, however,  are OEM-equipped with
CD ignitions.  The CD ignition provides high  secondary
voltage with very fast rise time.   The  spark  gets to the
plug  faster, and although the voltage is higher, the spark
duration is shorter  which extends  plug  life.   The higher
voltage also is better able to fire fouled plugs than the
standard ignition system (Ref. 3).
          The CD system may utilize either electronic or
breaker point timing.  A transformer is used  to step up the
primary voltage to several hundred volts which is then
discharged through a  standard ignition  coil using a capacitor
switch.  The higher  primary voltage permits lower primary
current flow which extends point life if points are used.
The coil is able to  output a higher secondary voltage which
is then distributed  to the cylinders by a conventional
distributor (Ref. 3).
          Because CD  ignition systems have such limited OEM
usage, they will be  included in Phase II, the after-market
parts, analysis only.
                          3-25

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3.3.9     Ballast Resistor

          In most ignition systems, one and sometimes two
resistors are used.   In standard breaker point systems, the
resistor is in series with the coil during normal  operation.
However, during cranking when the starter motor load reduces
the available voltage, the resistor is bypassed.   The resistor,
therefore, simulates the starter motor load and ensures that
the coil is exposed  to consistent primary voltages.   A
defective resistor will disable the engine, either through an
open circuit or by rapidly burning out the coil.   A  resistor
with low resistance  can also result in burned points (Ref. 2
and 3) .
          Electronic ignition systems  usually use  two resis-
tors, one for the coil and a second one for the electronic
switching circuits.   The coil resistor maintains  stable
voltage  at the coil  and output of the  power transistor.  The
starting resistor performs the same function described above
for the  ballast resistor in a standard ignition system (Ref. 3)
3.3.10    Electronic Ignition Circuits

          The switching and amplifying  circuits  of electronic
ignition systems take the low level  signal  from  the magnetic
or optical  triggers and provide a  5  to  10V  signal  to the  ignition
coil.  The  electronic ignition circuits are generally reliable
and not subject to deterioration unless other  components  in
the electrical  system become defective.  The electronic
circuits will disable the vehicle  if they fail;  therefore,
these components are not emissions-related  (Ref.  3).

3.3.11    Glow Plug

          The glow plug, used in diesel engines,  is a resistor
coil which  becomes hot enough to act as an  ignition source
                         3-26

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for compression ignition  engines.   The  glow plugs  are  turned
on prior to starting a  cold  engine  and  allowed  to  heat the
cylinders for several  minutes.   The engine  can  then  be
easily started.  Without  a  glow plug,  the  engine might not
start when cold.   The  glow  plug, if defective,  can result in
excessive emissions of  unburned fuel  and  smoke  during  cranking
and warm up.   However,  the  heavy-duty  diesel  test  procedures
are conducted with the  engine fully warmed  up so that  the
glow plug is  not  emissions-related  in  terms of  exceeding
emission standards (Ref.  2  and  3).

3.3.12    Ignition Timing Adjustment

          Basic ignition  timing controls  the  moment  at which
the spark plug fires.   Timing is adjusted  at  a  specified
idle engine speed and  is  expressed  in  crankshaft degrees
before or after top dead  center in  the  number one  cylinder.
Timing affects performance,  emissions,  and  fuel economy
because different combustion conditions  occur as timing
changes.  In  general,  advanced  timing  causes  the spark to
fire earlier  in the compression stroke.   This usually  increases
HC (larger quench surface),  reduces CO  (longer  burning
time), and increases NO  (higher mixture  temperature and
                       A
pressure).  Retarded timing  generally  causes  the spark to
fire during the power  stroke at or  after  top  dead  center.
This usually  reduces HC (smaller quench  surface),  increases
CO (shorter burning time),  and  decreases  NO  (lower  mixture
                                           A
temperature and pressure).   Exhaust treatment systems  may
modify the measured exhaust  emissions  by  thermal or  catalytic
oxidation (Ref. 2, 3,  16, 17, 21,  60,  78,  92, 93,  95,  96, 97
and 98).
          Timing  adjustments must  be  made  carefully  to
ensure that the intended  setting is actually  achieved.  This
includes disconnecting  vacuum lines from  the  distributor,
ensuring that idle speed  and mixture  adjustments are correct,
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measuring timing correctly, setting the timing to the correct
specification, and locking the adjustment without altering
it.   The chance of incorrectly setting timing is, therefore,
fairly high (Ref.  2, 3 and 27).
3.4       AIR INDUCTION SYSTEM

          The air induction system includes  the air cleaner,
air cleaner housing, manifolds, superchargers, turbochargers
and associated hoses, ducts, pumps, and vacuum and electrical
controls.  The air induction system can have significant
impact on the air-fuel  ratio and,  therefore, emissions  of
CO, smoke and, to a lesser degree, NO  and HC.
                                     /x

3.4.1     Thermostatically Controlled Air Inlet

          Thermostatically controlled air (TAG) inlets  pre-
heat cold air to promote better fuel  mixing  and vaporization.
The specific design varies according  to manufacturer.   How-
ever, each system uses  some or all of the following components

          t    Shroud and heated air  hose or duct
          •    Thermostat
          •    Vacuum hoses
          •    Fresh air inlet

          Failure of the TAC shroud,  hose, thermostat,
vacuum motor or vacuum hoses will  generally  result in  loss
of heated air during warm-up.  This will have the effect of
reducing the vaporization of fuel  and of increasing the mean
air density during warm-up (Ref. 2).   Both effects will tend
to cause lean misfire and increased HC.  The vacuum hose
failure will also result in a vacuum  leak which would  be
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present at all  operating conditions  and would be expected to
further increase HC emissions.   The  fresh air inlet on some
vehicles extends the snorkel  to the  grill.   This provides
uniformly cool  air in spite of  overheating  of the underhood
air which could occur during  prolonged idle.   This maintains
proper air-fuel ratios by controlling the air density (Ref. 3
and 27).

3.4.1.1   Shroud and Hose

          Cold  air is heated  by passing it  near the exhaust
manifold.  The  shroud is a sheet metal enclosure which
covers the exhaust manifold and directs air along it.  The
duct or hose connects the shroud to  the air cleaner.   The
duct and shroud may become damaged due to maintenance on  the
vehicle which requires removal  of the air cleaner.  This
will probably result in increased HC emissions during the
cold start.

3.4.1.2   Thermostat

          The thermostat is mounted  in the  air cleaner
assembly and controls the opening and closing of a damper
which is used to select either  underhood air  or preheated
air from the shroud.  The thermostat senses incoming  air
temperature and if it becomes too low, will direct preheated
air into the carburetor.  The thermostat may  be directly
linked to the hot air valve or  it may be connected to a
vacuum switch.   Failure of the  thermostat may occur in
either position but is more likely to be stuck open since
               •
this is its usual position.  This will prevent heated air
from entering the carburetor  and have the same effect as  a
damaged hose.
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3.4.1.3   Vacuum Motor and Hoses

          Some systems use vacuum motors to operate the hot
air valve.  The vacuum signal  originates at the manifold and
is transmitted to the vacuum motor by standard vacuum hoses.
The hoses are subject to thermal and mechanical deterioration
The vacuum motor is a diaphragm which moves when vacuum is
applied and is returned by a spring to its original  position
when vacuum is removed.  The vacuum motor is reliable but is
subject to the same diaphragm  failures as any other vacuum
activated device.  Failure of  the vacuum motor or hoses
would result in the engine always receiving cool  air and
would also introduce a manifold vacuum leak when the motor
would normally be activated; i.e., cold start.

3.4.1.4   Fresh Air Inlet

          Beginning with some  1975 model-year vehicles, the
fresh air inlet to the carburetor was moved from the carbure-
tor air cleaner assembly to the radiator grill.  A flexible,
reinforced paper duct is used.   This provides a ram jet
effect to counteract the characteristic of carburetors  to
enrichen the mixture at high airflows.  The air available
at the radiator is also somewhat colder and, therefore, more
dense than underhood air, particularly during low speed
operation when air movement in  the engine compartment is
restricted.  The fresh air inlet is subject to mechanical
and thermal deterioration, especially when inspecting or
servicing the carburetor.  Failure of the inlet duct would
result in hotter underhood air  being drawn into the engine
resulting in slight enrichment  and increased CO emissions.

3.4.2     Air Cleaner Element

          The air cleaner removes particulates in the incom-
ing air and, in some applications, must also remove entrained
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oil  droplets or exhaust particulates  from the PCV system.
The  filter element eventually becomes clogged with material
and  does not allow sufficient air into the carburetor.   This
results in fuel enrichening and excessive CO and possibly  HC
emissions (Ref. 2, 3, 12,  16, 78 and  100).

3.4.3     Manifold-s
          The intake manifold generally is  not changed on a
vehicle except for unusual  cases of manufacturing defects or
to perform after-market, high performance modifications.
Intake manifolds connect the carburetor to  the cylinders  and
provide the ducts to introduce the air-fuel  mixture into
each cylinder.  Some mixing of air and fuel  occurs in the
manifold although this is not subject to maintenance.  The
exhaust manifold connects the exhaust ports  of the cylinders
to the exhaust pipe.  Specific control components of the
manifolds (i.e.; heat risers, cross overs,  EGR valves, and
back pressure sensors), are discussed below  under emission
control systems. There is no specific emissions failure mode
for an OEM manifold (Ref. 2 and 3).  It is,  therefore,
excluded from the OEM criticality analysis.

3.4.4     Turbochargers

          Turbochargers are turbine-driven  blowers which
pressurize the intake manifold in proportion to exhaust gas
flow rate.  This permits higher volumetric  efficiency of  the
engine, particularly during acceleration.  The turbocharger
results in improved horsepower and may help  to reduce emis-
sions due to leaning out of the air-fuel ratio (Ref. 2 and 3)
          Turbochargers are not currently used on OEM spark
ignition engines but are available as retrofit kits for some
after-market applications.   Turbochargers are used on many
OEM diesel engines for improved economy and  power.
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          Failure of the turbocharger results in fuel enrich-
ening due to reduced air intake which will  cause increased
smoke emissions from diesels or HC and CO emissions from
gasoline engines (Ref.  2, 3, 37, 63 and 89).

3.4.5     Superchargers

          Superchargers are belt-driven compressors which
continuously pressurize the intake manifold.   Superchargers
are not available on OEM vehicles and are unusual  for after-
market installations because they represent a continuous
load on the engine and  do not provide significantly better
performance than turbochargers (Ref.  2 and  3).   Superchargers
are, therefore, excluded from the OEM criticality  analysis.
3.5       FUEL INJECTION SYSTEM

          Some spark ignition and all  compression ignition
engines employ fuel  injection systems  which inject fuel  into
either the intake manifold or directly into the cylinder or
its prechamber.  Fuel  injection systems provide more precise
fuel metering than carburetors and, on diesels, are also
needed to overcome the cylinder pressure occurring during
the compression stroke when the fuel  is injected (Ref. 2).
          Fuel injection systems must  fulfill  the following
basic functions:

          •    Meter the correct quantity of fuel for the
               speed and load condition.
          t    Inject the fuel at the  correct  time.
          •    Inject the fuel at the  correct  rate.
          •    Atomize the fuel into  fine droplets.
          •    Distribute the fuel in  the cylinder.
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          The specific design employed to accomplish these
functions depends on the particular engine.   The injection
system may be mechanically or electrically controlled.   In
general, mechanically controlled systems are used in diesel
engines and electrically controlled systems  are used in
gasoline engines (Ref. 2 and 3).

3.5.1     Accumulator  .

          The accumulator is used on the common rail type of
fuel  injection system.  It provides a damping reservoir in a
high  pressure system and does not have a specific failure
mode  (Ref. 3).  The accumulator is not used  on systems  with
return lines to the fuel tank.

3.5.2     Fuel Pump (High Pressure)

          Except for manifold injection of gasoline and the
unit  injector system for diesel engines, all fuel injection
systems utilize high pressure fuel pumps in  the supply  line.
Fuel  pumps are driven directly by the engine using accessory
shafts.  The pumps are positive displacement using either a
gear  pump or plunger and barrel design.  Some pumps incorpo-
rate  speed governors and idle adjustments.  Fuel pumps  are
generally very durable and do not require adjustment or
maintenance within the 50,000-mile service life (Ref. 2 and  3)

3.5.3     Fuel Pressure Sensors/Regulators

          Regulators are used to ensure that the pressure of
the fuel is constant at the injection valves or injectors.
The regulators bypass excess fuel back to the fuel tank or
to the low pressure side of the fuel pump.  Fuel regulators
are usually mechanical, spring-loaded devices.  Pressure
                         3-33

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sensors connected to electronically controlled injection
systems are used on some gasoline injection systems.  Failure
of the pressure regulators will  usually result in higher
than normal fuel pressure which  is analogous to high float
level  in a carburetor (Ref.  2 and 3).

3.5.4      Throttle Linkage and Valve

          Throttling of diesel engines is  performed by
regulating the quantity of fuel  injected.   The gasoline
engine, however, is throttled by regulating the quantity of
fuel and air.   The throttle  linkage and valve is  not emissions
related for gasoline engines.  Throttling  of the  fuel  injec-
tion system is controlled either at the high pressure  pump
or in  the injector.  The throttle linkage  activates rotary
valves which control the quantity of fuel  admitted into the
injectors.  The valves are subject to  wear which  tends to
increase the amount of fuel  injected (Ref. 2 and  3).

3.5.5      Injection Valves

          The  injection valves consist of  spring-loaded
plungers which open when the fuel  pressure exceeds the
spring tension.  The high pressure fuel then flows through
the injector tips into the cylinder (Ref.  2 and 3).
          The  unit injector  system uses a  cam-actuated
plunger and barrel assembly  directly coupled to the injector
tip.  In this  manner, all fuel supply  lines are low pressure.
Each cylinder  has its own crank  adjustment which  throttles
the fuel.  This system -is only used on direct cylinder
diesel injection systems (Ref. 3).
          Injection valves must  be cleaned and adjusted
periodically to ensure that  they are metering the correct
quantity of fuel.  The injectors will  tend to dribble  fuel
if foreign particles become  lodged between the needle  and
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seat.  This results in excess HC,  CO, and smoke emissions
(Ref. 3 and 63) .

3.5.6     Air Sensors/Switches

          Air pressure (vacuum)  or air flow rate sensors are
used on some gasoline electronic injection systems  to help
control the correct air-fuel  ratio.   The sensors provide a
signal which an electronic module  uses to calculate the
required quantity of fuel.  The  pressure sensors are reliable
but are subject to diaphragm deterioration as  in any vacuum
sensing device.  The air flow sensors may stick open
indicating a high air flow rate  incorrectly.   Both  defects
will cause the EFI system to meter excessive  fuel  (Ref. 3,
27 and 58).
          In addition to air flow  sensors, exhaust  oxygen
sensors are also  in use, or planned  for use in conjunction
with future three-way catalyst systems.  The  On sensors
generally have life expectancy similar to spark plugs.
Their failure would usually result in excess  fuel  metering,
although most systems have limited the degree  of enrichment
controlled by the 0~ sensor (Ref.  15 and 62).

3.5.7     Temperature Sensors/Switches

          Sensors of air, water, or  oil temperature are
employed in gasoline injection systems to modulate  the
quantity of fuel  injected.  Some systems also  employ tempera-
ture sensors to regulate air flow  during cold  starts or
under idling conditions.  Temperature sensors  are  generally
reliable and free from wear or deterioration.   Their failure,
however, is analogous to a stuck choke and will cause high
CO and possibly HC emissions (Ref. 3 and 58).
                         3-35

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3.5.8     Fuel Distribution Manifold

          Fuel distribution manifolds consist of the fuel
distribution pipes connecting the fuel  pump to the injectors.
Fuel distribution manifolds may be either high or low pressure
systems.  Fuel distribution manifolds are not subject to
wear or deterioration and are normally  only replaced if
physically damaged.  Therefore, they are not considered in
the OEM criticality analysis.

3.5.9     Injectors (Solenoid)

          Electronic manifold fuel injection systems use
solenoid-activated injectors.  The solenoid is energized by
an electronic distributor which provides the correct timing
of the fuel  flow.  The injector is closed by a return spring
when the solenoid is deactivated.  The  injector contains a
calibrated orifice and needle valve which must be adjusted
for precise  fuel  metering.   The injectors are subject to the
same problems as  described  in paragraph 3.5.5 for mechanically
operated, direct  cylinder injectors.  The characteristic
mode of failure is sticking which will  inject excess fuel to
one or more  cylinders (Ref. 2, 3, 27 and 58).

3.5.10    Triggering Switches

          Electronic fuel injection systems are operated by
distributor  contacts which  control the  timing and sometimes
the duration of the opening of the injector valves.   These
contacts are similar to point contacts  and are timed to
coincide with intake valve  opening.  Trigger contacts are
normally not adjustable;  therefore, little maintenance is
required.  If the distributor shaft wears, however,  the
timing of the injection can become erratic which would
increase emissions of HC  and CO (Ref 3, 27 and 58).
                         3-36

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3.5.11    Electronic Fuel  Injection Control  Circuits

          Electronic fuel  injection systems  use electronic
control  circuits to modulate the frequency and duration of
injector valve opening.   The circuits utilize engine rpm,
manifold vacuum, and air temperature to calculate the actual
airflow, and corresponding fuel  flow required to maintain
the desired air-fuel ratio.   These circuits  are highly
reliable and if they fail, will  disable the  vehicle.  They
are, therefore, excluded from the OEM criticality analysis
(Ref.  2, 3 and 58) .

3.5.12    Starting  Valve

          Both mechanical  and electronic fuel injection
systems  employ starting  valves.   These valves provide addi-
tional fuel during  cold  starts and warm up.   Mechanically-
operated valves provide  additional flow through the cylinder
injection valves.   Electrically-operated injectors  in gasoline
fuel injection systems provide additional  fuel in the
intake manifold.  Failure  of these valves  will result in
excessive CO and HC emissions if they continue to provide
starting mixture enrichment  after the engine is warmed up
(Ref.  3).

3.5.13    Idle Adjustment  Screws

          The minimum flow rate  of fuel through the injectors
is controlled by idling  screws.   Depending on the design,
these  may be located in  the  fuel pump or at  each injector.
The screws require  periodic  adjustment and tend to  increase
flow rate with time.  If not properly adjusted, they may
result in higher emissions,  although the effect is  relatively
small  in comparison to component defects which cause over-
fueling  during cruise operation  (Ref. 2, 3 and 58).
                         3-37

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3.6       ENGINE SYSTEMS

          The mechanical components of the engine can also
affect emissions, particularly as a result of wear and
deterioration leading to misalignment.  The engine system
components which are emissions-related include the following:

          •    Exhaust valves and valve components such as
               lifters, cams, guides, and  seals.
          •    Piston rings.
          •    Piston including piston, rod,  head, and
               cylinder wal1 .
          t    Head gaskets.
          •    Camshafts.

3.6.1     Exhaust Valve Components

          The exhaust valves  seal the combustion  chamber to
prevent escape of hot combustion products  until  after the
expansion stroke of the piston.  The exhaust  valves  can
become burned, misaligned, worn, or stuck, in which  case
unburned combustion products  would be released.   The com-
ponents which affect the closing and sealing  of  the  exhaust
valves are discussed below.

3.6.1.1   Lifters and Springs

          The valves are opened by push rods  and  lifters, and
closed by springs.   Changes  in the physical dimensions or
mechanical properties of either lifters or springs will
result in changes in valve timing.  Valve  timing  has a
strong relationship to performance and emissions  because the
valves may open or close at  the wrong time (Ref.  3).
          The valve lifter transmits the action  of the cam
to the valve.  Lifters may be directly connected  to  the
                         3-38

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valve stem or may act on push rods  which,  in  turn,  act to
open the valve.   The lifters  may be either simple  mechanical
rods or the more complex hydraulic  lifters.   Mechanical
lifters must be  adjusted so that the correct  gap (lash)  in  a
cold engine exists between the valve stem  and valve lifter.
The gap allows for thermal expansion of the  valve.   Hydraulic
lifters are used on most engines to avoid  valve  lash adjust-
ments and to provide quieter  lifter operation (Ref. 3).

3.6.1.2   Cams

          The cam lifts the valve at the correct time to
obtain the most  efficient filling and emptying of  the cylin-
der.  The operation of the valves is controlled  by  precision-
machined cams.  The cams are  hardened to minimize  wear.
However, over a  long period of operation,  or  in  the case  of
improper operation or fabrication,  the shape  of  the cam  will
change.  Wear usually occurs  on the highest  point  of the  cam
decreasing the lift of the valve.  This results  in  a smaller
opening and reduced breathing of the engine.   This  does  not
significantly effect emissions, but does reduce  engine
power.  Wear can also occur on the  sides of.the  cam, parti-
cularly with strong springs or hydraulic lifters.   In this
case, the valve  timing will change  which can  affect emissions
(Ref. 3).
3.6.1.3   Guides

          Valve guides are pressed into the head of the
block and serve to correctly align the valve with its  seat
in the cylinder.  Similar guides are provided for push rods
if they are used.   The guides are lubricated by oil running
down the valve stem.   As the guides and valve stem wear,
more oil can flow  down the stem and into the manifold  or
                          3-39

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into the cylinder.   This can increase smoke and HC/CO
emissions (Ref. 3).

3.6.1.4   Seals

          Seals are  installed to prevent leakage of lubri-
cating oil  past the  valve guides and into the manifold or
cylinder.  The seals are subject to wear and deterioration
and will cause increased CO and smoke emissions if defective
due to incomplete combustion of the heavy lubricating oil
(Ref.  3).

3.6.1.5   Valves

          Intake valves are not subject to the wear and
deterioration typical  of exhaust valves because they operate
at low temperatures.  Exhaust valves, however, are subject
to high temperature, vibration, and impact stress.  The
valve  and its seat  in  the cylinder must make a tight seal at
the correct time to  ensure that the combustion in the cylinder
can be utilized efficiently without excessive emissions.
Valve  leaks can be  caused by improper alignment of the valve
train, by erosion or wear of the valve and seat, or by
deposits which prevent a positive seal.  Under these condi-
tions, exhaust gases will escape from the cylinder before
combustion  is complete causing generally higher HC, CO, and
smoke, but  lower NO   emissions (Ref. 3).
                   /\

3.6.2      Piston Rings

          Piston rings consist of oil control rings and
compression rings.   The oil control ring is the lowest on
the piston  and is designed to minimize movement of oil from
the crankcase into  the cylinder where it would burn, resulting
in excessive CO, HC, and smoke emissions.  The compression
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rings (two or more)  are located near the top of the piston
and are designed to  seal  the combustion gases in the cylinder.
Leakage past the compression rings  is called blowby which
occurs during the compression stroke and initial phase of
the expansion stroke.   Blowby is captured by the PCV system
and returned to the  intake manifold for subsequent combustion.
Excessive blowby has the  effect of  enrichening the mixture
particularly at idle and, therefore, increasing CO emissions
(Ref. 2 and 3).

3.6.3     Pistons

          The piston is related to  emissions because the
design of the piston surface is peculiar to the specific
engine design.  Some pistons are manufactured with special
depressions to permit localization  of the flame front.  The
surface is subject to pitting or deposits which affect the
ignition and quenching properties of the combustion chamber.
As OEM parts, the pistons are not significantly related to
emissions because the rate of wear  and deposition is so
small during the design life (Ref.  3).  As after-market
components, however, there is a possibility of changing
cylinder geometry by using nonstandard replacement pistons.
This may affect HC and NO  emissions due to changes in
                         A
compression ratio and surface to volume ratios (Ref. 2).

3.6.4     Gaskets

          Gaskets are used to provide positive seals between
the sections of the  engine.  Defective engine gaskets create
water or oil leaks inside the engine block which affect the
combustion process (Ref.  3).  Gaskets should not fail during
the certification period  unless the engine has been improperly
fabricated or operated.
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3.6.5     Camshafts

          Camshafts and their drive mechanisims are emissions
related because of their effect on valve operation.  Defects
are generally associated with the belt or chain drive mechan-
ism of overhead camshafts.   This wear causes valve timing to
change or become erratic.   However, these problems develop
over long periods of operation and should not affect emis-
sions during the certification period (Ref.  3).
3.7       EMISSION CONTROL SYSTEMS

          A large number of systems  and  components  have been
developed by engine and vehicle manufacturers  specifically
to control  emissions.   Defects  in  these  systems  will  usually
result in increased emissions of at  least one  pollutant.
Some systems are used  on most engines.   Others  maybe  used  on
only a few engines of  a single  manufacturer.   Separate
paragraphs are devoted to the following  systems:

          •    Crankcase ventilation (PCV)
          t    Evaporative emissions (EVAP)
          •    Air injection (AIR)
          •    Exhaust gas recirculation (EGR)
          •    Transmission-controlled  spark  (TCS)
          •    Speed-controlled spark  (SCS)
          t    Orifice spark advance control  (OSAC)
          t    Electronic spark control  (ESC)
          t    Catalytic reactor (CAT)

          In addition, several  individual components  have
been developed and are discussed separately  under Miscellan-
eous Emissions-Related Parts:

          •    Heat riser
          •    Electric assist  choke
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          •    Staged choke pulldown
          •    Decel  valve
          f .   Distributor vacuum deceleration valve
          •  .  Thermal  vacuum valves
          •    Distributor starting solenoid

3.7.1     Positive Crankcase Ventilation (PCV) Systems

          The first emission control system used on vehicles
was the positive crankcase ventilation system.  The PCV
system provides a controlled flow of fresh  air through the
engine crankcase.  The  closed type of PCV system, used on
1968 and later vehicles prevents escape of  blowby gases into
the atmosphere.  Individual system designs  vary by manufac-
turer but generally include the following components:

          •    PCV valve
          •    PCV hoses
          «    PCV fresh air filter  .
          •    PCV oil  separator

3.7.1.1   PCV Valve

          The purpose of the PCV valve is to reduce the flow
through the system during idle and deceleration when manifold
vacuum is high.  Without the PCV valve, the flow through the
PCV system would be very high due to the vacuum.  At the
same time, the carburetor airflow is low.  The extra airflow
through the PCV system  would cause lean misfire and possibly
stalling of the engine  (Ref. 3).
          The PCV valve is a spring-loaded  plunger which is
open at low vacuum; i.e., open throttle.  This enables
relatively high flow rate through the valve during times of
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high speed operation.   Under high vacuum, the valve is
closed against the spring leaving small  orifices for the
gases to flow through.   This maintains PCV flow in proportion
to the low carburetor  airflow in spite of the high manifold
vacuum.   Flow through  the PCV valve can  be restricted by
clogging from particles and oil  droplets drawn out of the
engine crankcase.  This results  in some  fuel  enrichment and
increased HC and CO emissions because less air is drawn into
the engine and can result in backflowing of crankcase gases,
under pressure, to the  air cleaner (Ref. 3 and 27).  This
can also result in flow restriction of the air cleaner.

3.7.1.2    PCV System Hoses

          The PCV valve is connected to  the manifold vacuum
port by  reinforced rubber vacuum hoses.   Similar hoses
connect  the air cleaner to the crankcase air  inlet which may
be in the oil filler cap or the  valve covers.  The PCV
system may also be interconnected with the EGR or EVAP
systems  (Ref. 3).
          Breaks or loose connections in the  PCV hoses can
result in loss of blowby fumes,  primarily unburned fuel,
into the atmosphere.  They may also create a  manifold vacuum
leak if  the break occurs in the  hose connecting the manifold
to the PCV valve.

3.7.1.3    PCV Fresh Air Filter

          An auxiliary  filter is usually supplied to filter
airborne particulates  from the crankcase ventilation air.
Clogging of the filter  will reduce ventilation flow.  If oil
is clogging the filter, it may indicate  that  the PCV valve
is also  clogged.  Reduced flow through the filter will
result in enrichening  of the air-fuel ratio and higher CO
emi ssions (Ref. 3).
                          3-44

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3.7.1.4   PCV Oil  Separator

          An oil  separator is  supplied  with  some engines to
help remove entrained oil  droplets  from the  crankcase
vapors.  However,  most of  these are integral  parts of the
engine block or valve covers  and cannot be serviced.   Failure
of an oil  separator results in more oil passing through the
PCV system which  encourages early failures due to clogging
(Ref. 3).

3.7.2     Evaporative Emission Control  (EVAP)  System

          Evaporative emission control  systems prevent
escape of  gasoline vapors  from the  fuel tank  and carburetor.
All manufacturers  use similar  systems,  although the specific
components and flowpaths  may  differ.   The EVAP system generally
consists of the following  components:

          •    Activated  carbon canister
          •    Vacuum, vapor,  and gasoline hoses and  line
          •    Fresh air  filter
          •    Vapor-liquid separator
          t    Vapor control  valves

3.7.2.1   Activated Carbon Canister

          Most systems employ  an activated carbon canister
to store the fuel  vapors.   During engine shutdown, the fuel
vapors are routed  to the  activated  carbon canister by the
slight pressure of the expanding vapors.  The  activated
carbon in  the canister absorbs and  holds the  vapors allowing
vapor-free air to  escape  to the atmosphere.   When the engine
is started, manifold vacuum draws the  absorbed vapors into
the engine.  The  carbon canister is very durable even if
occasionally saturated.  Failure of the canister causes
excessive  evaporative HC  emissions  (Ref. 3 and 27).
                         3-45

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3.7.2.2   EVAP System Hoses and Lines

          The evaporative system involves several  vapor,
vacuum, and liquid lines, and their associated connectors
and fittings.  A break in any line will  release fuel  vapor
to the atmosphere.  In addition, a break in the vacuum line
between the carburetor and canister may  cause lean misfire
due to the vacuum leak.

3.7.2.3   EVAP System Fresh Air Filter

          The canister incorporates a filter for removal of
large particulates and droplets from the purge air.   This
prevents clogging of the carbon which could reduce its
efficiency for storage and purging.  A restricted  EVAP
system filter may increase evaporative HC emissions  because
the canister is not effectively purged between soaks  (Ref. 3
and 27).

3.7.2.4   EVAP Vapor/Liquid Separator

          The liquid fuel is separated from the fuel  vapor
in or immediately adjacent to the fuel tank by a separator
which directs the fuel vapors to the canister.  The  separa-
tor is usually of a simple standpipe design and, therefore,
is durable and reliable.  To prevent overfilling of  the  fuel
fuel  tank and, consequently, flooding of the separator,  an
expansion void is frequently incorporated in the fuel  tank
(Ref. 27).

3.7.2.5   EVAP Vapor Control Valves

          Several vapor control valves may be used in  the
EVAP system.  These include check valves and vacuum  valves
which regulate the direction and flow rate of fuel vapors
                          3-46

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into and out of the canister.   These valves  are frequently
an integral  part of the activated carbon canister or fuel
tank.   However, where the valve is a separate replaceable
component, it is included in this category.   The vacuum
valves control  the purge air flow rate in the same manner  as
the PCV valve regulates crankcase ventilation air.  At idle,
low flow is  allowed through small orifices.   However,  at
higher speeds when higher flows from the EVAP system can be
tolerated, the  purge valve opens under spring action allowing
flow through larger orifices (Ref. 27).

3.7.2.6   Fuel  Tank

          The fuel tanks are integral  parts  of the EVAP
system and may  include vapor separators, fuel return lines,
and expansion chambers.  The fuel tanks  also incorporate a
sealed gas cap  which permits make-up air to  enter the  tank
but prevents fuel vapors from escaping except to release
dangerously  high pressure.  Failure of the gas cap will
release fuel vapors to the atmosphere  (Ref.  3 and 27).

3.7.3     Air Injection (AI) System

          Air injection systems have been used for emissions
control since 1966 with only slight modification.  Air
injection systems use auxiliary air injection adjacent to
the exhaust  valves to oxidize HC and CO  emissions leaving
the cylinder.  Air injection systems are effective in  reduc-
ing emissions because of incomplete combustion in the  quench
zones, scavenging of unburned carbureted mixture during
intake and exhaust valve overlap, and  excess emissions due
to carburetor or ignition system defects.  Some catalyst-
equipped vehicles utilize air injection  at the catalyst
rather than  in  the exhaust manifold.  The details of the
systems vary somewhat, although similar  components are
generally used.
                         3-47

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          Air injection systems consist of the following
components :

          t     Distribution manifold and nozzles
          •     Hoses
          •     Inlet air filter
          t     Check valves
          f     Bypass or diverter valves
          t     Gulp valves
          •     Pump, belt,  and seals

3.7.3.1   Manifold and Nozzles

          The manifold and  nozzles  are  fabricated  in  or on
the engine.   They should be good  for the life  of the  engine
and there is no significant emissions  failure  mode  (Ref.  3).

3.7.3.2   Hoses

          Reinforced vacuum hoses are  used to  connect the
air.injection pump to the air distribution manifold.   The
hoses are subject to thermal  and  mechanical  deterioration.
However, unless completely  broken,  there should  not  be a
significant  reduction in air  delivery.   The  air  injection
hoses should not fail within  the  certification period, but
if they do,  will  result in  no air delivery (Ref.  3  and 27).

3.7.3.3   Inlet Filter

          A  particulate filter is installed  in the  intake to
the pump.  This filter prevents the introduction of  coarse
particulates into the pump  which  could  damage  the  pump and
clog  air control  valves or  injector tips.   The air  filter is
usually integral  to the pump  and  is designed to  last  the
life  of the  pump under normal use (Ref.  3).
                         3-48

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3.7.3.4   Check Valves

          All  AI systems employ check valves to prevent
backflow of hot exhaust gases in the event of high pressure
in the exhaust manifold or failure of the air pump or hoses.
The check valves are generally good for the life of the
engine and help prevent damage to the pump or hoses if
backfiring or  detonation occurs in the manifold (Ref. 3).

3.7.3.5   Bypass or Diverter Valves

          Several  different types of bypass or diverter
valves are used to prevent backfiring, and in catalyst-
equipped vehicles, excessive temperature due to certain
engine operating conditions.  The bypass or diverter valves
dump air into  the atmosphere during deceleration (high
vacuum) and high speed (high air supply pressure).  The
valves are generally operated by manifold vacuum.   Catalyst-
equipped vehicles may also have thermally controlled switches
which activate the diverter valve to prevent high  temperatures
in the catalyst during deceleration, cold start, or engine
malfunction.  The diverter valve is subject to diaphragm
deterioration  which can prevent the valves from operating
during deceleration (Ref. 3 and 27).

3.7.3.6   Gulp Valves

          Gulp valves were incorporated on early air injection
systems but generally have been eliminated in favor of the
diverter or bypass values presently used.  Some foreign
manufacturers  use a form of gulp valve for control of
deceleration hydrocarbon emissions.  These valves  admit
additional air to the carburetor or intake manifold to
prevent excessive fuel enrichment during deceleration.  Gulp
and mixture control valves are used to regulate airflow
                         3-49

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into the intake manifold.   Throttle-poppet valves regulate
airflow past the throttle.  All  three valve types are
spring-controlled vacuum valves  which open under conditions
of high manifold vacuum.  Failure of the valve will  result
in mixture enrichment during decelerations and higher HC and
CO emissions (Ref. 3 and 27).

3.7.3.7   Pump, Belts and  Seals

          The air injection pump and associated belts,
pulleys, and seals provide the air supply for the AI  system.
The pump is highly reliable and  should operate well  beyond
the certification period.   However,  improper belt tension
adjustment can cause slippage  or excessive wear of the belt.
Excessive tension can also cause accelerated wear of  the
pump pulley bearings.  Pumps are generally not serviceable
and are replaced when defective.  If defective, the  AI
system will be disabled causing  higher HC and CO emissions
(Ref. 3 and 27).

3.7.4     Exhaust Gas Recirculation  (EGR) Systems

          Control of NO  emissions is partly accomplished by
                       rt                                  •
EGR, in which a portion of the inert exhaust gases are metered
back into the intake manifold.  The  exhaust gases reduce
combustion temperatures and prevent  formation of NO  .   Two
                                                   J\
EGR concepts have been employed:  passive bleed jets  between
the exhaust and intake manifolds; and actively modulated EGR
valves modulated by temperature, vacuum and/or exhaust
pressure.  As emission standards have become more stringent,
the complexity of EGR systems  have increased.  EGR systems
can be composed of the following components:

          •    EGR valve or orifice
          •    Hoses
                         3-50

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          t    Temperature-controlled vacuum valves
          §    Solenoid-controlled vacuum valves
          •    Temperature switch
          •    Speed/transmission switch
          •    Time delay control
          •    Vacuum amplifier
          •    Vacuum-reducing valve
          •    Carburetor spacer
          •    Back pressure sensor
          •    Check valves

3.7.4.1   EGR Valve or Orifice

          The fixed orifice or floor jet type EGR valve was
used only in a few engine families.  Therefore,  these systems
will not be discussed other than to say that plugging of the
orifices was common.  The vacuum-modulated EGR valve, now
used exclusively, consists of a vacuum, diaphragm-operated
valve.  Vacuum signals, modulated by load and sometimes
thermal conditions, are used to open the valve in proportion
to throttle opening.  The valve is closed by return springs.
The EGR valve is subject to thermal and mechanical  deteriora-
tion and clogging by particulates, condensed water, and oil
in the exhaust gases.  Failure of the EGR valve  increases
NOV significantly (Ref. 2, 3, 27 and 86).
  A

3.7.4.2   EGR Hoses, Passages, Seals

          Except for some after-market retrofit  systems, all
hoses or tubes carrying the exhaust gases are metalic to
resist the high exhaust gas temperature.  EGR vacuum control
lines, however, are standard vacuum-hoses.  Failure of
vacuum hoses or fittings can result in a vacuum  leak as well
                          3-51

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as disabling the EGR system.  This will  increase both HC and
NO  emissions (Ref.  3 and 27).
  n

3.7.4.3   EGR Temperature-Control 1ed Valves
          Thermal  vacuum valves are used in some applications
to modulate EGR during cold temperature operation.  These
valves usually sense coolant temperature and shutoff vacuum
signals activating EGR.   This promotes more rapid warm up
for control of cold start HC and CO emissions.   Failure of
the valve to open  would  increase NO  substantially.   Failure
                                   /\
of the valve to close would slightly increase HC and CO
during warm up (Ref. 3 and 27).

3.7.4.4   EGR Solenoid-Controlled Vacuum Valves

          Some systems are modulated by electrically-operated
solenoid valves which may be interconnected with TCS, SCS,
or thermal  vacuum  switch systems.  The solenoid vacuum
valves are  generally more reliable than vacuum-operated
valves.  The characteristic failure will prevent opening of
the valve which prevents any EGR (Ref. 3 and 27).

3.7.4.5   EGR Temperature Switches

          Temperature switches are used in conjunction with
solenoid-controlled vacuum valves to regulate EGR during
cold temperature operation.  Temperature-sensing switches
are very reliable  and should not require servicing.   Their
failure will prevent any EGR (Ref. 3 and 27).

3.7.4.6   EGR Speed/Transmission Switch

          Some systems modulate EGR in conjunction with
transmission gear  position or speed.  These systems  are
                          3-52

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often interconnected with timing retard systems.  These
switches are very reliable and should not require servicing.
Their failure will  prevent EGR at any speed (Ref. 3 and 27).

3.7.4.7   EGR Time  Delay

          Some applications use electrical delays to prevent
EGR immediately following start-up to ensure stable idling
These systems employ electrical timers which activate a
vacuum solenoid valve to prevent EGR even though the coolant
temperature is high enough to permit EGR.  Failure of the
time delay mechanism may prevent any EGR (Ref.  3 and 27).
Since this is a more severe failure condition than providing
EGR at all times, it has been selected as the mode of failure
for this study.

3.7.4.8   EGR Vacuum Amplifier

          Some systems employ a ported vacuum signal to
control EGR in proportion to the throttle opening.  The
ported vacuum signal, however, may not be strong enough to
actuate the EGR valve.  Therefore, manifold vacuum is used
to operate the valve and is modulated by the ported vacuum
in a manner similar to electric relays.  The EGR vacuum
amplifier will create a large vacuum leak if defective.
This can affect performance and increase both HC (misfire)
and N0y (no EGR) (Ref. 2, 3 and 27).
      /\

3.7.4.9   EGR Vacuum-Reducing Valve

          Some applications use a vacuum-reducing valve to
reduce the manifold vacuum under certain conditions.  This
valve consists of, or is used in conjunction with, a solenoid
or thermal vacuum valve which opens an air bleed to release
or reduce the vacuum signal.  Vacuum-reducing valves are
used to modulate EGR under certain throttle or temperature
conditions (Ref. 3 and 27).
                          3-53

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3.7.4.10  EGR Carburetor Spacer

          The carburetor spacer contains passages for
introducing the recirculated exhaust gases into the carbureted
mixture.  The spacer is not subject to significant deteriora-
tion, but the passages can become clogged with exhaust
gas particles.  The failure of the spacer would increase NO
                                                           A
because EGR flow would be reduced (Ref.  3 and 27).

3.7.4.11  EGR Back Pressure Sensor

          Some California-configuration  vehicles employ a
back pressure sensor to more accurately  proportion the EGR
to load and throttle opening.   The back  pressure sensor
responds to pressure in the exhaust manifold which increases
with throttle opening.  The pressure moves a diaphragm
against a spring to close an air bleed in the vacuum line of
the EGR valve.  Thisincreases the vacuum signal and results
in higher EGR.  This valve can become clogged resulting in
reduced EGR at all times and,  consequently, higher NO  (Ref. 3
and 27).

3.7.4.12  EGR Check Valves

          Some applications use a check  valve to hold the
highest ported vacuum obtained during acceleration to ensure
high EGR and reduced NO .  These valves  are reliable and not
                       A
subject to severe operating conditions.   Therefore, they
should operate satisfactorily  well beyond the certification
period.  Their failure will result in normal vacuum variations
and slight reduction in EGR (Ref. 3 and  27).

3.7.5     Transmission-Controlled Spark  (TCS)

          Most manufacturers use transmission-controlled
spark systems to reduce timing advance during certain operating
                         3-54

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conditions.   Acceleration and heavy load operation are
typically performed in low gears.   Therefore, TCS systems
are designed to provide retarded timing except in the highest
gear.   Both  manual  and automatic transmissions may use speed
sensors instead of  transmission gear sensors.  TCS systems
incorporate  numerous protective and override systems and are
frequently interconnected with EGR systems.
          TCS systems consist of the various combinations of
the following components:

          •     Solenoid vacuum valve
          •     Vacuum lines and hoses
          t     Time delay control
          •     CEC  valves
          •     Thermal vacuum valves
          •     Transmission switch
          •     Reversing relay

3.7.5.1   TCS Solenoid Vacuum Valve

          An electrically-operated solenoid  valve controls
the amount of vacuum provided to the distributor vacuum
advance diaphragm.   In some configurations,  the valve selects
either ported or manifold vacuum sources.  In others, it
provides full manifold vacuum or vents vacuum to the atmos-
phere which  provides no vacuum advance at all.  Depending on
the configuration,  the valve could fail providing either no
or full advance at  all times.  For NO  , full advance at all
                                     /\
times is the most critical failure mode (Ref. 3 and 27).

3.7.5.2   Vacuum Lines and Hoses

          The distributor advance unit is connected to the
manifold vacuum by  a very complex routing of vacuum lines.
Any leak in  the lines will result in reduced vacuum advance
                         3-55

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which will reduce NO  and may create vacuum leaks resulting
                    /\
in higher HC emissions due to lean misfire (Ref. 3 and 27).

3.7.5.3   TCS Time Delay Control

          Some systems incorporate time delays to permit
stable idling before the TCS system is activated.  They
operate in the same manner described above for EGR time
delay controls and will prevent TCS operation if defective
(Ref. 3 and 27).

3.7.5.4   TCS CEC Solenoid

          Some vehicles use a CEC solenoid in the TCS
system.  The CEC solenoid incorporates the functions of a
throttle positioner and a vacuum solenoid.  The CEC solenoid
simultaneously regulates distributor vacuum advance and
throttle closure.  The CEC plunger must be properly adjusted
to correctly regulate deceleration from high speed to prevent
excess HC emissions.  Once adjusted, however, the valve and
plunger should not require service during the certification
period.  Failure of the CEC solenoid will result in no
deceleration throttle control and no vacuum advance.  This
will cause reduced NO  but higher HC and CO (Ref. 3 and 27).
                     /\

3.7.5.5   TCS Thermal Vacuum Valve

          The TCS system may be modulated by several thermal
vacuum valves which sense coolant temperature.  The vacuum
valves are usually used to disable TCS vacuum retard when
the coolant temperature is less than or greater than specified
limits.  Thermal  vacuum valves  (TVV) are also called ported
vacuum switches  (PVS), coolant  temperatures overrides (CTO)
and thermal ignition control (TIC) valves.  Thermal vacuum
valves come in numerous configurations such as two, three,
four and five port valves and various temperature ranges
                         3-56

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(Ref.  3 and 27).   Thermal  vacuum valves are durable and not
exposed to severe environments.  They should, therefore,
operate beyond the certification period.  If they fail, they
will most likely  fail in the normal operating position
providing normal  vacuum advance.

3.7.5.6   TCS Transmission Switch

          The TCS solenoid vacuum valve is actuated by a
transmission switch which  senses gear selection.  It is
identical in nature and operation to the EGR transmission
switch described  above (Ref. 3 and 27).

3.7.5.7   TCS Reversing Relay

          A relay is provided in a few applications which
defeats the vacuum retard  function of the TCS system.   One
configuration employs a latching relay which prevents  TCS as
long as carburetor inlet air temperature is low.  Once the
air temperature becomes higher, the TCS function is restored
This system could prevent  any vacuum retard, if defective,
resulting in increased NO   emissions (Ref. 3 and 27).
                         /\

3.7.5.8   TCS Temperature-Controlled Switch

          In some applications, the temperature override
function of the thermal vacuum valve is performed by an
electrical switch wired in series between the speed switch
and solenoid vacuum valve.  This switch functions in the
same manner as described for EGR temperature-controlled
switches (Ref. 3  and 27).

3.7.6     Speed-Controlled Spark (SCS) System

          Some applications utilize speed-controlled spark,
particularly on automatic  transmission vehicles.  The SCS
                          3-57

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system is distinguished from TCS primarily because road
speed is sensed in terms of mph rather than transmission
gear selection.  The other components are similar and, in
many cases, identical  to TCS systems and will  not be discussed
further (Ref.  3 and 27).

3.7.7     Orifice Spark Advance Control  (OSAC)

          The  orifice  spark control  system is  a method of
modulating vacuum advance.  The system is used in conjunction
with EGR or TCS for control of NO .   The system incorporates
                                 A                •
override systems during certain engine operating conditions.
The OSAC system incorporates the following components:

          t    OSAC orifice valve
          •    OSAC vacuum hoses
          •    OSAC vacuum control  valves
          •    OSAC temperature sensor

3.7.7. 1   OSAC Orifice Valve

          The  OSAC orifice valve is  similar in function to
the spark delay valve.  The valve delays increase of ported
vacuum to the  distributor vacuum advance unit  as the throttle
is opened.  During throttle closure, the reduction of ported
vacuum is instantaneous.  This effectively retards timing
during loaded  accelerations.  The OSAC valve consists of an
integral orifice and check valve which restricts flow in one
direction but  not the  other.  The OSAC valve is typically
located on the air cleaner housing where it senses air
temperature in the air cleaner.  Failure of the valve enables
normal vacuum  signals  to reach the distributor and increase
NOY (Ref. 3 and 27).
  n
                         3-58

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3.7.7.2   OSAC Vacuum Hoses

          Vacuum hoses are routed between the OSAC valve,
the distributor vacuum advance unit and the thermal  control
valves.  The hoses must be leak tight to ensure correct
operation of the OSAC system.   Vacuum hose failure between
the OSAC valve and thermal vacuum valve will  result  in no
vacuum advance unless overheating occurs; then full  vacuum
advance.  Vacuum hose failure  between the manifold vacuum
source and distributor vacuum  advance unit may result in no
vacuum advance and/or intake manifold vacuum leak depending
on temperature.  Emissions of  NO  and possibly HC will
                                A
increase (Ref. 3).

3.7.7.3   OSAC Vacuum Control  Valve

          The OSAC vacuum control valve, also called the
thermal ignition control  (TIC) or temperature operated
bypass (TOB) valve, is used on some vehicles to apply full
manifold vacuum to the distributor advance unit if the
engine overheats.  This valve  is termed a coolant temperature
override valve or thermal vacuum valve by other manufacturers
when associated with distributor vacuum advance modulation.
The higher manifold vacuum causes higher engine rpm  and
improved cooling.  The valve is located in the cooling
jacket or the radiator, depending on application.  Failure
of the valve either provides delayed ported or full  vacuum
advance at all times (Ref. 3 and 27).

3.7.7.4   OSAC Temperature Sensor

          Some OSAC systems were modulated by air temperature
using a temperature sensor integral to the OSAC orifice
valve body.  This sensor defeats the OSAC valve during cold
ambient temperatures to improve driveabi1ity .  The temperature
                          3-59

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sensor bypasses the ported vacuum around the orifice in the
OSAC valve (Ref.  3 and 27).

3.7.8     Electronic Spark Control  (ESC) System

          The electronic spark control  system was used in
some applications to modulate vacuum advance during various
operating conditions.  The system regulated vacuum advance
using electrical  sensors and solenoids  rather than thermal
vacuum valves.  The ESC system is not related to electronic
ignition systems.  The ESC system is composed of the following
components :

          t     Electronic module
          t     Vacuum hoses/wires
          t     Solenoid vacuum valves
          •  .   Temperature-sensing  switches
          •     Speed-sensing switches

3.7.8.1   Electronic Module

          The distributor vacuum is modulated by a solenoid
which is controlled by the electronic module.  The electronic
module compares ambient temperature and vehicle speed to
specified values.  Above 65°F, the  module will  disable the
vacuum advance at low speed  and enable  it at high speed
(23 to 35 mph depending on application).  Below 49°F, the
module will  enable vacuum advance at all speeds.  The module
consists of  solid-state circuits and is highly reliable.
Failure of the module will result in normal vacuum advance
at all times (Ref. 3 and 27).

3.7.8.2   ESC Hoses

          The solenoid vacuum valve is  placed between the
manifold vacuum source and distributor  advance unit.
                         3-60

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Failure of the hoses will  result in loss of advance to the
distributor and may create a vacuum leak causing high HC
(Ref. 27).

3.7.8.3   ESC Solenoid Vacuum Valve

          The ESC solenoid vacuum valve, also called a
distributor modulator valve (DMV), controls the vacuum to
the distributor.  Failure  of the solenoid will  result in
normal  vacuum advance at all times and higher NO  emissions
(Ref. 27).

3.7.8.4   ESC Temperature-Sensing Switch

          The ambient air  switch overrides the  speed modula-
tion of the distributor.  Failure of the switch disables the
ESC system resulting in normal  operation of the ESC «>ystora-
(Ref. 27)

3.7.8.5   ESC Speed-Sensing Switch

          The speed sensor is driven by the speedometer
cable..  It is a DC tachometer generator and is  highly
reliable.   Failure of the  sensor would result in no vacuum
advance at anytime.  This  reduces NO  but also  can increase
                                    A
emissions  HC and CO slightly (Ref. 27).

3.7.9     Catalytic Reactor

          Most 1975 and 1976 model-year vehicles are equipped
with catalytic reactors for control of HC and CO emissions
and to permit some reduction of NO  emissions by enrichment
                                  A
of carburetor adjustments.  Catalysts consist of the follow-
ing components:

          •    Reactor body
          •    Active media
                          3-61

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          In addition to the catalyst itself,  some systems
employ catalyst protection devices  which  modulate air injec-
tion.   The air injection systems  were discussed in
paragraph 3.7.3.

3.7.9.1   Reactor Body

          The outer catalyst body consists  of  heat shields
to protect the underside of the vehicle  from fire.  The
catalyst shell itself is heat resistent  stainless steel  and
incorporates flow diffusers to direct and distribute the
exhaust gas throughout the catalyst.   The structural  body is
not subject to deterioration but  can  be  damaged by collision
or impact.  Failure of the catalyst body  will  increase  HC
and CO emissions  slightly (Ref. 27, 35,  47,  59, 72,  81  and 82)

3.7.9.2   CAT Active Media

          Catalytic active media  is usually  platinum but may
also include some palladium and rhodium.   The  active media
is subject to deterioration by chemical  bonding with poisons
such as lead and  phosphorus.  The active  media may also be
damaged by physical coating by particulate  material  (Ref. 72
73, 76, 81 and 82).
          Catalysts are either monolithic or pelleted.   In
both cases, the active media is distributed  over and supported
by an  inert silicate which provides large surface area.
Thermal cycling and stress tends  to cause the  pore size to
increase reducing the surface area.  This helps to explain
the gradual loss  of catalyst efficiency  typical of high
mileage accumulation.  Without ignition  or  carburetion
                         3-62

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failure, the catalyst should last the design  life of the
vehicle.  However, structural  damage to the catalyst,  due to
high temperature, results  in substantial  increases in  both
HC and CO emissions (Ref.  7, 10,  15, 28,  29,  35,  47, 72, 73,
81 and 82).
          Several catalytic systems, including dual  catalysts
and three-way catalysts,  are under active development  and pre
certification testing.   These  catalyst systems have  not
been included in this study.  They are expected to have
similar relationships to  emissions as conventional oxidation
catalysts.

3.7.10    Miscellaneous Emissions-Related Parts

          Several components are  not specifically included
in any emissions control  system.   These parts  include:

          •     Heatriser
          •     Electric assist choke
          0     Staged choke pulldown
          t     Decel  valve
          t     Distributor deceleration valve
          •     Thermal  vacuum  valve
          •     Distributor vacuum valve

3.7.10.1  Heat Riser

          The heat riser,  also called manifold heat  control,
has been employed on  most  engines for many years  to  improve
cold start  performance  and emissions and  to reduce warm-up
time.  The  heat riser is  a thermostatically-controlled  valve
which directs exhaust gases against the intake manifold  when
the engine  is cold.  When  the  engine is hot,  the  valve
closes to direct the  exhaust gases into the exhaust  pipe.
The heat riser can stick,  typically closed, so that  warm-up
                         3-63

-------
is delayed causing increased HC and CO emissions.   Some
engines use vacuum-operated valves (Early Fuel  Evaporation,
Exhaust Heat Control) modulated by thermal  vacuum switches,
to activate the heat riser (Ref. 2, 3, 48 and 78).

3.7.10.2  Electric Assist Choke

          Some engines use electric resistance  heaters to
cause more rapid choke opening.  The choke  thermostat operates
normally.  At low ambient temperatures, the heater  is deacti-
vated by a bimetal thermostat.   At higher ambient  temperatures
(60°F), the heater is activated providing additional  heat to
the choke thermostat.  The more rapid choke opening reduces
HC and CO emissions.  Failure of the system would  cause
higher HC and CO cold start emissions (Ref. 3 and  27).

3.7.10.3  Staged Choke Pulldown

          The staged choke pulldown used on some models
provides more accurate choke modulation as  a function of
temperature.  The pulldown consists of a temperature-controlled
vacuum valve which pulls the choke open more rapidly  than
normal.  The rate of opening is controlled  by fluid flowing
through an orifice.  This permits a vacuum  diaphragm  connected
to the choke plate to move.  At temperatures above  60°F, the
temperature valve opens allowing vacuum to  pull  the choke
nearly open soon after engine start.  At colder  temperatures,
normal choke opening is provided.  Failure  of the  valve will
usually result in normal choke  action and slightly  higher CO
and HC emissions (Ref. 3 and 27).

3.7.10.4  Decel Valve

          The decel valve is used to provides additional
carbureted mixture during periods of high intake manifold
                          3-64

-------
vacuum, (i.e., decelerations).   The valve is a  diaphragm
which opens under vacuum to admit a mixture of  fuel  and air
to the intake manifold.   The added fuel  maintains stable
combustion and engine operation, thereby, reducing HC and CO
emissions.  Defects in the valve will  usually cause  increased
emissions either due to  insufficient or  excessive additional
mixture (Ref. 2, 3 and 27).

3.7.10.5  Distributor Vacuum Deceleration Valve

          The distributor vacuum deceleration valve  (DVDV)
also called deceleration or vacuum advance control valve is
used to provide maximum  vacuum  advance of ignition timing
during deceleration thigh manifold vacuum).  At idle and
normal part throttle operation  (low vacuum), the distributor
advance is connected to  the carburetor spark port for normal
advance modulation.  The DVDV consists of a spring-loaded
vacuum diaphragm which responds to manifold vacuum to control
the vacuum source provided to the distributor.   Failure of
the valve diaphragm will result in manifold vacuum applied
to the distributor due to leakage past the diaphragm.  This
will cause increased NO   emissions (Ref.  2, 3 and 27).
                       rt

3.7.10.6  Distributor Starting  Solenoid

          The distributor starting solenoid is  a mechanical
advance mechanism to provide additional  spark advance during
engine cranking.  This improves engine starting while
maintaining low HC and CO emissions during idle.  The
advance is provided by a solenoid directly connected to the
vacuum advance linkage.   Failure of the  solenoid will result
in normal advance (none) during starting, but will not
increase emissions significantly unless  the engine stalls
after starting (Ref. 3 and 27).
                          3-65

-------
3.7.10.7  Thermal  Vacuum Valve

          All  manufacturers use thermal  vacuum valves in a
variety of applications.  Valves which are part of major
control systems were categorized under that system's des-
cription.   However,  some thermal vacuum valves are incor-
porated in special  purpose systems or used only to provide
hot coolant temperature override of retarded spark.   These
valves are included  in this category (Ref. 3 and 27).

3.7.10.8  Distributor Vacuum Valve

          The  distributor vacuum valve is  similar to the
distributor vacuum deceleration valve described above,  but
is used to modulate  part throttle advance  rather than decelera-
tion advance.   The valve selects ported vacuum at open
throttle acceleration but switches to the  EGR port at higher
vacuum.  This  change in vacuum source at part throttle
cruise improves driveability of vehicles.   Failure of the
distributor vacuum valve would result in slightly increased
emissions  of NO  and ported vacuum at all  times (Ref. 3 and 27)
               /\
3.8       EMISSIONS-RELATED PARTS LIST

          The system descriptions, probable defect conditions,
and the effect of defects on emissions discussed above were
used to identify emissions-related components.   Although
nearly all components can have some effect on emissions, not
all can cause an emissions failure.  An emission failure
depends on both the increase from baseline and  the relationship
of the baseline to the applicable standard.  Therefore, all
components which appeared to have more than a negligible
effect on one or more pollutant were included in the emissions-
related parts list presented in Table 3-1.
                          3-66

-------
Table 3-1.   EMISSIONS-RELATED PARTS LIST
       ORIGINAL EQUIPMENT PARTS
PART OR COMPONENT
Carburetor System
Idle Stop Solenoid
Throttle Dashpot
Throttle Positioner
Metering Jets
Metering Rods
Vacuum Break Valves
Choke Mechanism
Accelerator Pumps
Power Valves
Gaskets
Float and Valve
Idle Adjustment
Heat Riser
Idle Enrichment System
Electric Assisted Choke
Staged Choke Pulldown
Fuel Filter
Ignition System
Points
Condense r/Capaci tor
Distributor Cap
Distributor Rotor
Mechanical Advance Mechanism
Vacuum Advance Mechanism
Distributor Drive Mechanism
Magnetic or Optical Triggers
Spark Plugs
Ignition Wires
Coil - Inductive
Ballast Resistor
Ignition Timing Adjustment
Spark Delay Valve
Air Induction System
Thermos tatical ly-Controlled
Air Inl et
Vacuum Motor and Hoses
Air Cleaner Element
Turbochargers
RELATED EMISSION
HC

X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X

X
X
X
X


X
X
X
X
X
X
X
X


X
X
X

CO

X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X

X
X
X
X
X
X
X
X
X
X
X
X




X
X
X

NOX































X
X






Smoke






































X
                  3-67

-------
Table 3-1.   EMISSIONS-RELATED PARTS LIST
 ORIGINAL EQUIPMENT PARTS (Continued)
PART OR COMPONENT
Fuel Injection System
Accuml ator
Fuel Pressure Sensors/Regulators
Throttle Linkage and Valve
Injection Valves
Air Sensors/Switches
Temperature Sensors/Switches
Injectors
Triggering Switches
Starting Valve
Idle Adjustment Screws
Engine System
Valve Lifters and'Springs
Cams
Valves, Guides and Seats
Seats
Rings
Gaskets
Camshafts
Emission Control System
PCV Valve
PCV Hoses
PCV Fresh Air Filter
A I Distribution Manifold
AI Hoses
AI Inlet Filter
AI Check Valves
AI Bypass/Di verter Valves
AI Gulp Valves
AI Pump
EVAP Canister Body and Carbon Media
EVAP Hoses
EVAP Fresh Air Filter
EVAP Vapor/Liquid Separator
EVAP System Vapor Control Valves
EVAP Fuel Tank Cap
EGR Valves or Orifices
EGR Hoses, Gaskets, Seals
EGR Temperature-controlled Valve
EGR Solenoid-Controlled Valve
RELA 'ED EMISSION
HC


X
X

X
X
X
X
X
X

X
X
X
X
X
X
X

X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X

X


CO


X
X

X
X
X
X
X
X

X
X
X
X
X
X
X

X
X
X
X
X
X
X
X
X
X

X








NOX








X



























X
X
X
X
Smoke

X
X
X
X







X
X
X
X
X
X
X





















                  3-68

-------
Table 3-1.  EMISSIONS-RELATED PARTS LIST
 ORIGINAL EQUIPMENT PARTS (Continued)
PART OR COMPONENT
Emission Control System (Cont'd)
EGR Temperature Switch
EGR Speed/Transmission Switch
EGR Time Delay Control
EGR Vacuum Amplifier
EGR Vacuum Reducing Valve
EGR Carburetor Spacer
EGR Back Pressure Sensor
EGR Check Valve
TCS Vacuum Solenoid
TCS Vacuum Lines and Hoses
TCS Time Delay Control
TCS CEC Valve
TCS Temperature Control Valve
TCS Transmission Switch
TCS Reversing Relay
SCS Vacuum Solenoid
SCS Vacuum Lines
SCS Time Delay Control
SCS Speed Sensing Switch
SCS Temperature-controlled Valve
OSAC Vacuum Orifice Valve
OSAC Vacuum Hoses
OSAC Thermal Valve
OSAC Vacuum Bypass Valve
OSAC Temperature Sensor
ESC Electronic Module
ESC Hoses
ESC Vacuum Valves
ESC Temperature Sensing
ESC Speed Sensing Switch
CAT Body
CAT Active Media
Heat Riser
Decel Valve
Distributor Vacuum Deceleration Valve
Distributor Starting Solenoid
Thermal Vacuum Valve
RELATED EMISSION
HC




X




X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
CO










X

X




X




X




X



X
X
X
X

X

NOX

X
X
X
X
X
X
X
X
X
X
X

X
X
X
X

X
X
X
X

X
X
X
X

X
X
X




X

X
Smoke






































                  3-69

-------
                       Section 4

             EMISSION-CRITICAL COMPONENTS
          The emissions-related components described in
Section 3 were ranked in the order of their criticality in
causing excessive emissions.  The ranking was based on the
following four factors:   increase in emissions, component
usage, probability of failure and probability of repair.
This section describes the model  used to rank the components,
the values assigned to the input  parameters of the model,
and the resulting rank-ordered lists of emission-critical
components .
4.1       CRITICALITY INDEX MODEL

          A computer model  was developed to select the most
emission-critical  components.   This model  calculated a
criticality index  for each  component and then ranked the
indices in descending order.  Separate rank-ordered lists
were prepared for  each pollutant (HC, CO,  NO ,  smoke) and
                                            A
for early model-years (1972 through 1974), late model-
years (1975), and  a sales weighted composite of 1972 to 1975
model-years.  The  general flowchart of the model  is shown in
Figure 4-1.  Specifically,  the model performed  the following
functi-ons :

          •    Read-in data by engine family and  part code.
                         4-1

-------
 VEHICLE  PRO-
 DUCTION  AMD
 SALES DATA
   COMPONENT
  USE SOURCE
   DOCUMENTS
 MFC REQUIRED
  MAINTENANCE
    SCHEDULES
'STANDARDS &
TOTAL VEHICLE
 POPULATION
  COMPONENT
USE BY ENGINE
   FAMILY
 PUBLISHED
LITERATURE
'REPLACEMENT
FREQUENCY BY
ENGINE FAMILY
 OTHER  PARA
  VALUES BY
  PART  CODE
                              ARRANGE DATA
                              INTO WORKING
                              .   ARRAYS


LIST ENGINE
CONFIGURATIONS
&THEIR CONTROL
SYSTEMS 	



LIST ASSUMED
VALUES BY
PART CODE
I J?^



1
LIST NO. OF
TIMES COMPONENT
JSE WAS NON-
ZERO ^ 	 '
sf
             Figure 4-1.  CRITICALITY MODEL FLOWCHART
                                  4-2

-------
                         READ
                         INPUT
                         TAPE
                      CALCULATE CI
                      1th POLLUTANTS!
                      jth PART CODE
          j=l,130
        = 1,4
Figure 4-1.   CRITICALITY  MODEL FLOWCHART (Continued)
                           4-3

-------
                        RECALL
                        STORED
                          CI
CI
                                                    SAVE RANK
                                                     BY PART
                                                      CODE
                      LIST TOP  50
                      IN PRINCIPAL
                      SORT ORDER
                 NO
    1 = 1,4
                       LIST CI AND
                      RANK IN PART
                      NUMBER ORDER
                    CSTOPJ
Figure  4-1.   CRITICALITY MODEL  FLOWCHART (Continued)
                         4-4

-------
          •    Calculate a criticality index (CI) by pol-
               lutant for each part.
          t    Rank the CI values in  descending order
          • .   Print lists of rank-ordered  parts by pollut
               ant and model-years group.

          The model can readily be expanded to  include
additional  component categories, pollutants, and model
years.

4.1.1     Criticality Index

          The criticality index (CI)  was  a  dimensionless
number representing the relative criticality of each part.
The CI was  calculated as follows:
where :
          CIu •   • (PFJ>  ' (PV
          CI..      Represented the  relative  criticality  of
            1J           fn
                    the j    part or  component in  affecting
                    the emissions of the  i    pollutant.
          E..       Represented the  estimated  impact  on
           1J                         +• h
                    emissions  of the i    pollutant  by a
                    defect in  the j    part  or  component.
          PF.       Represented  the  estimated  probability
            J                 th
                    that the j    part or  component  would
                    become defective prior  to  the end  of  its
                    design life.
                         4-5

-------
          PRJ
                    Represented the probability that the j
                    defective component would not be repaired
                    prior to the end of its design life.
4.1.2
                    Represented the sales volume factor for
                    the j    component.
               Emission Increase Factors
          The emission increase factors (E.-j)  were based on
                                          ' J
the expected change in emissions with respect  to the emission

standards applicable to the engines or vehicles using the

specific component.  The values of E.. and corresponding

emission increase criteria are shown in Table  4-1.
   Table 4-1.   CRITERIA FOR EMISSION INCREASE FACTORS
   E VALUE
                          EMISSION INCREASE
     0.0



     0.1


     1.0


     2.0


     5.0


    10.0
               No change or decrease in emissions
               from defect (vehicle may be disabled
               by defect in this component).

               Emissions may increase but probably
               not enough to fail  standard.

               Slight emission increase (enough to
               fai1 standards ) .

               Moderate emission increase (about
               twice the standard).

               Substantial emission increase
               (several times the  standard).

               Severe emission increase (order of
               magnitude higher  than standard).
                         4-6

-------
The emission increase factors were determined independently
for pre-1975 (noncatalyst)  and post-1975 (catalyst-equipped)
vehicles since these model-year groups reflected significant
differences in emission standards and control system config-
urations.  The emission increase factors for each component
were assigned on the assumption that other components were
not defective.
          For the HC criticality rankings, the evaporative
emission increase factor for each component was  combined
with the corresponding exhaust emission increase factor as
follows:

          EHC = EHC + 1/3 EEVAP

          The smoke emission increase factors for each test
mode were averaged to provide a composite smoke  emission
increase factor as follows:
                smoke =
                        E        E          E
                         accel +  lugging +  peak
4.1.3     Probability of Failure Factors

          The probability of a component's failure (PF.) prior
                                                      J
to the expiration of its design life was estimated on the
basis of durability data, available published data, and
Olson's experience during inspection and maintenance studies.
Probability of failure was based on defects and excluded
failures due to tampering.  The design life of each part or
component was assumed to be 50,000 miles or the recommended
replacement interval of the part, whichever was lower.
Based on the available data and engineering judgement,  a
relative factor representing probability of component failure
was assigned using the criteria shown in Table 4-2.  The same
PF. factors were assigned to components for all model years.
  J

                         4-7

-------
Table 4-2.   CRITERIA FOR PROBABILITY OF FAILURE FACTORS
  PF VALUE
               PROBABILITY  OF FAILURE
    0.01
    0.10
    0.30



    0.50


    0.70


    0.90
     Failure extremely unlikely during
     component design  life - failure
     typically does  not occur during vehi-
     cle's useful  life (over 100,000 miles)

     Failure very  unlikely during compo-
     nent design life  - failure typically
     occurs late in  vehicle useful  life
     (75,000 to 100,000 miles).

     Failure unlikely  during component
     design life - failure typically
     occurs between  50,000 to 75,000 miles.

     Failure may'occur during component
     design life.

     Failure likely  to occur during compo-
     nent design life.

     Failure very  likely to occur during
     component design  life.
4.1.4
Probability of Repair Factors
          The probability that a defective component would

not be repaired (PR.)  prior to the end of its  design life
                   
-------
Table 4-3.   CRITERIA  FOR  PROBABILITY OF  REPAIR FACTORS
 PR VALUE
              PROBABILITY  OF  REPAIR
   0.10


   0.30



   0.50


   0.70


   0.90
     Repair extremely  likely  due  to severe
     performance  impact.

     Repair likely  due  to  performance
     impact and  routine diagnostic/service
     procedures.

     Repair may  occur  depending on diag-
     nostic/service procedure and skill.

     Repair unlikely due to small perform-
     ance impact  or unusual failure mode.

     Repair very  unlikely  due to  small
     performance  impact and unusual
     failure mode.
4.1.5
Sales  Volume  Factors
          The sales  volume  factor  (V.) for each part was not
                                   J
readily available  due  to  the  large number of manufacturers

and models of each component  type.  Therefore, V- was based
                                                 •   •  
                       P

                     £
                      K=l

-------
          n..        Represented the number of j    components
           JK                                 th
                    used on an engine of the k   engine
                    family.
          R..        Represented the number of replacements of
           J             L, u                            4- U
                    the j    component required by the k   engine
                    family during its 50,000-mile design
                    1 i f e .
          S.         Represented the scrapage factor of the
                     t h
                    k   engine family in 1976.

          j         Represented the component index (1 to
                    133).

          k         Represented the engine family index (1 to
                    P, U.)
                        J
                    P  = engine families in population
                    U. = engine families with component j
                         (0 *= U.^ P)
                               J

          In performing this study, the engine  families
listed below were excluded in order to reduce the amount of
data required.   Exclusion  of these engine families was not
believed to introduce significant error since similar basic
engine components were used on these engines as on those
which were included in the study.
          t    Light-duty gasoline engine families whose
               manufacturers produced less than 1 percent of
               sales in any given year.
          0    All light-duty diesel  engine families.
          •    All heavy-duty gasoline engine families.
          •    All but the 15 most popular heavy-duty diesel
               engi ne fami1i es .
                          4-10

-------
4.2       ASSIGNMENT OF CRITICALITY INDEX MODEL PARAMETERS

          This paragraph describes the values of the CI model
input parameters assigned to each OEM component.  These
values are based on the characteristic defect or failure
mode described in Section 3.  Pertinent literature is cited
where available.  However, many of the assigned values are
based on engineering judgement.  The resulting rank-ordered
lists of emission-critical OEM components are presented and
discussed in paragraph 4.3.   Appendix B summarizes the input
parameter values by part name.

4.2.1     Effect of Defect on Emissions

          Each OEM component category was assigned an emis-
sion increase factor for each of the following pollutants:

          •    Gasoline Engines
               Evaporative hydrocarbons
               Hydrocarbons
               Carbon monoxide
               Nitrogen oxides

          t    Diesel Engines
               Acceleration  smoke
               Lugging smoke
               Peak smoke (post-1974 model-year engines)

          The smoke emission increase factors were assigned
only to components on heavy-duty diesel engines.  Components
used only on gasoline engines were assigned 0.0 values for
the smoke emission increase  factors.  Separate emission
increase factors were assigned to early model-years (1972
through 1974 for light-duty, 1972 through 1973 for heavy-
duty) and late model-years (1975 for light-duty, 1974 through
1975 for heavy-duty) to reflect different engine/emission
                         4-11

-------
control  system configurations corresponding to the different
emission standards.

4.2.1.1    Carburetion Systems

          Carburetion systems included completely assembled
carburetors, carburetor components, and carburetor (throttle)
control  devices.  Complete carburetors were not treated in
this analysis since  the major components of the carburetor
were each treated individually.   Specific emission increase
factors  for HC, CO and NO  are discussed below for the follow-
                         rt
ing components based on the functional description and charac-
teristic defects described in Section 3.2.   Similar emission
increase factors were assigned to components in which the
defect would have similar effect.

          •    Idle  stop solenoid
          •    Throttle dashpot
          •    Throttle positioner
          0    Metering jets
          •    Metering rods
          t    Vacuum break valves
          •    Choke mechanism (except electric assists)
          «    Accelerator pump
          9    Power valve
          «    Gaskets
          9    Float and valve
          «    Idle  adjustment screws
          0    Idle  enrichment systems
          «    Fuel  filter

          Idle Stop  Solenoid:  The idle stop solenoid defect
would result in excessive throttle closure (anti-dieseling )
during idling.  This results in  excessively rich operation at
idle.  A defective idle 'stop solenoid was identified as the
                         4-12

-------
HjC
0.1
1.0
cp_
1.0
1.0
— X
0.0
0.0
cause of emissions failure of a catalyst-equipped vehicle
(Ref. 93).   A recent study (Ref. 17) indicates that a 1 percent
CO increase in idle CO concentration approximately doubles
the hot 1972 FTP emissions of CO from all  vehicles and HC
emissions from catalyst vehicles.   Emissions of NO  from all
                                                  J\
vehicles and HC emissions from noncatalyst vehicles were not
affected.  These results generally confirm the CRC APRAC
CAPE-13 study (Ref. 16) performed  on pre-1972 model-year
vehicles.  Based.on these data, the following emissions
increase factors were assigned:
          1972-1974
             1975
          Throttle Dashpot and Positioner^:   Defective  dashpots
result in more rapid throttle closure during deceleration.
Defective throttle positioners result in full  throttle closure
during decelerations.   These defects result in momentary
enrichment (Ref. 3) causing high HC and CO  during deceleration
No data was obtained which related defective dashpots  or
throttle positioners to increased emissions.  However, it was
assumed that the defect would be similar to overall  idle
enrichment except that catalysts would be able to reduce the
HC increase.  Therefore, the following emission increase
factors were assigned  to both throttle dashpots and  throttle
positioners :
          1972-1974
             1975
          Metering Jets:   Defective metering jets result in
mixture enrichment and higher CO.   However, except in the
case of incorrect jet size installed in the carburetor',
                         4-13
HC_

0.1
0.1
CO
— ' •
1.0
1.0

— x
0.0
0.0

-------
HC_
0.1
0.1
co.
0.1
0.1
— x
0.0
0.0
erosion of the jet by cavitation or entrained participates is
slow and the effect on emissions is small.   No data exists
relating jet size changes to FTP emissions.   Therefore,  engi-
neering judgement was used to assign the following factors for
defective jets:
          1972-1974
             1975
          Metering Rods:   Defective rods  result in  mixture
enrichment similar to eroded jets.   Since the  rod  position is
adjustable, the consequence in terms of incorrect  orifice
size and metering rate is  greater for rods  than for jets.
Therefore, larger CO emission increases were  assigned  to
defective rods than to defective jets.   The same factors were
assigned to noncatal.yst and catalyst vehicles  since the
effectiveness of the catalyst in controlling  excessive
emissions is balanced by  more stringent standards:

                              Mi        £0.        Mx
          1972-1974          0.1       2.0         0.0
             1975            0.1       2.0         0.0

          Vacuum Break Valves:  Defective vacuum break
valves result in normal thermostatic choke  opening  rather
than load or temperature  modulated  opening.  This  results in
longer and richer warm-up  and higher cold-start emissions of
HC and CO.  The CO emission increase relative  to the standards
should be greater on catalyst-equipped  vehicles than on
noncatalyst vehicles because of the large weighting of cold-
start emissions.  The HC  emission increase, however, should
be small since the vacuum is above  the  throttle plate  (Ref. 27)
The following emission increase factors were,  therefore,
assigned :
                          4-14

-------
                              HC^        CO        NO
          1972-1974          0.1       0.1        0.0
             1975            0.1       1.0        0.0

          Choke Mechanism:   Defective chokes cause higher HC
and CO emissions due to fuel enrichening particularly during
open-throttle operation.   The degree of emission increase
depends on engine size and emission control system.   This
defect may also result in accelerated catalyst aging for
catalyst-equipped vehicles as well as higher emissions (Ref.
12, 16, 17, 70, 78, 92, 93 and 100).  The HC/CO emission
increase factors were, therefore, assigned as follows:

                              HC.        PJ).        N£x
          1972-1974          2.0       10.0       0.0
             1975            2.0       10.0       0.0

          Accelerator Pump:   Defective accelerator pumps
result in intermittent lean  operation during the initial
throttle opening of acceleration.  This may result in momen-
tary lean misfire and higher HC.   Emissions of CO from non-
catalyst-equipped vehicles will  decrease due to the  additional
oxygen and dilution of the exhaust (Ref.  78).  Catalysts
should be able to partially  oxidize the HC emissions, thereby,
resulting in slightly higher CO  emissions (Ref. 70).   The
following emission increase  factors were, therefore, assigned.

                              Hi        CO        N0_x
          1972-1974          0.1       0.1        0.0
             1975            0.1       0.1        0.0

          Power Valves:  Defective power valves result in
excessive fuel flow at all  off-idle conditions.  Although no
specified data were obtained, the result is similar  to choke
failure (Ref. 70 and 78).  Therefore, the same emission
increase factors were assigned for power valves as were
assigned for a-e^ol orator pinnus1.

                         4-15

-------
                              HC.        C0_        N£x
          1972-1974          2.0       10.0        0.0
             1975            2.0       10.0        0.0

          Gaskets:   Defective gaskets  result in  vacuum leaks
and lean misfire at closed throttle (high  vacuum).   The
resulting increase  in mass emissions  though  is  small  due to
the small effective size of the leak  and because it occurs
primarily during closed throttle (Ref.  27).   No  specific data
on gasket failures  were obtained,  the  failure is expected to
be similar to lean  misfire from defective  accelerator pumps.
Therefore, the following emission  increase factors  were assigned

                              HC^        CO.        Nl
          1972-1974          0.1       0.0        0.0
             1975            0.1       0.1        0.0

          Float and Valve:  Defective  floats result in excess
fuel flow during all  load conditions.   However,  the effect  on
emissions at idle generally is less than incorrect  idle
adjustment (and can be compensated for  by  idle  adjustment),
and is less than the  choke or power valve  defects under load.
No data was obtained  relating specific  float level  misadjustment
to FTP emission levels.  However,  the  same emission increase
factors have been assigned to a defective  float  and valve as
were assigned to defective metering rods.
          1972-1974
             1975
          Idle Adjustment:  Improper idle adjustment can
result in either rich or lean operation.  The emission increase
depends on the degree of misadjustment,  the engine size, and
emission control system.  Rich adjustment, however, is much
                         4-16
hi
0.1
0.1
C_2
2.0
2.0
N0x
0.0
0.0

-------
more common as shown by surveillance and inspection programs
(Ref. 12, 16, 78 and 94).   The emission increase factors were
based on the assumption of moderate maladjustment (i.e., 1 to
2 percent CO at idle) and  were as follows (Ref.  16, 70 and
93):
1972-1974
1975
HC
0.1
1.0
C£
1.0
1.0
N0x
0.0
0.0
          Idle Enrichment System:  Defective idle enrichment
systems can result in excessive enrichment at all temperatures
rather than at low temperature only (Ref.  27).   This is
equivalent to excessively rich idle adjustment.   The same
emission increase factors as above were, therefore, assigned:

1972-1974-
1975
HC.
0. 1
1 .0
CO
1 .0
1 .0
NO
— x
0.0
0.0
          F^uel Filter:  The defect mode results in reduced
fuel flow to the carburetor causing lean operation and power
loss under heavy load conditions.   On gasoline engines flow
restriction may lead to slight increases in HC emissions but
no change or decreases in CO and NO  emissions.  On diesel
                                   y\
engines, flow restriction can lead to power loss but not
increased smoke since excess air is already present (Ref.  2
and 3).  The following emission increase factors were, there
fore, assigned.


1972-1974
1975
HC
' '-—
0.1
0.1
CO
	
0.0
0.1
N.O
— x
0.0
0.0
Smoke
	
0.0
0.0
                         4-17

-------
4.2.1.2   Ignition System

          Defects in the ignition system can lead to misfire
and increased HC emissions.   Some defects can affect the
timing of the ignition spark and, consequently, NO  emissions
Some defects leading to misfire or changes in spark timing
may also increase CO emissions due to the increased throttle
opening which is required to maintain desired speed and load
conditions.  Catalysts are generally able to oxidize HC
emissions more easily than CO.  Therefore, some of the
unburned fuel may be oxidized resulting in smaller increases
in HC and larger increases in CO emissions than expected
compared to noncatalyst-equipped vehicles.
          Separate paragraphs are devoted to the following
OEM ignition system components:

          •    Points
          •    Condenser
          •    Distributor cap
          •    Distributor rotor
          •    Distributor mechanical advance
          •    Distributor vacuum advance
          •    Spark delay valves
          •    Electronic ignition triggers
          •    Spark plugs
          •    Igni tion wi res
          •    CoiIs
          •    Ballast resistor
          •    Electronic ignition circuits
          ••    Basic ignition timing

          The above components can generally be divided into
primary  ignition components,  secondary  ignition components,
and distributor  timing components.   In  general, primary
ignition component defects do not cause as severe misfire as
                         4-18

-------
a secondary ignition defect which may essentially disable
one cylinder.   Specific data relating defects to emission
increases were not available for individual  primary ignition
system components.  However, since misfire is distributed
intermittently over all cylinders, the emissions increases
should not be  as severe as for plugs  or wires.
          primary Ignition Components:  The  primary ignition
system includes points, condenser, coil, ballast resistor
and distributor drive mechanisms which affect point operation.
These components were all  assigned the same  emission increase
factors because specific data on each component was not
available, and all components generally cause a random
intermittent misfire in the secondary ignition  system.   The
actual emission increase on any specific vehicle or engine
depends on the deviation of the component from  specification,
the number of cylinders, and the emission control system
configuration.
          Misfire on pre-catalyst-equipped vehicles generally
causes HC emissions to increase with  little  or  no change in
CO and NO  (Ref. 12, 78, and 94).  On catalyst-equipped
         A
vehicles, however, the catalyst should be able  to partially
oxidize the HC emission increase (Ref. 15) resulting in a
small increase in both HC and CO.  Emissions of NO  should
not be significantly affected by intermittent misfire (Ref. 7,
15, 35, and 70).  Therefore, the following emission increase
factors were assigned to the primary  ignition components
described above:
          1972-1974
            1975
          j)i stri b^utor Rojtor__and_C_ap :  A defective distributor
cap and/or rotor increases the resistance of the secondary
ignition circuit and reduces the available firing voltage at
HC_
1.0
0.1
CO
0.0
0. 1
NO
— x
0.0
0.0
                         4-19

-------
HC_
2.0
2.0
CO
0.0
0.1
N°_x
0.0
0.0
the spark plug.   No data was obtained relating rotor or cap
failure to FTP emissions.   However, frequent misfire on one
or more spark plugs (usually the plug/wire with highest
internal resistance) may result if severe cap or rotor
deterioration occurs.   Frequent misfire  causes moderate
increases in emissions of HC (Ref. 3, 7, 16, 70, 78, and
92).   Changes in CO or NO  emissions are small.  Therefore,
                         A
the following emission increase factors  were assigned to
both the rotor and cap:
          1972-1974
            1975
          Distributor Mechanical/Vacuum Advance:  Defective
mechanical or vacuum advance including dual diaphragm advance
results in incorrect or no spark advance as engine speed
and/or load increase from idle (Ref. 3).  This is equivalent
to improper (retarded) basic timing which can effect HC, CO
and NO  emissions depending on engine speed and/or load
      A
condition.  The change in timing due to a defective advance
mechanism may lead to misfire but is more likely to affect
the time of combustion with respect to valve opening.
Emissions of HC decrease due to late firing and smaller
surface to volume ratios.  Emissions of NO  decrease due to
                                          A
the combustion occurring at lower compression ratios than
normal.  Emissions of CO increase because additional throttle
angle is required and mass flow rates are higher.  The follow-
ing emission increase factors were, therefore, assigned to
distributor advance mechanisms.
          1972-1974
            1975
HC_
0.0
0.0
CO
0. 1
1.0
N0x
0.0
0.0
                         4-20

-------
          Spar k Del ay_Va1y^es :   Defective spark delay valves
result in normal vacuum advance during initial throttle
opening.   This increases NO  emissions somewhat and may also
                           y\
increase  HC emissions slightly (Ref. 3 and 27).  Similar
emission  increase factors were assigned for spark delay
valves as were assigned for advanced timing and defective
OSAC valves since they result  in advanced timing.

                              ur        r n        iun
                              n.k.        ky.        NUx
          1972-1974           0.1       0.0       1.0
            1975              0.1       0.0       1.0

          Electronic Ignition  Trigger:  No data was obtained
relating  failures of the electronic ignition to emissions.
Defective electronic ignition  triggers, however, can cause
intermittent misfire since a plug will not fire if the
trigger signal is missing (Ref. 46).  The same emission
increase  factors assigned to spark plug and wires were,
therefore, assigned to electronic ignition triggers:

                              hi        kP_        NO.
          1972-1974          10.0       0.0       0.0
            1975             10.0       0.1       0.0

          S^park PI ugs/Wi res :  Defective plugs or wires cause
ignition  misfire.  Typically,  one cylinder is affected because
of an open or shorted wire or  a fouled plug.  This can
result in continuous HC emissions, in excess of 2,000 ppm C, ,
which is  equivalent to 20 or more grams per mile by the FTP.
In addition, for some catalyst-equipped vehicles, total
misfire on one cylinder may damage the catalyst if continued
for an extended period and if  the over temperature protection
system (air dump) fails.  Emissions of NO  may increase
but not enough to fail (Ref. 16, 78, 92, 93, and 100).  On
catalyst  ve-hicles, the excess  HC emissions may be partially

                          4-21

-------
oxidized to CO.   Therefore,  the following emission increase
factors were assigned to defective plugs and wires:

                              HC_        C_0        IWx
          1972-1974          10.0       0.0       0.0
            1975          .   10.0       0.1       0.0

          Ignition Timing:  Defective (advanced) basic
ignition timing  results in increased idle emissions and may
also increase cruise emissions due to errors in total advance
(Ref. 3 and 27).  The CAPE-13-68 study (Ref. 16) showed that
timing advance increased HC  and NO  mass emissions but
                                  y\
decreased CO.  These results were partially confirmed for
catalyst vehicles in recent  studies (Ref. 17 and 100) which
showed that advanced timing  decreased CO,.did not signifi-
cantly affect HC, and increased NO  slightly.  Other studies,
                                  A
however, showed  that advanced timing increased HC and CO as
well as N0x (Ref. 92 and 98).   Retarded timing reduces NOX and
generally increases HC and CO (Ref. 92, 98 and 100).  The
following emission increase  factors were assigned for basic
ignition timing  since advanced timing is the most probable
fai1ure condi tion :
          1972-1974
            1975
4.2.1.3   Air Induction System

          Defects in the air induction system can result in
either excessively lean or rich carburetion depending on the
component.  The emissions-related components of the induc-
tion system are:

          •    Thermostatic Air Cleaner including shroud and
               hose, thermostat, vacuum motor, vacuum hoses,
               fresh air inlet
                         4-22
•Hi
0.1
0.1
cp_
0.0
0.0
— x
1.0
1.0

-------
          •    Air cleaner element
          t    Turbochargers

          T_AC Shroud, Hose, and Thermostat:  Failure of
these components affects only the cold start FTP results.
No data was available relating defects in these components
to emissions.  However, the expected affect is lean misfire
due to mixture enleanment from unheated dense air (Ref. 3
and 27).  The effect on CO and NO  emissions is expected to
                                 A
be negligible.  Vehicles equipped with catalysts are more
sensitive to cold start emissions.  Therefore, the following
emission increase factors were assigned to these components:
1972-1974
1975
H£
0. 1
1.0
CO
0.0
0.0
N0x
0.0
0.0
          TAC Vacuum Hoses and Vacuum Motor;  Defective
vacuum hoses or vacuum motor produce a vacuum leak in the
intake manifold in addition to preventing rapid warm-up.
The leak is present at all operating temperatures and,
therefore, has more effect on HC emissions than the other
TAC components which only influence cold start performance
(Ref.  3).   The HC and CO emissions will  probably decrease on
noncatalyst vehicles but CO emissions may increase slightly
on catalyst vehicles due to partial oxidation of the HC
emissions.  NO  emissions will probably  not be affected
              A
(Ref.  92 and 93).   The following emission increase factors
were,  therefore, assigned:


1972-1974
1975
HC
— — -
0. 1
1.0
CO

0.0
0. 1
NO
- — x
0.0
0.0
                         4-23

-------
          TAG Fresh Air Inlet:   A defective TAG air inlet
for underhood, or cool  air, results in hotter than normal
air being drawn into the engine.  This will cause a decrease
in air density and, consequently, mixture enrichment (Ref.  2)
This will increase CO and HC emissions slightly, but decrease
NO .  No data was obtained on the relation of this defect to
  A
emissions.   However, the HC and CO emissions increase for
catalyst vehicles were  assigned the same value  as for non-
catalyst vehicles since reserve activity of the catalyst
should compensate for the slightly higher emissions.  There-
fore, the following emission increase  factors were assigned:
1972-1974
1975
H£
0. 1
0.1
CO
0. 1
0. 1
NOX
0.0
0.0
          Air Cleaner Element:   The air cleaner element is
subject to clogging which reduces the air flow under any
given vacuum.  This has the effect of decreasing the air-
fuel ratio which increases CO and HC emissions but decreases
NO  emissions.   However, a previous study (Ref. 16)7 has
  A
shown that substantial  restriction of the air cleaner is
required before significant changes are observed in CO
emissions.  Catalytic reactors  are expected to partially
control CO emission increases.   Some carryover of high CO
into HC may also occur.  The actual emission increase is
highly dependent on the engine  size control system configura
tion, and degree of restriction (Ref. 92, 92 and 100).
Therefore, the  following emission increase factors are
assigned which  are the  same as  those assigned for metering
rods, float and valve in the carburetor:
1972-1974
1975
HC_
0. 1
0.1
CO
2.0
2.0
NP_X
0.0
0.0
                         4-24

-------
1972-1973
1974-1975
1.0
1.0
0.0
0.0
          The air cleaner also can affect smoke emissions
from diesel engines due to the fuel enrichment which occurs
when the air cleaner is clogged (Ref. 2 and 3).  This effect
is independent of the model-year and is significant only for
the acceleration and peak smoke measurements (Ref. 3).  The
following smoke emission increase factors were assigned:

                              ACCEL     LUGGING   P_EAK

                                                  1.0

          Turbocharger^:  The turbocharger increases the
volumetric efficiency of the engine due to pressurizing the
intake manifold (Ref. 2).  However, it only functions
during acceleration or high load conditions.  Defective
turbochargers would be expected to reduce the air pumped
through the engine and, thereby, result in mixture enrichment
(Ref. 2).  The smoke emission increase factors are shown
below:

                              ACCEL     LUGGING   PE!AJ<

                                                  1.0

4.2.1.4   Fuel Injection Systems

          Fuel injection systems are used in both gasoline
and diesel engines.  Fuel injection systems may be mechani-
cally operated (MFI) or electrically operated (EFI).  Gasoline
engines use either MFI or EFI.  Diesel engines, however, use
MFI.  Defects in these systems generally result in excess
fuel supply leading to excessive CO, HC and smoke emissions.
Conditions of insufficient fuel supply produce unacceptable
driveability problems and are rapidly corrected by owners.
Emission increase factors were, therefore, assigned for the
more typical failure;  i.e., excess fuel metering.
                         4-25
1972-1973
1974-1975
1.0
1.0
0. 1
0.1

-------
          The following fuel  injection components are dis-
cussed below:

          •    Accumulator
          •    Fuel  pressure  sensors/regulators
          •    Throttle linkage and valve
          •    Injection valves
          •    Air sensors/switches
          •    Temperature sensors/switches
          •    Injectors
          •    Triggering switches
          §    Starting valve
          •    Idle  adjustment screws

          Accumulator:   The accumulator is not likely to
fail.  However, if it did fail, overfueling is the probable
result due to pressure  shock  waves developing in the fuel
lines (Ref. 3).  This probably causes slightly higher smoke
emi ssi ons as fol1ows:

                              ACCEL     LUGGING   PEAK

                                                  0.1

          F^uel Pressure SensorVRejju/l ators :  Incorrect fuel
pressure is most likely to cause overfueling, particularly
during acceleration.  Incorrect fuel pressure is analogous
to incorrect float setting.  The peak smoke reading may also
be high.  High fuel  injection pressure in gasoline engines
would cause higher CO and slightly higher HC but lower NO  on
                                                         A
the FTP.  Therefore, the following emission increase factors
were assigned:
1972-1973
1974-1975
0. 1
0.1
0. 1
0. 1
                         4-26

-------
1972-1973
1974-1975
1.0
1.0
0. 1
0.1
                              HC        CO        NO
                              —        —        -—x
               1972-1974     0.1       1.0        0.0
                 1975        0.1       1.0        0.0

                              ACCEL     LUGGING   f^EAJC

                                                  1.0

          T^hrottle Linkage and Valve:  Incorrect throttle
valve adjustment in mechanical injection systems will tend
to overfuel all cylinders.  This is particularly true for
heavy-duty engines in which overfueling can increase the
useful power of the engine.  Higher smoke emission increase
factors were assigned for late-model engines due to tighter
standards.  Overfueling occurs at all load conditions (Ref. 3
and 63).   The following smoke emission increase factors
were, therefore, assigned:
                                                  PEAK
                                                  2.0
          Injection Valves (MFI):  Defective injection
valves result in excessive fueling of individual cylinders
under all operating conditions (Ref.  3).  The most severe
effect probably occurs during low load when the fuel flow is
not completely shut off (Ref. 3).  Therefore, the following
emission increase factors were assigned:

                              ACCEL     LUGGING   P£AK_

                                                  2.0

          Ai rFlow^ or^ Temperature Sensors/Switches (EFI):
Characteristic defects in air or oxygen sensors/switches
                          4-27
1972-1973
1974-1975
ACCEL
1.0
2.0
LUGGING
0. 1
0.1
1972-1973
1974-1975
1.0
1.0
1.0
1.0 .

-------
result in mixture enrichment either due to restricted air
flow (auxiliary air regulator)  or increased fuel  flow (defec-
tive manifold vacuum switch, intake air flowmeter, or 0~
sensor).   Failure of any temperature sensor results in
overfueling because cold start  enrichment continues at all
times (Ref. 3 and 27).   These failures are analogous to
defective power valves  and chokes in carburetors.   The
following emission increase factors were, therefore, assigned
1972-1974
1975
HC.
1.0
1.0
co
5.0
5.0
N0x
0.0
0.0
          Injectors-Solenoid (EFI):   Defective injectors
fail to shut off, thereby, dribbling fuel  at all  times into
the intake manifold or port.  This results in mixture enrich.
ment of at least one cylinder (Ref.  3).   The following
emission increase factors were, therefore, assigned:
1972-1974
1975
hi
0. 1
0. 1
CO
2.0
2.0
NP.X
0.0
0.0
          Triggering Switches (EFI):  The triggering switches
are contacts in the distributor which signal  the time with
respect to TDC at which the fuel  is to be injected (Ref.  3).
Failure of the triggering switches tends to produce lean
misfire particularly at high speed and load.   Catalyst
activity, however, partially oxidizes the increased HC to
CO.  Therefore, the following emission increase factors were
assigned:
1972-1974
1975
MC.
2.0
2.0
CO
0.1
1.0
NOX
0. 1
0. 1
                         4-28

-------
          Smarting Valve:  The starting valve is used for
enrichening the mixture of gasoline engines during cold
start.  A defective starting valve enriches the mixture at
all times.  This is analogous to a partially closed choke
(Ref.  3).  Therefore, emission increase factors were assigned
which  are half of those assigned to chokes:
1972-1974
1975
HC_
1.0
1.0
CO
5.0
5.0
N0x
0.0
0.0
          Idle Adjustment:  Idle air bleed screws are used
on gasoline fuel injection systems for the same reason as on
carburetors.   The same emission increase  factors were
assigned for HC, CO, and NO  as were assigned for carburetor
                           A
idle adjustment.
1972-1974
1975
HC_
0. 1
1.0
C.O.
1.0
1.0
NO
— -x
0.0
0.0
          Idle fuel flow adjustments are also provided for
diesel fuel  injection pumps or throttle valves.   These
adjustments  usually involve bypass pressure relief.  Exces-
sive idle fuel flow causes smoking during the lugging and
deceleration modes of the FTP (Ref. 2 and 3).  The following
emission increase factors were, therefore, assigned:

                              ACCEL     LUGGING   PEAK
               1972-1973       0.1        1.0
               1974-1975       0.1        1.0     2.0
                         4-29

-------
4.2.1.5   Engine Systems

          The following OEM engine components can affect
emissions within the certification design life:

          t    Exhaust valves and associated components such
               as seals, lifters, springs, guides, cams,
               camshafts and timing chains.
          •    Piston rings.
          t    Head gaskets.

          No data was obtained relating defects in these
components to FTP emission levels.  However, design and
development information on the effect of valve operation on
emissions was available in several references.  Emissions
from both gasoline and diesel engines are affected by defects
in these components.  Therefore, values were assigned to
emission increase factors for HC, CO, NO , and smoke.
                                        A
          The components which control valve alignment and
operation include lifters and springs, valve cams and cam-
shafts, and valve guides.  These components, if defective,
cause the valves to open and close incorrectly resulting in
loss of unburned mixture from one or more cylinders.  This
causes increased HC and smoke emissions.  Defective valve
seals and piston rings allow lubricating oil to enter the
cylinders.  This increases smoke and CO emissions because
the heavy oils do not burn completely.  Defective head
gaskets may allow coolant to enter the engine.  This results
in quenching of the combustion process and increased emissions
of HC, CO, and smoke.  Catalyst  vehicles may also experience
a slight CO emission increase due to partial oxidation of
the HC emissions (Ref. 3 and 15).  The following emission
increase factors were, therefore, assigned to all internal
engine components using engineering judgment:
                          4-30

-------
1972-1973
1974-1975
1.0
1.0
1.0
1.0
                              HC        C_0        NO
               1972-1974     1.0       1.0        0.0
                 1975        0.1       0.1        0.0

                              ACCEL     LUGGING   P^AK

                                                  1.0

4.2.1.6   Emission Control Systems

          The same emission increase factors were assigned
to similar emission control components even though they were
used in different systems.  For example,  all vacuum hoses
were assigned the same factors for HC since a vacuum leak
may be created whether a hose is employed in EGR, TCS, or
Ignition advance applications.  Similarly, transmission or
speed sensors were assigned the same emission increase for
NO  whether they were used in SCS, TCS or EGR applications.
  A
Some devices may fail in more than one state.  Emission
increase factors were assigned for the failure mode with
either the greatest probability of occurring or with the
greatest effect on emissions.  None of these emission control
systems are used on diesel engines and, therefore, no smoke
emission increase factors were assigned.   The emission
control systems considered were the following:

          •    Crankcase ventilation (PCV)
          •    Evaporative emission (EVAP)
          •    Air injection (AIR)
          •    Exhaust gas recirculation  (EGR)
          •    Transmission/speed controlled spark (TCS)
                         4-31

-------
          •    Orifice spark advance control  (OSAC)
          •    Electronic spark control  (ESC)
          t    Catalytic reactors (CAT)
          •    Manifold heat control (Heat riser)
          •    Electric assist choke
          •    Staged choke pulldown
          •    Decel  valve
          t    Distributor vacuum deceleration valve
          •    Thermal vacuum valves
          •    Distributor starting solenoid
          •    Distributor vacuum valve

          PCV Valve and Breather (Air Inlet):  Restrictions
of the PCV valve or air inlet filter to  the PCV system cause
mixture enrichment since the PCV valve contributes ventilation
air flow to the intake.  The CAPE-13-68  study (Ref. 16)
found that NO -controlled vehicles were  quite sensitive to
             A
PCV restriction for CO, slightly sensitive for HC and insen-
sitive for NO .  No specific data for catalyst-equipped
             A
vehicles were available.  However, PCV restriction is similar
to rich idle adjustment.  The same emission increase factors
assigned idle adjustment were, therefore, assigned to PCV
valves and breathers:
1972-1974
1975
HIC_
0. 1
1.0
CO
1.0
1.0
N0₯
A
0.0
0.0
          PCV and EVAP Vacuum Hoses:  .PCV or EVAP hose
failure (rupture or loosene'ss) results in evaporative emis-
sions and possibly lean misfire.  Under high load, crankcase
vapors may be forced into' the atmosphere.  If an intake
manifold vacuum hose fails, a lean misfire will result due
to the high air flow at idle (Ref. 3).- Catalyst vehicles

                         4-32

-------
have the same evaporative emission increase but slightly
higher CO emissions due to partial oxidation of the hydro-
carbons from misfire (Ref. 70 and 93).  The following emission
increase factors were assigned:
1972-1974
1975
EVAP
10.0
10.0
HC
0. 1
0. 1
CO
0.0
0. 1
N0y
A
0.0
0.0
          jVAP Canjster:  Failure of the carbon canister
involves deactivation or saturation of the activated carbon
so that fuel vapors pass through and out of the canister.
No data was available on the relationship of the EVAP canister
to emissions.   However, no effect on exhaust emissions is
expected.  The following emission increase factors were
assigned on the basis of engineering judgment;
1972-1974
1975
EVAP
10.0
10.0
HC
0.0
0.0
CO
0.0
0.0
NO
A
0.0
0.0
          EJ/AP System Components:  In addition to the carbon
canister and vacuum hoses, the EVAP system includes a fresh
air filter, check valves, and sealed gas cap.  No data was
obtained relating defects in these components to emissions.
Clogging or restriction of the EVAP fresh air filter, however,
reduces the rate of purging and may reduce the activity and
storage capacity of the carbon.  Since clogging will probably
not be complete, lower EVAP emissions increase factors are
assigned than for a defective canister.  Similar affects are
produced by defects in the purge valves vapor/liquid separator,
or fuel tank cap.  The following emission increase factors
were assigned to the above EVAP system components on the
basis of engineering judgment:
                         4-33

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1974-1974
1975
EVAP
2.0
2.0
MC
0.0
0.0
CO
0.0
0.0
NO
— x
0.0
0.0
          Air Injection (AI)  System;  The AI system is
disabled by breakage of the manifold, hoses, fan belts, or
pump.  Failure of the air injection system results in
increased HC and CO emissions but no significant change in
NO  emissions.  Failure of the AI system on catalyst vehicles
  A
causes a large increase in CO and HC emissions particularly
in large engines due to loss  of excess secondary air (Ref. 70,
93, and 100).  The following  emission increase factors were
assigned to the air pump, manifold and hoses:
1972-1974
1975
HO.
1.0
2.0
CJD
1.0
5.0
N0x
0.0
0.0
          Air Injection (AI) Filter and Check Valves:
These AI system components can affect the performance of the
system because they protect_the pump either from entrained
material or from backfiring which  may occur in the exhaust
manifold.  Their failure, however, does not necessarily
defeat the AI system.   Therefore,  the following emission
increase factors were assigned on  the basis of engineering
judgment:

1972-1974
1975
HC_
0. 1
1.0
co.
0.1
1.0
N0x
0.0
0.0
          A_ir Injection (AI) Bypass , Diverter or Gulp
Valves:  These valves are used to prevent backfiring in the
exhaust system and catalyst overheating during engine malfunc-
tions.  Failure of the valves do not affect NO  emissions,
                                              A

                        4-34

-------
but slightly increase HC and CO emissions from noncatalyst
vehicles.   They have potentially great effect on HC and CO
emissions  from catalyst vehicles since the catalyst may be
destroyed  if these systems fail during an engine malfunction
(Ref. 70,  and 100).  Therefore, the following emission
increase factors were assigned:

1972-1974
1975
HC_
0. 1
2.0
C0_
0. 1
5.0
-— x
0.0
0.0
           ^   Valve and Control Components:  Defective EGR
valves have negligible effect on HC and CO but may double or
triple NO  (Ref. 70, 92, 93 and 100).   Valves may either
         A
become clogged (orifice) or stuck (vacuum activated) due to
corrosion, diaphragm rupture or vacuum system failure
(Ref. 70).  The vacuum signal may be modulated for specific
load, speed, and/or temperature conditions.  The control
components include thermal vacuum valves, solenoid valves,
speed/transmission switches, temperature switches, and time
delays.   Failure of any one of these components will defeat
the EGR system by denying vacuum to the EGR valve (Ref. 3
and 27).  Therefore, the same emission increase factors
assigned to EGR valves were also assigned to the above EGR
control  components:
1972-1974
1975
HC
0.0
0.0
CO
0.0
0.0
N0x
2.0
2.0
          E^GR Vacuum Amplifier and Vacuum Hoses:  A defective
vacuum amplifier or vacuum hose creates a manifold vacuum
leak and also defeats the EGR system.  Therefore, the same
emission increase factors used for EGR valves were assigned
to these vacuum components.  The vacuum leak may increase HC
                         4-35

-------
emissions slightly.  However, CO emissions will not increase
due to the excess air and higher combustion temperatures
present without  EGR  (Ref. 2, 3, and 27).  Therefore, the
following emission increase factors were assigned.
1972-1974
1975
HC_
0.1
0.1
CO
0.0
0.0
NOX
2.0
2.0
          EGR Vacuum Reducing Valve, Carburetor Spacer,
    Bac^k Pressure Sensor:  Defective vacuum reducing valves
and back pressure sensors reduce the vacuum signal reaching
the EGR valve.  This reduces EGR but not as much as complete
failure of the vacuum signals.   The carburetor spacer can
become clogged so that EGR does not occur, particularly at a
low pressure differential between intake and exhaust manifolds
Total blockage of the system is unlikely, however, unless
severe oil burning occurs.  There is no significant increase
of HC or CO from these failures (Ref 3 and 27).'  Therefore,
the following emission increase factors were defined for
these components:
1972-1974
1975
.HC
0.0
0.0
CO
0.0
0.0
N0x
1.0
1.0
          EGR Check Valves:  The EGR check valves hold the
highest manifold vacuum achieved during certain operating
conditions.  This reduces  the effectiveness of EGR but not
as much as defective back  pressure sensors or vacuum  reducing
valves  (Ref. 3 and 27).  Therefore,  the following emission
increase  factors were  assigned:
                          4-36

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                              HC        CO        NO
                              —        —        —x
               1972-1974     0.0      .0.0        0.1
                 1975        0.0       0.0        0.1
          TCS, SCS, ESC Solenoid Valves and Control
Components:   Vacuum solenoids are normally deactivated
allowing vacuum advance signals to reach the distributor.
During low speeds, the solenoids are activated to prevent
vacuum advance for NO  control.  Failure of the solenoids
produce normal vacuum advance at all times.  This results in
a slight HC  emission increase and substantial  NO  increases.
                                                /\
Emissions of CO are reduced since average timing is advanced
from normal.  Failure of components which activate the TCS,
SCS, or ESC  solenoids (speed switches, thermal vacuum
valves, and  time delays) also results in total defeat of the
system.  Therefore, the following emission increase factors
were ass igned :
                              IHC_        C_0        N0_
               1972-1974     0.1       0.0        2.0
                 1975        0.1       0.0        2.0

          J_CS, SCS, ESC Vacuum Hoses  Failure  of these
vacuum lines results in manifold vacuum leaks  and loss of
vacuum advance.  This results in reduced NO ,  slightly increased
                                           A
HC due to lean misfire, and higher CO due to retarded timing.
The increased CO is proportionately higher on  catalyst-
equipped vehicles due to the lower standards and partial
oxidation of the HC emissions.  The following  emission
increase factors were, therefore, assigned (Ref. 3 and 70):

1972-1974
1975
HC_
0.1
0. 1
CO
0. 1
1.0
— x
0.0
0.0
                         4-37

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          C_EC Solenoid:  The CEC solenoid, used only on pre-
1975 model-year vehicles, combined the vacuum solenoid and
throttle positioner into one device.   Failure of the solenoid
prevents deceleration throttle modulation and vacuum advance
at all times (Ref.  3 and 27).   This increases HC and CO but
reduces NO  as  shown below:
          A

                              HC_        c_p_        i\mx
               1972-1974     2.0       2.0        0.0

          Orifice Spark Advance Control (QSAC) Valve:  The
OSAC valve delays the rate at which vacuum advance is applied
to the distributor.  Failure of this  device results in
normal spark advance at all  times.  This causes some increase
in NO  but small  effect on HC and CO  emissions.  Vehicles
     A
equipped with OSAC also have other controls; i.e., EGR or
TCS (Ref. 3 and 27).  The following emission factors were,
therefore, defined:

1972-1974
1975
HC
0. 1
0. 1
C_0
0.0
0.0
Mx
2.0
1.0
          Catalytic Reactors (CAT):  Oxidation catalysts are
subject to many failure modes.   Destruction or deactivation
of the catalyst substantially increases HC and CO emissions
without affecting NO  emissions.  Therefore, the following
                    /\
emission increase factors were assigned to the catalyst
active media assuming that other major defects (i.e., misfire),
were not present (Ref. 72):
                              HC_        C_0        N0_x
               1975          2.0       2.0        0.0
                         4-38

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          Manifold Heat Control (_Heat Riser):  The heat
riser aids in cold start warm-up by improving vaporization of
the  fuel.  The heat riser is likely to stick  in the closed
position (hot manifold) which would delay the warm-up of the
intake manifold and cause lean misfire due to vaporization
of only the  lighter fractions of the fuel (Ref. 2 and 78).
This will increase HC emissions during the cold start (Ref.  16)
Therefore, the following emission  increase factors were
assigned:

1972-1974
1975
HC_
0. 1
1.0
cj°_
0.0
0. 1
NO
— x
0.0
0.0
          Electric Assi sted and^ Staged Pulldown Chokes :
Failure of these components results in normal thermostatic
choke opening.  This increases emissions of  HC and CO  slightly
but decreases NO  (Ref. 27).  The relative increase in CO
                /\
emissions on catalyst-equipped vehicles is greater than  on
noncatalyst vehicles due to the relatively larger cold start
effect and the  lower emission standard.
1972-1974
1975
HC_
0. 1
0. 1
CO
0. 1
1.0
IYO.
0.0
0.0
          IJecel Val ve :  Defective decel valves cause an
increase in emissions of HC and CO during deceleration  (high
vacuum) conditions.   Since this defect affects only decelera-
tion conditions, the  effect on composite FTP emission is
relatively small.  The same emission increase factors assigned
to  idle stop solenoids and rich idle mixture adjustment were
assigned for the decel valve:
                         4-39

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                              HC        CO        N0_x
               1972-1974     0.1       1.0        0.0
                 1975        1.0       1.0        0.0

          Distributor Vacuum Deceleration Valve:  The distrib-
utor vacuum deceleration valve applies full  manifold vacuum
to the distributor during deceleration (high vacuum).  This
increases engine speed to improve combustion during the
deceleration period.   Failure of the valve causes full
vacuum advance at all times which will increase HC and NO
                                                         «
but reduce CO emissions (Ref. 3 and 27).   The following
emission increase factors were assigned:
1972-1974
1975
HC_
0. 1
0. 1
CO
0.0
0.0
N0y
A
2.0
2.0
          Distributor Starting Solenoid:  Failure of the
distributor starting solenoid causes hard cold starting and
prolonged cranking.  This may increase cold start emissions
due to flooding from excess gasoline.  The following emission
increase factors, therefore, were assigned on the basis of
engineering judgment:

1972-1974
1975
HC
1.0
1.0
cp_
1.0
1.0
--X
0.0
0.0
          JJiermal Vacuum Val ve:  The thermal vacuum valve or
switch is employed to switch spark advance from ported to
manifold vacuum.  When associated with EGR, TCS, SCS, CEC,
or OSAC systems, the TVS has been included in those categories
Failure of a TVS results in normal spark advance at all
temperatures.  Therefore, the  following emission increase
factors were assigned:
                         4-40

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1972-1974
1975
HC
0. 1
0. 1
CO
0.0
0.0
NO
— x
2.0
2.0
          Distributor Vacuum Valve:  Defective distributor
vacuum valves result in small  changes in spark advance
because the vacuum source is shifted between the EGR and
spark advance ports for improved driveabi1ity.  Therefore,
the following emission increase factors were assigned on the
basis of engineering judgment:
1972-1974
1975
HC_
0. 1
0. 1
co.
0.0
0.0
N0x
0. 1
0. 1
4.2.2     probability of Component Fai1ure Factor

          Each component category was assigned a factor
representing the probability of failure.   Supporting data
were either unavailable or contradictory.  Therefore, the
factors were assigned  based on the general  criteria dis-
cussed in paragraph 4.1.3.  The same probability factors
were assigned to similar components (i.e.; TVS, speed
sensors) even if they were used in different applications.
In determining the values for failure probability, considera-
tion was given to the following factors:

          •    Operating environment (temperature, gas
               characteri sti cs)
          •    Normal operating state ( acti vated , 'deacti vated )
          •    Operating principle (vacuum,  mechanical,
               electrical )
                         4-41

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4.2.2.1   Carburetion Systems

          Carburetor components and control devices are
generally quite reliable and are not usually reported as
defective during durability testing (Ref.  35,  47, 72 and 73).
In general, components operated mechanically or electrically
are more reliable than vacuum-operated devices (Ref. 3).
          The following electrically-operated  carburetor
components were, therefore, assigned a low probability of
failure (PF = 0.10) :

          •    Idle stop solenoid
          t    Throttle positioner
          •    Electric assist  choke heater
          •    Idle enrichment  system

          The following mechanical components  were assigned
a low probability of failure (PF=0.10) due to  their passive
function and low rate of deterioration.  The fuel filter is
a standard replacement part with recommended replacements
every 2 years.   These components are rarely, if ever,
associated with emissions failure in OEM installations
(Ref. 12, 16, 78, 94, 101 and 102):

          •    Metering jets
          •    Gaskets
          •    Fuel filter

          The following mechanical- or vacuum-activated
components were assigned a slightly higher probability of
failure (PF=0.30) because of repetitive cyclical operation
and sensitivity to adjustment:

          •    Throttle dashpot
          •    Metering rods
                         4-42

-------
          •    Choke mechanism
          •    Float and float valve
          •    Accelerator pump
          •    Power valve
          •    Vacuum break valve
          •    Staged choke pulldown

          The idle adjustment was assigned a high probability
of failure (PF=0.90) based on a 50,000-mile design life and
the expected degradation in carburetor idle air and fuel
flow rates (Ref.  2, 3,  27, 94, 98 and 99).

4.2.2.2   Ignition System

          Ignition system components, particularly spark
plugs and ignition wires, are closely related to emissions
and performance degradation.  Components known to be emissions
and performance-sensitive are routinely serviced or replaced
at intervals intended to occur before the expected failure.
In many cases, PVIM studies have shown that components which
appear marginal or defective actually have satisfactory
emissions (Ref. 12 and 94).
          The following primary ignition system components
were assigned a low probability of failure (PF=0.10) on the
basis of long design and service lives  (Ref. 70), and broad
performance tolerances before misfire actually occurs:

          •    Condenser
          •    Distributor mechanical advance
          0    Distributor drive mechanism
          •    Electronic ignition triggers
          t    Coils
          •    Ballast resistor
          •    Electronic ignition circuits
                         4-43

-------
          The following primary ignition system components
were assigned a slightly higher probability of failure (PF =
0.30) based on more rapid deterioration due to severe operat-
ing conditions.  These components ,. however , are designed to
last the certification period (Ref. 70):

          •    Ignition wi res
          t    Distributor cap and rotor
          •    Distributor vacuum advance diaphragms
          •    Dual diaphram vacuum advance mechanisms

          The following components were assigned a relatively
high probability of failure (PF=0.50) based on recommended
replacement intervals which are shorter than the certification
period:

          •    Points
          •    Spark delay valves

          The following components were assigned a relatively
higJi probability of failure (PF = 0.70) based on durability
data, garage experience and PVIM data.

          •    Spark plugs
          •    Basic timing adjustment

4.2.2.3   Air Induction System

          The air  induction system components are reliable
and durable.  With the exception of the air cleaner, all
components have design lives in excess of  50,000 miles.  The
air cleaner is routinely  replaced or  serviced several times
during  the certification  period.  Therefore, low probability
of  failure (PF=0.10) was  assigned  for the  air cleaner.
                         4-44

-------
          The  following  air induction components were assigned
a low probability of failure (PF=0.10) based on their
durabi1i ty :

          •     TAG shroud and hose
          •     TAG thermostat
          •     Turbochargers

          The  following  air induction components were assigned
a slightly higher probability of failure (PF=0.30) based on
more rapid deterioration due to repeated removal and recon-
nection or less durable  construction.

          •     TAG vacuum motor
          •     TAG vacuum hoses
          •     TAG fresh air inlet

4.2.2.4   Fuel Injection System

          The probability of failure of fuel injection
components was based on  a design life of 50,000 miles and
engineering  analysis of recommended maintenance practice and
system design.
          The following  mechanical components were assigned-
a very low probability of failure (PF=0.01) based on dura-
bility and broad tolerance of emissions to performance
variations :

          t    Accumulator
         " •    Fuel pump
          •    Fuel distribution manifold

          The following mechanical and/or electrical fuel
injection components were assigned a low probability of
failure (PF=0.30) based on adjustments or deterioration:
                         4-45

-------
          •    Pressure sensors/regulators
          •    Air sensors/switches
          •    Temperature sensors/switches
          •    Triggering switches
          •    Electronic fuel injection

          The following mechanical components were assigned
a moderate probability of failure (PF=0.50) on the basis of
the need for periodic adjustment or replacement due to
mechanical deterioration:

          •    Throttle valve(s)
          t    Inject ion valves
          ••    Solenoid injectors
          •    Starting valve
          •    Idle adjustment

4.2.2.5   Engine System

          The following engine components were assigned a
very low probability of failure (PF=0.01) since they should
last considerably beyond the certification period:

          •    Valve cam lobes
          •    Valve guides
          t    Piston rings
          •    Gaskets
          •    Camshafts

          A low probability of failure (PF= 0.10) was assigned
to failure of the valve, valve seat, and valve seals since
burned or leaking valves can be caused by numerous operating
conditions before 100,000 miles.
          A slightly higher probability of failure (PF=
0.30) is assigned to failure of the valve lifters and springs
                         4-46

-------
because of the need to periodically adjust some of these
valve mechanisms on some engines.

4.2.2.6   Emission Control  Systems

          The probability of failure of emission control
components depends on design life, typical maintenance
practice, and operating environment.  The following paragraphs
are devoted to discussions  of the  probability of failure of
specific component categories.
          PCV Valve, and Fresh  Air Filter - The PCV valve
and filter is replaced on most  engines every 2 years or
24,000 miles.  The replacement  is  designed to occur prior to
significant deterioration of the PCV system.  Therefore, a
low probability of failure  was  assigned (PF=0.30).
          PCV and Other Vacuum  Hoses - The PCV hoses and
other vacuum hoses are normally not serviced during the
certification period.  The  probable failure of these com-
ponents  is relatively low,  even over the life of the vehicle.
Therefore, the probability  of failure was defined (PF=
0.10).
          EVAP Canister - The carbon canister is replaced
during the certification period on some engines.  However,
on most  vehicles, the canister  is  not included in mandatory
replacement.  Activated carbon  is  durable, providing that it
is purged adequately and pore spaces are not clogged with
oil or particulates.  Therefore, a relatively low probability
of failure was assigned (PF=0.30).
          EVAP Fresh Air Filter, Control Valves, and Fuel
Tank Cap - These components of  the EVAP system are reliable
and have low probability of failure.  The filter is replaced,
usually  every 2 years or 24,000 miles, even on systems where
the carbon canister  is not replaced.  Therefore, a low
probability of failure was assigned for these components
(PF = 0. 10).
                         4-47

-------
          AI System - Components of the AI  system are rugged
and designed to be service free.  AI  failure is rarely
identified in surveillance or PVIM programs.  Therefore, a
low probability of failure is assigned to all  of the AI
system components (PF=0.10)  except for the  distribution
manifold and internal engine passages which were assigned
the lowest probability of failure (PF=0.01).
          EGR Valves, and Back Pressure Sensor - These two
components are exposed to particulates, water  vapor, acids,
and hot gases in the exhaust system.   They  are subject to
clogging, sticking, and corrosion.  These systems may be
visually inspected but are generally  not subject to perfor-
mance testing or mandatory replacement.  Therefore, a high
probability of failure was assigned to these components
(PF=0.70).
          Thermal Vacuum Valves, Vacuum Amplifier, Reducing
and Cjieck Val ves - These components are not serviceable and
not included in scheduled maintenance.  They are generally
reliable but are subject to sticking, diaphragm deteriora-
tion, and valve leakage.  These components  were assigned a
relatively low probability of failure (PF=0.30).
          Electrically-Operated Vacuum Solenoid Valves,
Seniors, and Electronic Components -  Vacuum solenoid valves
are used in various systems to regulate vacuum signals.
Various temperature, transmission, and speed sensors provide
signals to operate solenoid valves, status  lights, and
electronic control circuits.  Electrical components includ-
ing ESC electronic modules, time delay and  latching relays
are highly reliable and not subject to scheduled mainte-
nance.  These electrical and electronic components were
assigned a low probability of failure (PF=0.10).
          Catalyst (CAT) Canister Body and Supporting
She!1 - The structural part of  the catalyst is not subject
to deterioration except through physical damage.  A low
probability of failure was therefore  , assigned (PF = 0.01).

                          4-48

-------
          Catalyst Active Media - The catalyst active media
is subject to mechanical  and thermal  degradation.  The
probability of failure is relatively  high, particularly if
other malfunctions occur.  Therefore, a moderate probability
of failure was assigned (P F = 0. 5 0) .
          Heat Riser - The heat riser is exposed to hot,
corrosive, and particulate laden exhaust gases.   A relatively
high probability of failure was, therefore, assigned (PF=0.70)
          Decel  Valve - The decel valve is a relatively
reliable component once it has  been correctly adjusted.  No
maintenance is specified  and, therefore, a relatively low
probability of failure was assigned (PF=0.30).

4.2.3     Probability of  Repair Factor

          The factor representing the probability of repairing
a defective component was assigned  using the criteria defined
in paragraph 4.1.4.  The  probability  of repair was based on
the typical diagnostic and maintenance steps performed at
scheduled maintenance, and on the detectabi1ity of the
defect to the vehicle driver or mechanic.

4.2.3.1   Carburetion System

          Most carburetion-related  components, with the
exception of the fuel filter and idle adjustment, are not
included in scheduled maintenance.   Carburetor rebuilding is
usually performed when noticeable performance degradation
occurs which can be attributed  to leaking  or sticking compo-
nents.  Emission increases can  occur, however, before any
obvious performance deterioration becomes  apparent.
          The following carburetion system components do not
have a significant performance  impact, are not included in
normal scheduled or corrective  maintenance, and are expensive
to repair (Ref.  3).  They were, therefore, assigned a high
probability of no repair  (PF=0.90).

                         4-49

-------
          •    Metering jets
          •    Metering rods
          •    Choke
          t    Gaskets
          t    Float  and valve
          •    Idle enrichment system
          t    Vacuum break valves
          •    Power  valve
          t    Accelerator pump

          The following carburetion system components may
have a performance impact depending on the degree of failure
and compensating adjustments  made to idle speed and mixture.
These components are  also readily adjustable or replaceable
(Ref. 3 and 27).  They  were assigned a moderate probability
of no repair (PR=0.50).

          •    Idle stop solenoid
          •    Dashpot
          •    Throttle positioner

          The following carburetion components are usually
repaired during scheduled tune-ups.' Mechanics are familiar
with their replacement  and importance to good performance
(Ref. 3, 27, and 101).   They  were,  therefore, assigned a low
probability of no repair (PR=0.30).

          0    Idle adjustment
          o    Fuel filter

4.2.3.2   Ignition System

          Ignition system defects leading to misfire are
typically very noticeable and have a low probability of no
repair.  Basic ignition system maintenance is routinely

                         4-50

-------
performed including substantial preventive maintenance.
Some components, however, are expensive (distributors) and
may not be repaired due to consumer resistance until signifi-
cant performance deterioration has occurred (Ref. 3 and 27).
          The following ignition system components do not
have a significant performance effect and are not part of
normal ignition tune-up service; or, in the case of distributor
drives, are quite expensive (Ref..  3).  The probability of not
replacing these components was, therefore, quite high (PF=0.90).

          •    Di stri butor dri ve
          t    Spark delay valve
          •    Coils
          •    Ballast resistor

          The following components are not part of routine
tune-up practice, but have a significant performance impact.
They will probably be repaired if defective.   Therefore, a
moderate probability of no repair was assigned (PR=0.50).

          t    Mechanical advance
          •    Vacuum advance including dual  diaphragm
               di stri butors
          •    Ignition wires
          •    Distributor rotor
          •    Distributor cap

          The following components are included in routine
tune-up practice and/or they have a significant performance
impact.  They are expected to be replaced if defective
(Ref.  3 and 27).  Therefore, a low probability of no repair
was assigned (PR=0.10).

          •    Points
          t    Condenser.
                         4-51

-------
          •    Electronic ignition  trigger switches
          t    Spark plugs
          t    Electronic ignition  circuits
          •    Basic timing adjustment

4.2.3.3   Air Induction Systems

          The air induction system  regulates air flow into
the engine.  Physical  defects may be noticeable in external
components.  They may not be repaired, however, due  to
relatively small  performance degradation (Ref.  3).  Therefore,
the following components were assigned a high probability of
no repair (PR=0.90).

          «    TAG shroud and hose
          •    TAG thermostat
          •    TAG vacuum motor
          •    TAG vacuum hoses
          t    TAG fresh air inlet

          Turbochargers provide additional power and their
failure is readily detectable (Ref. 3).  They will probably
be repaired in order to regain lost performance.  Therefore,
a low probability of no repair is assigned (PR=0.30).
          The air filter is the only air induction component
on which maintenance (replacement)  is recommended and gener-
ally performed.  However, there is  no noticeable performance
degradation and the rate of deterioration  is low.  Therefore,
a moderate probability of no replacement was assigned for
air filters (PR=0.50).

4.2.3.4   Fuel Injection System

          Performance of the vehicle  is relatively insensitive
to defects in the fuel  injection system since most defects
                         4-52

-------
result in overfueling.   This is particularly true of mechani-
cal  fuel  injection systems.   Therefore, a high probability
of no repair (PR=0.90)  was assigned to the following components

          •    Accumulator
          •    Fuel  pressure sensors/regulators
          •    Throttle linkage and valve
          •    Injection valves
          •    Injectors
          •    Temperature sensors/switches
          t    Fuel  distribution manifold
          t    Starting valve.

          Several components can have significant effect on
the performance of electronic fuel  injection systems.  These
components regulate the timing and  quantity of fuel  delivered
to each cylinder.  Failure of the components may disable the
vehicle or significantly alter the  air fuel ratio over the
range of speed and load conditions.  These components were,
therefore, assigned a low probability of no repair (PR=0.10).

          •    Air sensors/switches
          •    Triggering switches
          •    Electronic fuel injection control circuits

          The idle adjustment on fuel injection systems is
similar to carburetion systems.  Therefore, the same proba-
bility of repair assigned to carburetor idle adjustment
(PR=0.30) was assigned to fuel injection idle adjustments.

4.2.3.5   Engine Systems

          The probability of repairing any engine system
during the certification period is  very low because of the
high expense and relatively small effect on performance from
                          4-53

-------
typical defects.  Therefore, the probability of no repair
assigned .to all engine system components was PR=0.90.
          The probability of adjusting valve lash or lifter
operation, however, is greater since this is recommended for
some 4-cylinder engines.  Therefore, the probability of
repair assigned to lifter/springs was PR=0.50.

4.2.3.6   Emission Control Systems

          The probability of repairing defective emission
control systems depends strongly on the performance effect
of the failure.  Unfortunately, most emission control compo-
nents do not have severe performance effects (i.e.; perfor-
mance and fuel economy may improve, or the performance
decrement is not detectable).  In addition, failure of these
components is relatively unusual and diagnostic procedures
are complicated.  Therefore, mechanics rarely attempt to
diagnose emission control system failures unless ignition
and carburetion components have been determined to be satis-
factory and performance is still poor.  Several exceptions
to the above comments do exist, however.  These are components
external to the engine which have specified maintenance
schedules and  include the PCV valve, EVAP canister, AI pump
and hoses and all vacuum lines.  These and other components
are discussed below.
          PCV Valve - The PCV valve can cause rough idle if
severely restricted (Ref. 3).  However, the PCV valve
is a scheduled maintenance component and subject to periodic
replacement during the certification period.  Therefore, a
relatively low probability of no repair was assigned (PR=0.30)
          PCV  Fresh Air Filter - The PCV air filter is not
normally serviced during the certification period, even
though it may  be recommended.  Failure of this component is
not likely to  be diagnosed due to the small performance
effect.  Therefore, a high probability of no repair was
assigned (PR = 0.70).
                         4-54

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          EVAP Canister and Fresh Air Filter - The EVAP
canister and its air filter do not have a noticeable perfor-
mance affect if defective.  However, the canister, or at
least the filter, is scheduled for periodic replacement.
Therefore, a moderate probability of no repair was assigned
(PR=0.50).
          PCV, EVAP, EGR. and Other Vacuum and Amplifier
Hoses - All  hoses providing vacuum signals can cause mani-
fold leaks if defective.  The vacuum leaks are likely to
cause intermittent misfire expecially at idle and during
deceleration.  The misfire is likely to be corrected because
of rough idle and vacuum hoses are an easy and inexpensive
component to replace.  Therefore, a relatively low proba-
bility of no repair was assigned to all vacuum hose defects.
(PR=0.50).
          EVAP Control Valves and Fuel  Tank Cap - Failure of
these components will have essentially  no performance affect
and cannot be readily diagnosed.  Therefore, a high proba-
bility of no repair was assigned (PR=0.90).
          AI Pump, jSelts and Hoses - Failure of these compo-
nents may create objectional noise leading to corrective
maintenance.  No vehicle performance degradation should be
noticed, however, unless a belt fails and disables some
other accessory.  Driveability of the vehicle should not be
affected, however.  Therefore, a high probability of no
repair was assigned (PR=0.70) to the belts, hoses and pump.
The AI manifold and injector nozzle, however, were very
unlikely to be repaired (PR=0.90) due to the fact that they
were integral to the engine.
          AI Check, Bypass and Diverter Valves - These
components will result in backfiring in the exhaust system,
if defective.  No other performance effect such as degraded
driveability should be noticed, however.  A moderate proba-
bility of no repair was, therefore, assigned (PR=0.50) since
the cost of replacing these components  is relatively low.
                          4-55

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          EGR Valves - EGR valve inspection is included in
most recommended maintenance schedules.  However, clogging
of the valve is likely to improve driveability so that there
is little incentive to diagnose and correct defective EGR
valves.  A high probability of no repair was,  therefore,
assigned (PR=0.70).
          £GR Back Pressure Valves - Back pressure valves
have been used for only two model-years.  No data is available
on their performance.  However, it is likely that they will
become clogged and inoperative.  Since they are not generally
included in the recommended maintenance schedules, it is  even
less likely that defects will be detected than in the EGR
valve  itself.  The probability of no -repair was therefore,
very high (PR = 0.90) .
          TJiermal Vacuum Valves, Vacuum Reducing and
Check  Valves - These valves regulate spark advance control
and EGR systems.  They are not included in recommended
scheduled maintenance.  Their failure is generally not
detectable and may improve driveability under some condi-
tions.  A high probability of no repair was therefore,
assigned (PR=0.90).
          Vacuum Solenoid Valves, Temperature, Transmission,
and Speed Switches and Relays - These components are not
included in recommended scheduled maintenance.  Failure is
also unlikely and may lead to improved driveability.  There-
fore,  the probability of no repair was quite high (PR=0.90).
          Catalyst (CAT) - Replacement of the catalyst,
either pellets or entire canister, is very unlikely due to
high cost and difficulty in diagnosing a failure with typical
garage instrumentation.  Therefore, a high probability of no
repair was assigned  (PR=0.90).
          H^eat Riser - A stuck heat riser valve may create
cold start problems.  However, service on it is difficult
due to its location  and may involve removal of the manifold.
Since  normal hot running of the engine is not degraded, it
                         4-56

-------
is very unlikely that corrective repair would be performed.
Therefore,  a high probability of no repair was assigned
(PR=0.90).
          Decel  Valve and Distributor Vacuum Deceleration
Va 1ve - The decel  valves regulate air fuel mixture during
deceleration.  Defects in these valves generally are not
detectable since they occur during deceleration.  Idle
performance can  also be compensated for by idle mixture or
speed adjustments.  Therefore, a high probability of no
repair was assigned (PR=0.90) to both components.
          Electric Assisted Choke - A defective electric
assisted choke will result in normal choke action and possibly
improved driveabi1ity .  Therefore, the probability of no
repair was very  high (PR=0.90).

4.2.4     Component Sales Volume

          Component sales data were not directly available
from industrial  or governmental sources.  This information
was, therefore,  estimated based on the following criteria:

          •    Sales or production volumeof each engine
               family.
          •    Cumulative scrappage of vehicles by model-
               year.
          •    Number of each component installed in a
               single unit from each engine family.
          •    Number of replacements of each component
               during the certification design life.

4.2.4.1   Sales  or Production Volume

          Sales  or production data were not available from
the manufacturers, the EPA, or published documents in detail
sufficient to precisely determine sales volume for this
study because component usage within certification familes
                         4-57

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varied depending on body style and accessory equipment.
Production data was provided by the EPA for some certification
families.  This data and published sales and production data
were used to estimate the sales volume for families where
data was missing.   The following approach was used:

          •    Engine families were defined on the basis of
               detailed component usage decribed in the
               Mitchell Manual Emission Control Service
               Manuals (Ref. 27).

          «    Components used only on one model or body
               style within an engine family were deleted
               unless that model or body style represented a
               significant application of the engine family's
               production.

          o    Sales of California configuration engine
               families were assumed to be 10 percent of
               each model's published production.

          ID    Published (Ref. 26) engine and transmission
               sales data by vehicle model were used to
               estimate the sales volume of engine families
               which were available in several vehicle
               models.

          Not all  engines and vehicle manufacturers were
included in the analysis.  Low production engine families
were deleted including most imported light-duty vehicles,
heavy-duty gasoline families, and most heavy-duty diesel
families.  Engine families which were deleted generally
used similar systems and components as those families which
were included.  Therefore ,vthe component usage data used in
the study was generally representative.  However, several
                         4-58

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gasoline engine families which were deleted used fuel injec-
tion systems.   This reduced the relative ranking of EFI
systems slightly.   The diesel  engine families which were
selected represented popular engines used in many different
trucks.  Component usage was not significantly different in
pre-1974 and post-1974 diesel  engine families.  Smoke emission
reductions were achieved primarily by cylinder geometry and
injector design modifications.  Therefore,  the relative
ranking of components were the same for both model-year
groups and not affected by deleting some families.

4.2.4.2   Scrappage Rate

          The  engine family production estimates were reduced
to reflect vehicle scrappage as of July, 1976.  Average
scrappage rates for each model-year were calculated from
published vehicle  registration data and applied to  all
vehicles in that model-year.  Unfortunately, published
registration data  was from 1 to 2 years late.  The  most
recent data available (Ref. 26) which was published in April
1976, contained complete registration data  only through the
1974 model-year.
          The  first interval with complete  data was for the
1973 model-year scrappage between 1974 and  1975.  This was
taken as the first model-year interval.  The second year
scrappage rate was determined from the reduction in 1972
model-year registration data between 1973 and 1975.  The
percent reductions were then plotted and a  smooth curve
drawn through  the  origin.  Scrappage rates  were then deter-
mined from the plot as shown in Table 4-4 for each  interval.
For this study, the average scrappage rate  was applied to
the production data assuming that 1976 was  the current year.
Therefore, the scrappage applied to each model-year was as
follows:
                         4-59

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                    Table 4-4.   SCRAPPAGE AS A FUNCTION OF VEHICLE AGE
MODEL
YEAR
1974
1973
1972
1971
1970
1969
1st FULL
YEAR
1975
1974
1973
1972
1971
1970
1st YEAR*
REGISTRATION
9,763
11,269
10,158
8,915
8,888
9,299
1975*
REGISTRATION
9,763
11,332
10,098
8,549
8,339
8,339
YEAR
INTERVAL
0
1
2
3
4
5
ACTUAL AVERAGE
SCRAPPAGE SCRAPPAGE
Percent Percent
0 0
0 0.5
0.59 2.0
4. 11 4.0
6.15 6.5
10.32 10.0
I
CT>
O
     *Registrations in thousands of vehicles

-------
     Model  Year:    1976    1975    1974    1973    1972
     Scrappage        0     0.5%    2.0%    4.0%    6.5%

4.2.4.3   Component Usage by Engine Family

          The component usage for each engine family was
obtained by reviewing the engine and emission control  system
descriptions contained in the Mitchell Emission Control
Service Manuals (Ref. 27):   The number of each component
category was recorded with  the following exceptions:

          •    Gaskets and  vacuum hoses were assigned  a  1 or
               0 to indicate presence or absence.  The
               actual number of individual components  on the
               vehicle was  not recorded.

          •    Engine mechanical components including  valves,
               valve lifters, spring guides, seals, and
               piston rings were set equal to the number of
               pistons although the actual number of indi-
               vidual component may have been greater.

4.2.4.4   Component Replacement by Engine Family

          The recommended frequency of replacement for each
component category was determined from maintenance schedules.
Only those  components with  mandatory replacement specified
were assigned a component replacement factor in the model.
The number  of replacements  was equal to the number of  times
a replacement was specified in 50,000 miles.  If replacement
was to be made every 6,000  miles, eight replacements were
assigned to that component/engine family.  Table 4-5 presents
typical component replacements although the individual
engine family component replacements may have differed
depending on model-year and manufacturer.
                         4-61

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Table 4-5.   TYPICAL COMPONENTS WITH DESIGN LIFE LESS THAN
50,000 MILES FOR WHICH 1 OR MORE REPLACEMENTS ARE SPECIFIED
COMPONENT NAME
Points
Condenser
Spark Plugs
Standard
High Energy
PCV Valve and
PCV Fresh Air Filter
EVAP Can and Carbon
EVAP Fresh Air Filter
Spark Delay Valve
Air Cleaner Element
Catalyst
PART
CODE
2.1
2.2
2.5
2.5.1
2.5.1
6.1.1
6.1.3
6.2. 1
6.2.3
2.3.7
3.2.0
6.9
TYPICAL
LIFE*
12,000
12,000

12,000
24,000
24,000
24,000
24,000
24,000
12,000
12,000
25,000
TYPICAL NUMBER
OF REPLACEMENTS*
4
4

4
2
2
2
2
2
4
4
1
 *Actual component life was reported by engine family.
                          4-62

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4.3       RANKING OF EMISSION-CRITICAL OEM COMPONENTS

          The rankings of emission-critical  components are
shown in Table 4-6 for the 1975 model-year and Table 4-7
for the 1972 through 1975 model-years.  These rankings are
abstracted from the tables shown in Appendix A.   Appendix A
contains detailed rankings, including the criticality index
values for early models only, late models only,  and all
models combined.  Tables 4-6 and 4-7 present independent
rank-ordered lists for HC, including evaporative emissions,
CO, NO , smoke, and a composite ranking based on the absolute
      A
value of the criticality indices regardless  of pollutant.
Component rankings, except for smoke, each include the 25
most critical components.  Smoke emissions were  dependent on
only 13 components identified in this study.  Therefore,
only those components are shown.
          In general, the order of the rankings  depended on
model-year although the same components ranked in the top 25.
Most components were critical to more than one pollutant,
although not necessarily to the same degree.  Critical
components for HC and CO typically included  the  following:

          t    Secondary ignition components such as spark
               plugs and wires, and distributor  cap and
               rotor.
          •    Cold start-related components such as choke,
               heat riser, and thermostatic  air  cleaner.
          •    Carburetion components affecting  off-idle
               operation such as power valve, metering rods,
               float and needle valve, and air cleaner
               element.
          t    Components which affect idle  air  fuel ratio
               such as adjustment screws, PCV valve and
               filter, and vacuum hoses which can cause
               intake mani fold 1eaks .
                         4-63

-------
                                 Table 4-6.  CRITICALITY INDEX RANKING - LATE MODELS*
                                (Automotive Parts Study - EPA Contract No.  68-01-1957)
             HC
                              CO
                              NO
                       SMOKE  (Diesel)
      COMPOSITE
cr>
-p.
Spark Plugs
Ignition Wires
CAT Active Media
Choke Mechanism
Power Valves
Heat Riser
EVAP Canister
Cap
Rotor
Idle Adjustment
TAC Vacuum Motor
TAC Vacuum Hoses
PCV Fresh Air Filter
PCV Valve
PCV Hoses
EVAP Hose
Valve Lifter/Spring
TAC Shroud
TAC Thermostat
Mag/Opt Triggers
EVAP Fresh Air
AI Pump/Belts
AI Hoses
Valve Seals
Exhaust Valves
Choke Mechanism
Power Valves
CAT Active Media
Metering Rods
Float and Valve
Vacuum Break Valve
Idle Adjustment
PCV Fresh/Air Filter
Air Cleaner Element
PCV Valve
AI Hoses
Spark Plugs
Vacuum Advance
AI Bypass Diverter
Valve Lifter/Spring
Ignition Wires
AI Pump/Belts
Valve Seals
Exhaust Valves
FI Starting Valve
Heat Riser
Mechanical Advance
Elec Assist Choke
AI Manifold
AI Check Valves
EGR Valves
EGR Thermo Valve
Thermo Vacuum Valve
EGR Vacuum Amplifier
Spark Delay Valve
EGR Hoses/Sea Is
Ignition Timing Adj
EGR Carb Spacer
EGR Backpress Sensor
.EGR Speed/Trans Sen
OSAC Vacuum Orifice
EGR Solenoid Valve
EGR Time Delay
ESC Speed Switch
TCS Temp Switch
TCS Vacuum Solenoid
TCS Trans Switch
TCS Thermo Valve
ESC Elec Module
TCS Time Delay
SCS Thermo Valve
EGR Temp Switch
SCS Vacuum Solenoid
SCS Speed Switch
EFI Trigger Switch
                                                                       Valve Lifter/Spring
                                                                       Valve Seals
                                                                       Exhaust  Valves
                                                                       MFI  Valves
                                                                       Air  Cleaner  Element
                                                                       Valve Cam Lobes
                                                                       Valve Guides
                                                                       Piston Rings
                                                                       FI Throttle  Valve
                                                                       FI  Idle  Adjustment
                                                                       Head Gaskets
                                                                       Camshafts
                                                                       FI Pressure  Sens/Reg
                                                                       Turbocharger
Spark Plugs
Ignition Wires
Choke Mechanism
Power Valve
Valve Lifter/Spring
EGR Valves
CAT Active Media
Valve Seals
Exhaust Valve
Metering Rods
EGR Thermo Vacuum
Float and Valve
Heat Riser
EVAP Canister
MFI Valves
Cap
Rotor
Thermo Vacuum Valve
Vacuum Break Valve
Idle Adjustment
TAC Vacuum Motor
TAC Vacuum Hoses
PCV Fresh Air Filter
Air Cleaner Element
EGR Vacuum Amplifier
      *Late models for HC, CO, and NOX include 1975 and subsequent model  years.
       Late models for smoke include 1974 and subsequent model  years

-------
                           Table  4-7.   CRITICALITY  INDEX RANKING - ALL 1972 AND LATER MODELS
                                (Automotive  Parts Study - EPA Contract No. 68-01-1957)
             HC
                              CO
                              NO
                     SMOKE (Diesel)
                             COMPOSITE
CT>
Ul
Spark Plugs
Ignition Wires
Valve Lifter/Springs
Choke Mechanism
Power Valves
Valve Seals
Exhaust Valves
Rotor
Cap
CAT Active Media
EVAP Canister
Heat Riser
Points
Idle Adjustment
TAG Vacuum Motor
TAC Vacuum Hoses
Coil
Ballast Resistor
PCV Valve
PCV Fresh Air Filter
PCV Hoses
EVAP Hoses
Valve Cam Lobes
Valve Guides
Piston Rings
Choke Mechanism
Power Valves
Valve Lifter/Springs
Float and Valve
Valve Seals
Exhaust Valves
Metering Rods
Air Cleaner Element
PCV Fresh Air Filter
Idle Adjustment
CAT Active Media
PCV Fresh Air Filter
Vacuum Break Valve
AI Hoses
Valve Cam Lobes
Valve Guides
Piston Rings
Vacuum Advance
AI Pump/Belts
Idle Stop Solenoid
Spark Plugs
AI Bypass/Diverter
Accelerator Pump
Ignition Wires
Metering Jets
EGR Valves
EGR Thermo Valva
Spark Delay Valve
EGR Vacuum Amplifier
Thermal Vacuum Valve
EGR Hoses/Seals
TCS Temp Switch
Ignition Timing Adj
TCS Trans Switch
TCS Vacuum Solenoid
EGR Solenoid Valve
TCS Time Delay
OSAC Vacuum Orifice
EGR Carb Spacer
EGR Backpress Sensor
TCS Thermal Valve
EGR Time Delay
EGR Temp Switch
EGR Speed/Trans Sw
OSAC Vacuum Bypass
ESC Speed Switch
ESC Elec Module
ESC Vacuum Valves
ESC Temp Switch
Dist Vac Decel Valve
MFI Valves
Valve Lifter/Springs
FI Throttle Valve
FI Idle Adjustment
Valve Seals
Exhaust Valves
FI Pres Sens/Reg
Air Cleaner Element
Valve Cam Lobes
Valve Guides
Piston Rings
Head Gaskets
Camshafts
Turbocharger
Spark Plugs
Ignition Wires
Choke Mechanism
Power Valves
MFI Valves
Valve Lifter/Springs
EGR Valve
Float and Valve
Exhaust Valves
Valve Seals
Metering Rods
EGR Thermal Valve
Air Cleaner Element
PCV Valve
Rotor
Cap
Idle Adjustment
Spark Delay Valve
CAT Active Media
PCV Fresh Air Filter
EVAP Canister
Heat Riser
FI Throttle Valve
FI Idle Adjustment
EGR Vacuum Amplifier

-------
          t    Emission control  components  such as  catalyst
               and air injection components.

          Emissions of NO  were  dependent on  the performance
                         A
of NO  control  systems, including the EGR valve and control
     /\
components, and ignition advance control  components such as
vacuum advance  units, delay valves, distributor components,
TCS components, and carburetion  components  which can create
lean operation.
          Smoke emissions were related to 13  basic  engine
components on diesel  engines.   These components included
engine valves and valve train  components, piston rings, air
cleaner, and fuel injection valves and control  equipment.
          Some  components can  cause emissions failures
but were not ranked in the top 25 critical  components.
Table 4-8 summarizes  those components which were found to
cause a failure of one or more emission standard.   This list
includes those  components shown  in Table  3-1  and Appendix B
for which one or more emission increase factor  had  a value
of at least 1.0.  As  can be seen from Table 4-8, most of the
components would result in a failure of one or  more standards
i f defecti ve.
                         4-66

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Table 4-8.   OEM COMPONENTS WHICH CAN
      CAUSE AN EMISSION FAILURE
PART OR COMPONENT
Carburetor System
Idle Stop Solenoid
Throttle Dashpot
Throttle Positioner
Metering Jets
Metering Rods
Vacuum Break Valves
Choke Mechanism
Power Valves
Float and Valve
Idle Adjustment
Heat Riser
Idle Enrichment System
Electric Assisted Choke
Staged Choke Pulldown
Ignition System
Points
Condenser/Capacitor
Distributor Cap
Distributor Rotor
Mechanical Advance Mechanism
Vacuum Advance Mechanism
Distributor Drive Mechanism
Magnetic or Optical Triggers
Spark Plugs
Ignition Wi res
Coil - Inducti ve
Bal 1 ast Resi stor
Ignition Timing Adjustment
Spark Delay Valve
Air Induction System
Thermostatically-Controlled
Air Inlet
Vacuum Motor and Hoses
Air Cleaner Element
Turbochargers
EMISSIONS FAILURE
HC

X





X
X

X
X
X
X
X

X
X
X
X


X
X
X
X
X
X




X
X
X

CO

X
X
X
X
X
X
X
X
X
X
X
X
X
X





X
X












X

NOX




























X
X






Smoke


































X
X
                 4-67

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Table 4-8.   OEM COMPONENTS WHICH CAN
CAUSE AN EMISSION FAILURE (Continued)
PART OR COMPONENT
Fuel Injection System
Fuel Pressure Sensors/Regulators
Throttle Linkage and Valve
Injection Valves
Air Sensors/ Switches
Temperature Sensors/Switches
Injectors
Triggering Switches
Starting Valve
Idle Adjustment Screws
Engine System
Valve Lifters and Springs
Cams
Valves, Guides and Seats
Seal s
Ri ngs
Gaskets
Camshafts
Emission Control System
PCV Valve
PCV. Hoses
PCV Fresh Air Filter
A I Distribution Manifold
AI Hoses
AI Inlet Filter
AI Check Valves
AI Bypass/Di verter Valves
AI Gulp Valves
AI Pump
EVAP Canister Body and Carbon Media
EVAP Hoses
EVAP Fresh Air Filter
EVAP Vapor/Liquid Separator
EVAP System Vapor Control Valves
EVAP Fuel Tank Cap
EGR Valves or Orifices
EGR Hoses , Gaskets , Seals
EGR Temperature-Controlled Valve
EGR Solenoid-Controlled Valve
EMISSIONS FAILURE
HC




X
X

X
X
X

X
X
X
X
X
X
X

X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X




CO

X


X
X
X

X
X

X
X
X
X
X
X
X

X

X
X
X
X
X
X
X
X










NOX



































X
X
X
X
Smoke

X
X
X







X
X
X
X
X
X
X





















                 4-68

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Table 4-8.   OEM COMPONENTS WHICH CAN
CAUSE AN EMISSION FAILURE (Continued)
PART OR COMPONENT
Emission Control System (Cont'd)
EGR Temperature Switch
EGR Speed/Transmission Switch
EGR Time Delay Control
EGR Vacuum Amplifier
EGR Vacuum Reducing Valve
EGR Carburetor Spacer
EGR Back Pressure Sensor
EGR Check Valve
TCS Vacuum Solenoid
TCS Vacuum Lines and Hoses
TCS Time Delay Control
TCS CEC Valve
TCS Temperature Control Valve
TCS Transmission Switch
TCS Reversing Relay
SCS Vacuum Solenoid
SCS Vacuum Lines
SCS Time Delay Control
SCS Speed Sensing Switch
SCS Temperature-Control 1 ed Valve
OSAC Vacuum Orifice Valve
OSAC Vacuum Hoses
OSAC Thermal Valve
OSAC Vacuum Bypass Valve
OSAC Temperature Sensor
ESC Electronic Module
ESC Hoses
ESC Vacuum Val ves
ESC Temperature Sensing
ESC Speed Sensing Switch
CAT Body
CAT Active Media
Heat Ri ser
Decel Valve
Distributor Vacuum Deceleration Val-ve
Distributor Starting Solenoid
Thermal Vacuum Val ve
EMISSIONS FAILURE
HC











X
X



















X
X
X

X

CO










X

X




X




X




X



X
X

X

X

NO
X

X
X
X
X
X
X
X
X
X
X
X

X
X
X
X

X
X
X
X

X
X
X
X

X
X
X




X

X
Smoke






































                 4-69

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                       Section 5

                  SYMPTOMS OF FAILURE
          This section describes the characteristic symptoms
of failure for each of the emission-critical  components
listed in Section 4 for late-model; i.e., post-1975 model-
year vehicles.  Symptoms of component failure involve the
owner's or driver's ability to detect whether a defect is
present and the mechanic's ability to diagnose and correct
it.  In general, the driver is sensitive to certain perfor-
mance criteria.  Some owners or drivers may also be sensitive
to changes in fuel  economy, although emissions degradation
can occur without noticeable loss in fuel economy.  A few
catalyst-equipped vehicles have warning lights to indicate
abnormally high catalyst temperatures.   While they do not
identify the defect, they do indicate that a  defect (typically
misfire) does exist.  In general, the detectabi1ity of a
component's failure depends on its affect on  one or more of
the following performance characteristics:

          •    Hard starting.
          •    Rough idle and stalling.
          •    Poor driveability expressed by stumble,
               surge, hesitation, and poor acceleration.
          •    Pinging, knock, or backfiring.
          •    Poor fuel economy.
          •    Excess smoke.
                          5-1

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          A component may, of course, cause more than one
symptom.   Many components can cause the same symptom.
Therefore, the presence of a symptom does not necessarily
indicate  a specific defective component.  Table 5-1 lists
many typical  performance characteristics and the defects
which can cause them (Ref. 3).
          All  component defects can be diagnosed and corrected
if sufficient  time and effort is expended.   However, defects
which do  not  degrade performance are unlikely to be serviced
even if they  are included in scheduled maintenance.  In
addition, all  components affecting cold start performance
are unlikely  to be serviced since mechanics generally do not
and cannot diagnose or service  vehicles that are running
cold.  Diagnosis of the failure is required since many
different component defects cause similar symptoms.  Many
garages,  however, routinely perform ignition system tune-up
(plugs, points, rotor, carburetor and timing adjustments)
first and then attempt to diagnose any remaining performance
defects.
          The  following discussion of symptoms of failure
will be presented in the following order for those components
found to  be critical to HC, CO, NO  or smoke emissions:
                                  A

          •    Carburetion components
          •    Ignition system  components
          t    Air induction components
          •    Fuel injection components
          •    Mechanical components
          •    Emissions control components

Table 5-2 summarizes the symptoms of failure for the emission-
critical  components and systems.
                          5-2

-------
Table 5-1.  POSSIBLE CAUSES OF COMMON PERFORMANCE PROBLEMS
                  (ABSTRACTED FROM REF.  3)
POSSIBLE CAUSE
1. Weak battery '
2. Corroded or loose battery connections
3. Loose ground connections for battery and/or engine
4. Faulty starter or solenoid
5. Moisture on ignition cables and distributor cap
6. Faulty ignition cables
7. Faulty coil
8. Incorrect spark plug gap or dirty plugs
9. Incorrect ignition timing
10. Dirt or water in fuel line or carburetor
11. Carburetor flooded
12. Incorrect carburetor float setting
13. Faulty fuel pump
14. Carburetor precolating (vapor lock)
15. Sticking choke
16. Defective neutral starting switch
17. Defective ignition switch
18. Air cleaner obstructed
19. Faulty emission control units
20. Faulty ignition distributor
21. Idle speed set too low
22. Incorrect choke adjustment
23. Idle mixture too lean or too rich
24. Intake manifold leak
25. Worn distributor rotor
26. Incorrect valve lash (mechanical lifters)
27. Carburetor float needle valve inoperative
28. Choke defective or incorrectly set
29. Blown cylinder head gasket
30. Leaking engine valves
PERFORMANCE PROBLEMS
Hard
Starting
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X










Engine
Stalls


X
-
X
X
X




X








X
X
X
X
X
X
X
X


Power
Loss







X
X
X

X
X




X
X



X

X
X


X
X
Poor
Acceleration






X
X
X
X












X






X
High Speed
Miss






X
X
X
X









X




X
X



X
Noise
Dieseling


















X












-------
Table 5-1.  POSSIBLE CAUSES OF COMMON PERFORMANCE PROBLEMS (Continued)
                       (ABSTRACTED FROM REF.  3)
POSSIBLE CAUSE
31. Restricted exhaust system
32. Weak valve springs
33. Defective accelerator pump
34. Sticking engine valves
35. Faulty condenser
36. Clogged carburetor jets
37. Worn valve lifter
38. Worn cams
39. Worn valve guides
40. Incorrect spark plug type
41. Combustion chamber deposits
42. High idle speed
PERFORMANCE PROBLEMS
Hard
Starting












Engine
Stalls












Power
Loss
X
X










Poor
Acceleration

X
X
X








High Speed
Miss



X
X
X
X
X
X



Noise
Diesel inq









X
X
X

-------
                                        Table 5-2.  SYMPTOMS OF COMPONENT FAILURE
DEFECTIVE COMPONENTS
Carburetion System
Choke Components
Metering Rods
Float and Valve
Power Valve
Electric Assist Choke
Idle Adjustment
Vacuum Break Valve
Ignition System
Plugs/Wires
. Cap/Rotor
Electronic Triggers
Timing Adjustment
Advance Mechanisms
Air Induction System
TAC Components
Air Cleaner
Vacuum Hose Leaks
Turbocharger
CRITICAL POLLUTANT
HC

X


X

X


X
X
X



X

X

CO

X
X
X
X
X
X
X

X



X


X


N0x












X






Smoke


















X
SYMPTOM OF FAILURE
Hard
Starting

X

X
X




X
X
X



X



Drive-
abi lity

X
X
X
X




X
X
X
X
X



X
X
Rough
Idle



X


X
X

X
X
X



X

X

Fuel
Economy

X
X
X
X

X


X


X
X


X

X
Back-
Firing



















en
i
en

-------
                                  Table 5-2.   SYMPTOMS  OF  COMPONENT FAILURE (Continued)
DEFECTIVE COMPONENTS
Fuel Injection System
EFI Trigger Switch
EFI Starting Valves
Injection Valves
Pressure Reg/Sensors
Mechanical System
Valve Components
Rings
Gaskets
Emission Control System
Catalyst
PCV Components
EGR Components
EVAP Components
AI Components
Heat Riser
TCS/SCS Components
Spark Delay Valves
Thermal Vac Switches
CRITICAL POLLUTANT
HC






X



X
X

X
X
X



CO


X



X



X
X


X
X



N0x

X










X



X
X
X
Smoke



X
X

X
X
X










SYMPTOM OF FAILURE
Hard
Starting

X

X











X



Drive-
ability

X
X
X
X

X
X
X






X



Rough
Idle

X

X


X
X
X


X
X
X
X
X



Fuel
Economy

X
X
X
X

X
X
X










Back-
Firing

X
X











X




en
en

-------
5.1       CARBURETION COMPONENTS

          In general, the carburetion system components
which have significant impact on emissions do not have
significant performance symptoms.  Exceptions to this are
carburetor defects which result in lean misfire which can
create noticeable performance deterioration.  Improper
adjustment or failure of the accelerator pump, power valve,
float, metering rods or idle adjustment can result in
mixture lean-out during acceleration and resulting stumble,
surging, and hesitation.  The choke can also cause lean
misfire and detectable driveability degradation if it fails
to come on during cold starts.  However, this is not a
frequent choke failure mode compared to sticking closed or
failing to open rapidly or fully.  Typical failure modes for
the other components also tend to produce rich operation
rather than lean operation.
          The carburetion components which ranked high in
criticality included the following:

          •    Choke mechanism
          •    Power valves
          •    Float and valve
          •    Metering rods
          «    Vacuum break valves
          •    Idle adjustment
          •    Electric assist choke

          The above components have failure modes which
produce rich operation and, consequently, they are critical
to HC and CO emissions.  The failures  (except delayed warm-
up) would probably be detected by emissions inspection.
However, performance degradation would not be noticeable
since engines are presently designed to operate near the
lean  combustion limit.  Consequently,  engines can tolerate
                          5-7

-------
significant mixture enrichment before any performance degra-
dation, resulting from rich misfire, is detected.
          Carburetor problems are generally subtle and may
be difficult to isolate.   Carburetor rebuilding is also
fairly time-consuming.  Many garages do not attempt to
repair carburetors and instead recommend that a replacement
(either new or rebuilt) carburetor be installed.   Exceptions
to the above are the choke, throttle linkage, and  idle
mixture adjustments which are easy to perform and  do hot
require removing or disassembling the carburetor.
          Diagnosis of carburetor malfunctions is  most
effectively accomplished  by using a dynamometer and infrared
analyzer to determine the modal  failures.  This is helpful
in determining whether the accelerator pump, power valve,
metering jet, float level, or choke is defective.   However,
few garages use dynamometers and only some have exhaust gas
analyzers.  Typical diagnostic procedures involve  first
repairing or verifying correct performance of the  ignition
system and then checking  carburetor adjustments to specifica-
tions.  Typical components which may be incorrectly adjusted
or worn include float, metering  rod, accelerator  pump,
power valve, metering jets, gaskets, choke, throttle dash-
pot, throttle positioner, idle-speed and mixture  screws.
5.2       IGNITION SYSTEM COMPONENTS

          Ignition system components are typically critical
to HC emissions, although some component failures also can
increase CO or NO  emissions.  Ignition failures are the
                 /\
most readily detected defect due to engine vibration or
bouncing which occurs when a cylinder misfires.   Ignition
misfires cause momentary power loss which can be detected as
rough running.  A defective ignition system can  also cause
hard starting and stalling.  Ignition misfire usually becomes
                          5-8

-------
more severe under load since the entire ignition system is
stressed more than at idle.   However, cruise misfire is more
difficult to detect since the higher engine speed smooths
out engine vibration and bounce.  Misfire usually develops
gradually.  Therefore, it may be difficult to detect inter-
mittent misfire until it becomes rather frequent.  The
following ignition components create similar symptoms of
failure, including poor acceleration, stumble, and rough
running:

          •    Spark plugs
          •    Ignition wires
          •    Rotor
          •    Cap
          t    Electronic ignition triggers

          Advanced ignition  timing is emission-critical for
NO    Unfortunately, timing  defects are difficult to detect
  A
unless they become very severe.  Advanced basic timing can
cause pinging or knock.  Retarded timing can decrease fuel
economy and acceleration performance.  Vacuum and mechanical
advance failures have the same general  effect as retarding
the basic timing and are critical to CO emi-ssions.  Therefore,
the same level of detectabi1ity applies to advance failures
as applies to incorrect basic timing.
          Routine ignition tune-up is the "bread and butter"
of the automotive repair industry.  The ignition system is
the easiest to diagnose and  the one most effectively repaired.
Most garages have ignition analyzers and scopes with which
to diagnose and isolate defects.  These instruments provide
a means of determining whether a single plug is misfiring,
whether ignition cables are  grounded or open, whether the
coil is defective or whether the points (if equipped) are
burned, pitted or improperly adjusted.   The mechanic, unfortu-
nately, does not have a means to simulate high load unless
                          5-9

-------
he has a dynamometer.   Many mechanics, however, road test
vehicles, particularly in response to specific owner com-
plaints.  The road test enables the mechanic to isolate
specific modal  failures which may indicate carburetion or
ignition defects.
5.3       AIR INDUCTION COMPONENTS

          The air induction system components which were
emission-critical included the thermostatic air cleaner
(TAG), air cleaner element, and turbocharger (diesel).   The
TAC components influence the rate of engine warm-up and
smoothness of the cold idle.  Defects in the TAC which  also
create vacuum leaks may result in lean misfire at idle.
This would be detected as a rough idle with a tendency  to
stall even when hot.  TAC components were critical to HC
emissions due to lean misfire.
          The air cleaner element does not have a performance
or driveability impact.  Routine service practice includes
preventative replacement of the air cleaner whenever it
appears dirty, even though emissions may not be adversely
affected.  Severely restricted air cleaners can increase
fuel consumption.  The increase, however, is not likely to
be detected by the average motorist.  Air cleaner testers
are available.  However, recent data indicate that visual
inspection is probably satisfactory since 75 percent restric-
tion may be required before a significant HC or CO emission
increase occurs (Ref. 94 and  100).
          A defective turbocharger produces a loss of power
and increased fuel consumption (Ref. 63 and 67).  These two
factors are probably apparent to owners and drivers, parti-
cularly, if the vehicle is operated frequently near its
maximum power rating where the turbocharger is most effective
                          5-10

-------
5.4       FUEL INJECTION COMPONENTS

          Mechanical fuel  injection components were critical
only to smoke emissions.  The performance symptom of failure
is primarily decreased fuel  economy.  The characteristic
defect of the emission-critical  fuel injection components
all produce rich mixtures.  Since these components are used
in diesel engines, increased smoke emissions would be a
detectable symptom.
          Electronic fuel  injection starting valves and
triggering switches were emission-critical to CO and NO ,
                                                       ^
respectively.  A defective starting valve is probably not
detectable by the driver unless  it fails to operate causing
hard starting.  The more critical failure mode is for it to
remain operating at all times causing mixture enrichment.
Defective triggering switches, however, will lead to lean
mixtures and possible misfire.  This will probably be detected
by the driver.
          Diagnosis of the fuel  injection system defects
involves verification of adjustments of the fuel pressure
and throttle or injection  valve  operation.  Electronic fuel
injection components can be  checked for continuity and
specified resistance.
5.5       MECHANICAL COMPONENTS

          Emission-critical mechanical components included
valves and valve train, piston rings, and head gaskets.
Defects in the valves may be detected by a misfire at  idle,
loss of power and acceleration or by engine noise.  Some
engines may develop noise if the valve lifters or lash are
improperly adjusted.  The symptom of misfire due to leaky
exhaust valves is difficult to distinguish from ignition
misfire, however, unless specific diagnostic procedures are
followed.
                          5-11

-------
          Piston rings may be defective in addition to, or
instead of, the exhaust valves.   This failure can be detected
by specific diagnostic procedures but, generally, cannot be
distinguished from defective valves by the owner.  Defective
rings may cause excess blowby or excess oil consumption
depending on the ring which fails.   If excess oil consumption
occurs, the defective rings may  be  detected by the owner or
driver.
          Defective head gaskets may cause oil or water to
enter the cylinder.  The head gasket defects cannot be
distinguished by the owner or driver from other mechanical
or ignition defects which cause  similar performance
degradation.
5.6       EMISSION CONTROL COMPONENTS

          Most of. the emission control components were found
to be emission-critical.  These components are discussed in
the fol1owi ng order:

          •     PCV system
          •     EVAP system
          •     Air injection system
          •     EGR system
          •     TCS system
          t     SCS system
          •     ESC system
          •     OSAC system
          •     Catalyst
          •     Thermal vacuum valves
          t     Electric assist choke
          •     Heat riser
                          5-12

-------
          Most emission control  system components do not
usually provide obvious performance degradation to indicate
that they have failed.
          Diagnosis of  emission  control  defects is normally
performed after conventional  engine, ignition, or carburetion
failures have been corrected.   This diagnosis involves
functional  tests of electrical,  mechanical  and vacuum compo-
nents.   Failures which  cause  vacuum leaks (i.e., vacuum
hoses and amplifiers),  however,  may produce lean misfire at
idle which  would be detected  as  rough idle  and possible
stalling.

5.6.1     PCV System

          The PCV valve and hoses may result in rough idle
due to  slow engine speed if they become  sufficiently clogged.
The PCV system is tested for  vacuum and  flow rate to verify
free flow.   The PCV valve is  also a standard replacement
component and is frequently replaced as  a preventative
repai r.

5.6.2     EVAP System

          The EVAP system does not have  obvious failure
symptoms and cannot be  readily diagnosed except to verify
that vapor hoses and vacuum lines are tight.  The EVAP fresh
air filter is replaced  periodically and  should be replaced
if dirty.  The EVAP system can produce excessive air flow if
the check valve sticks  open.   This gives the symptom of a
vacuum leak and will probably be compensated by enrichening
the idle mixture or increasing the idle  speed.  Diagnosis of
a stuck check valve is  performed by listening for valve
action as vacuum is applied and removed.
                          5-13

-------
5.6.3     Air Injecti on System

          The air injection system components may create
unusual  noise either in the affected component (i.e., belt
or pump), or backfiring as a result of failure of the diverter
or bypass valves. Air injection system diagnosis is performed
by checking for correct component function.  The air pump
function is checked by applying vacuum to the bypass valve
and listening for the air discharge.  The check valve can be
inspected by attempting to blow through it.

5.6.4     E_GR and Timing Modulation Systems

          Components affecting EGR or vacuum advance (TCS,
SCS, ESC, OSAC) generally fail in a manner which provides
equal or better performance than when the components are
functioning.   This is because normal advance signals are
provided at all times when the components fail.  Normal
advance usually provides better part-throttle acceleration
than retarded advance.  Similarly, defective EGR components
will disable the EGR system, resulting in less hesitation
and stumble than may occur with EGR.
          The EGR valve and vacuum control valves can be
tested by observing valve operation when vacuum is applied.
The valve may be removed for visual inspection if a defect
is suspected and the valve diaphragm is operating.  The
valve can then be tested to ensure that it is not clogged.
          The electrically-operated components of the TCS,
SCS, and ESC systems can be checked by making electrical
tests of continuity and resistance at specified test points.
The vacuum control devices can be checked to ensure that
valves open and close properly or delay vacuum changes  the
specified amount.  These components regulate vacuum advance
under specified conditions.  Overall, system function can be
                          5-14

-------
determined by measuring total  advance under various trans-
mission and rear wheel conditions.   The vehicle can be
tested by raising the rear wheels off the ground and running
at several unloaded speeds.

5.6.5     Catalyst Systems

          Impending catalyst failure or failure of other
components resulting in over-temperature of the catalyst is
indicated by the catalyst warning light provided on some
vehicles.  This warning informs the driver that a defect
condition exists which requires corrective action but does
not define the defect.  A defective catalyst., however, does
not degrade performance and will usually not show an over-
temperature warning since the activity of the catalyst will
be depressed.
          The catalyst cannot be directly tested without
performing emissions measurements.   However, a defective
catalyst may provi.de low idle and 2,500 rpm readings if the
basic idle mixture is lean, there are no other ignition or
carburetion defects present, or the vehicle is equipped with
air injection.  A quick diagnostic test is to pull a plug
wire and allow misfire on one cylinder to occur for a few
minutes.  A defective catalyst will result in 1,500 to
2,000 ppm HC emissions at idle.  A functioning catalyst will
reduce this to several hundred ppm HC .

5.6.6     Thermal Vacuum Valves

          Thermal vacuum valves are usually included, in
timing modulation or EGR systems to regulate their performance
according to engine temperature.  Failure of these valves
will have no appreciable effect on vehicle performance since
normal spark advance and no EGR will  usually be provided.
                         5-15

-------
          Thermal  vacuum valve function can be checked when
the fluid temperature is known.  This can be done by measuring
the coolant temperature, if convenient, or by removing the
valve and placing  it in water known to be cold (ice) and hot
(boiling).  Thermal  vacuum valves also have a nominal position
at normal engine temperatures.  This position can be tested
by checking for flow or vacuum through the nominally open
path.  Some manufacturers specify a functional check using
engine rpm in response to changes in vacuum advance.

5.6.7     Electric Assist Choke
          Defective electric assist chokes do not affect
performance since normal thermostatic choke opening occurs.
This provides slightly longer choke operation, richer mixture
and smoother engine operation.  Providing that other defects
are not also present, the small  increase in choke operation
will have no effect on fuel  economy.  The electric assist
choke heater can be tested for continuity and specified
current flow.  A defective electric assist choke will either
produce no current flow at normal  ambient conditions or
nominal current flow at low temperature.

5.6.8     Heat Riser

          A stuck heat riser will  affect cold idling and
acceleration because hot gases are not provided to promote
rapid warm-up and vaporization of the fuel.  This causes
misfire which is detected as rough idle, hesitation, and
stumble until the intake manifold is heated by conduction
from the engine block.  The heat riser can be mechanically
tested to verify free movement.   A free heat riser will
generally operate correctly.  A frozen heat riser will
generally be stuck open causing a rough cold idle and delayed
warm-up.
                         5-16

-------
                       Section 6

                  RECOMMENDED TESTING
          Components that were recommended for testing are
discussed in this section.  No heavy-duty diesel  components
were recommended due to the relatively low criticality of
smoke-related components compared to the gaseous  pollutants.
The 25 original equipment (OEM) components selected for
testing are discussed in paragraph 6.1.  The test protocol
recommended for the 25 OEM components is discussed in
paragraph 6.2.
6.1       SELECTION OF COMPONENTS

          The components selected for testing included
fundamental ignition and carburetion components which affect
vehicle performance and emissions.  Data on some of these
components have been reported in the literature.  However,
controlled experiments on catalyst-equipped vehicles were
not reported for most of these components.  Other components
recommended for testing may be included in on-going or
planned restorative maintenance and characterization programs
and, therefore, may be subsequently deleted.  Some of the
recommended components do not have obvious symptoms of
failure but their impact on emissions is critical enough to
warrant inclusion in the Phase III test program.  Other
components were not well documented in the literature and
the Phase III testing provides an opportunity to obtain
these data.
                          6-1

-------
          Table 6-1 summarizes the components selected for
testing and the suggested functional  range over which they
should be tested.   Several  components have more than one
basic operating design.   One each of  these multiple configur
at ions is suggested where appropriate.

6.1.1     Carburetion System Components

          The following  six carburetion  components  were
recommended for testing  on  both air injection and nonair
injection-equipped vehicles.

          t    Choke
          •    Float and valve
          t    Power valves
          t    Idle adjustment
          •    Metering  rods
          •    Vacuum break valve

The other major carburetor  components (gaskets, accelerator
pump, throttle positioners, dashpots, and  metering  jets) are
not recommended for testing due to their low  criticality as
OEM components.

6.1.1.1   Choke

          The choke has  several failure  modes.   Adjustment
of the thermostat  or choke  linkage may  be  incorrect.  The
operating linkage  may be bent or stuck  preventing choke
opening.   The thermostat or electric  assist heater  may be
defective resulting in delayed choke  opening.  Two  choke
defects are, therefore,  selected for  testing:

          •    Choke plate  stuck closed
          •    Choke thermostat set two  index marks rich
               (delayed  opening)
                          6-2

-------
                              Table 6-1.  COMPONENTS RECOMMENDED FOR TESTING
        COMPONENT
                DEFEC1
        VARIABLE RANGE
Carburetion System
  1.  Choke
  2.  Float and Valve
  3.  Power Valve
  4.  Idle Adjustment
  5.  Metering Rod
  6.  Vacuum Break Valve

Ignition System
  1.  Spark Plugs
  2.  Wires
  3.  Cap
  4.  Rotor
  5.  Vacuum Advance
  6.  El Mag Trigger
  7.  Basic Timing

Air Induction System
  1.  Thermal Air Inlet

Mechanical System
  1.  Valve Adjustment
  2.  Exhaust Valve

Emission Control System
  1.  Heat Riser
  2.  Catalyst
  3.  Air Injection System
  4.  PCV Valve
  5.  Spark Delay Valve
  6.  EGR Valve
  7.  Backpressure Sensor
  8.  EGR Thermal Valve
  9.  Thermal Vac Valve
Improper Adjustment
Improper Float Level
Stuck Open or Ruptured Diaphragm
Improper Mixture
Improper Adjustment
Ruptured Diaphragm or Loose Vacuum Hose
Electrode-Deterioration
Cable Deterioration
Terminal Corrosion or
Terminal Erosion
Ruptured Diaphragm or Loose Vacuum Hose
Deteriorated
Improper Adjustment
Ruptured Diaphragm or Loose Vacuum Hose
Improper Lash
Burned or Eroded
Stuck
Melted (Overheated)
Hose or Pump
Clogged
Stuck
Stuck
Clogqed
Stuck
Stuck
Normal Opening - Delayed Opening
1/8" Low - 1/8" High
Operational - Failed
1/2 Turn In - 1/2 Turn Out
1/8" Low - 1/8" High
Operational - Failed
Wide Gap - Fouled
Open - Grounded
New - Old
New - Old
Operational - Failed
New - Old
SPEC  -10° - SPEC  +10°
Operational - Failed (Open)
Specification - 1/16" Excess
New - Old
Operational
Operational
Operational
Operational
Operational
Operational
Operational
Operational
Operational
Failed
Failed
Failed
Failed
Failed
Failed
Failed
Failed
Failed
(Open)
(Closed)
(Open)
(Closed)

(Closed)
(Open)

-------
6.1.1.2   Float and Valve

          Float adjustment is critical  to correct carburetor
metering.  Float adjustment is most likely to be high,
although low float level  is also possible.  Three float
settings are recommended  for  testing:   specification,  1/8-
inch low, and 1/8-inch high.   The range of float adjustments
is reasonable because significant driveability (lean)  or
emissions (rich) impacts  would occur.

6.1.1.3   Power Valves

          Power valves may be either vacuum or mechanically
operated.  A representative carburetor  using both designs
should be tested.   The vacuum- operated power valve would be
tested in operational and failed (ruptured vacuum diaphragm)
configurations.  The mechanically-operated power valve would
be tested when set to specification and when held open by
incorrectly adjusted linkage.

6.1.1.4   Idle Adjustment

          Setting  the idle adjustment  on catalyst-equipped
vehicles can be difficult, particularly if a tap is not
provided upstream  of the  catalyst.   The idle adjustment is  a
basic step in current tune-up practice.  It is, therefore,
likely that some misadjustment of the  mixture will  occur for
mechanics who attempt to  set  idle in the same manner as for
noncatalyst vehicles.  The idle adjustment range is restricted,
however, by limiter caps  on the rich side and lean misfire
on the lean side.   The idle adjustment  parameter would,
therefore, be made by setting the idle  one turn rich and one
turn lean of the as-received  adjustment.
                          6-4

-------
6.1.1.5   Metering Rods

          The metering rods are operated  by the throttle
linkage and are adjusted to select the correct metering jet
size for the load condition.   The metering rods would  be
tested at the following settings:  specification,  1/8-
inch low, 1/8-inch high.  This range of adjustments  is
reasonable and creates significant driveability (lean) or
emissions (rich) degradation.

6.1.1.6   Vacuum Break Valve

          The vacuum break valve provides vacuum modulated
choke opening to reduce the mixture enrichment under high
vacuum conditions.  The characteristic failure of  the  vacuum
break valve is a ruptured diaphragm which prevents  load
modulated choke opening and may also introduce a vacuum
leak.  The vacuum break valve  would be tested  in a  normally
operating mode and a failed mode simulated by  a disconnected
vacuum line.

6.1.2     Ignition System Components

          The following ignition system components  are
recommended for testing on both air injection  and  nonair
injection-equipped vehicles:

          t    Spark plugs
          •    Ignition wires
          •    Distributor cap
          •    Distributor rotor
          t    Vacuum advance  unit
          t    Electronic ignition trigger circuit
          •    Basic timing adjustment
                          6-5

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6.1.2.1   Spark Plugs

          Spark plugs are a routine tune-up component and
have been included in numerous previous studies.   However,
plug failure and its relationship to increased emissions on
catalyst-equipped vehicles has not been tested under controlled
conditions using the FTP.
          The characteristic defect of spark plugs is the
electrode gap.   This normally increases as  plugs  age due to
electrical erosion.   The increased gap increases  the required
firing voltage  and reduces the spark firing time.   Oil
burning or rich mixtures can result in plug fouling which
closes the gap  and results in a shorted plug in which the
spark does not  fire.  Spark plugs should be tested in three
configurations:  specified plug gap, all plugs set to twice
the specified plug gap to simulate aged plug,  and  one plug
shorted to simulate  fouling in one cylinder.

6.1.2.2   Igni tion Wi res

          Igni-tion wires are subject to two failure modes:
breakage at terminals and grounding through the insulation.
An open wire creates a high resistance for  the spark voltage
to cross.  The  plug  usually fires but the firing  time and
energy discharged through the plug is low which causes
misfire at high load and speed.  The high potential which
must be reached to fire the plug may cause  arcing  to ground
or cross firing in the distributor cap.  Similar  failure
occurs with a grounded ignition wire in which  a wire has
touched the exhaust  manifold and melted the insulation.
This defect is  characterized by low firing  voltage and
causes misfire  at idle.  Therefore, the following  wire
conditions should be tested:  normal (new)  wire,  one grounded
wire, and one broken wire with high internal resistance.
                          6-6

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6.1.2.3   Distributor Cap

          The distributor cap is subject to several  failure
modes:  terminal  corrosion, carbon tracking leading  to low
resistance paths  to ground or to other terminals, and wear
or breaking of the primary high voltage terminal.  These
defects occur in  old distributor caps.  Therefore, this
defective component's effect on emissions should be  tested
by comparing emissions from a defective distributor  cap
removed from a vehicle to emissions from a new cap.

6.1.2.4   Distributor Rotor

          The rotor has the same failure modes as the cap.
Carbon tracking can occur across the rotor to the grounded
distributor shaft.  Corrosion and electrical  erosion of the
rotor terminals can also occur.  This defective component
should be evaluated by testing an old rotor compared to a
new one.

6.1.2.5   Vacuum Advance

          The vacuum advance is critically related to emis-
sions because permanent loss of vacuum advance (i.e., retarded
timing) requires  additional fuel flow to compensate  for the
more  inefficient combustion.  Vacuum advance is disabled by
failures of the vacuum advance diaphragm.  This failure mode
can be simulated by disconnecting the vacuum line to the
advance unit.  A baseline test would be performed with the
advance unit operational to evaluate the change in emissions.
Some  failures of the vacuum control valves or circuits of
the TCS, SCS, and ESC systems can also cause loss of spark
advance.
                          6-7

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6.1.2.6   Electronic Ignition Magnetic Triggers

          Breakerless electronic ignition systems are widely
used in post-1975 model-year vehicles.  The timing signal  to
fire each cylinder is detected electromagnetically .   Failure
of the magnetic timing bar is not  likely.  However,  the
electronic circuits which sense the trigger pulse and cause
the coil  to discharge, may become  defective due to corrosion,
temperature cycling, or vibration.   Detection  of  the trigger
signal then becomes intermittent which results in random
misfire on all  cylinders.  This component defect  should be
evaluated by testing a new and an  old triggering  circuit.
The old triggering circuit would be determined to have been
defective, or an intermittent misfire could be programmed
into the  vehicle.

6.1.2.7   Basic Ignition Timing

          Most studies of basic timing mi sad justment has
been performed on pre-catalyst vehicles;  or using hot start
tests.  The range of 10° timing advance and retard from
specification should be tested to  evaluate the effect of
i ncorrect timing.
          The other emissions-related ignition system
components ranked relatively low in criticality for  post-
1975 model-year vehicles.  These components include  points,
coil, resistor, distributor drive  and mechanical  advance.
The misfire conditions these components create should be
adequately represented by the use  of the  secondary ignition
component defects which cause intermittent misfire (wide
plug gap, high resistance wires, defective cap or rotor,
defective advance mechanism and defective El trigger).
                          6-8

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6.1.3     Air Induction System

          The only air induction component recommended for
testing is the thermostatic air cleaner (TAG)  vacuum hoses
or vacuum motor.   This failure introduces  a vacuum leak and
prevents heated air from entering the carburetor during cold
start.   The TAG failure would be evaluated by  testing with
and without the TAG vacuum hose disconnected.   Other TAG
components are not recommended for testing since they were
not as  emission-critical  as the vacuum components.
          The air cleaner is not recommended for testing
since it is only  moderately emission-critical  due to low
probability of failure and high probability of repair.  In
addition, considerable data is available which indicated
that air cleaner  restriction is not strongly related to FTP
emission levels on catalyst vehicles.

6.1.4     Fuel Injection System

          No fuel injection components are recommended for
testing since they ranked low in emissions criticality.
Fuel injection is used on only a small percentage of the
current U.S. vehicle population.

6.1.5     Mechanical Components

          Two exhaust valve characteristics are recommended
for testing:  valve adjustment, and burned valves.  Valve
adjustment is an  important scheduled maintenance item for
vehicles with mechanical  valve lifters (typically, 4-cylinder
engines).  On these vehicles^ the valve lash or clearance  of
the valve linkage must be adjusted to allow proper spacing
for thermal and mechanical expansion and elongation of the
various components.  Excessive lash results in noisy valve
operation and insufficient valve opening.   Insufficient lash
                          6-9

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holds the valves open too long, permitting unburned gases to
escape from the cylinder.  Valve lash is set by adjusting
screw stops on the rocker arm.  Evaluation of improper valve
adjustment would be made by comparing emissions of a vehicle
with all  cylinders set to correct lash compared to all
cylinders set to 1/16-inch shorter lash.
          Burned exhaust valves can result from normal
operation of the engine over extended mileage accumulation
and is a  relatively common defect in high mileage vehicles.
Burned valves would be evaluated by testing a vehicle with
nominal  valve condition determined by a compression check.
This would be compared to the vehicle tested with one valve
burned or ground to cause half of the nominal compression.
Other mechanical components (rings, head gaskets, cams and
cam shafts) are not recommended for testing due to low
criticality and probability of failure within the certifica-
tion period.

6.1.6     Emission Control Components

          Nine emission control components are recommended
for testing due to their expected impact on emissions.  Only
two components can cause detectable performance degradation:
heat riser and PCV valve.  The other components, however,
were included since relatively little data is available
regarding their impact on emissions from catalyst-equipped
vehicles.  The components recommended for testing are the
fol1owi ng :

          •    PCV valve
          t    Air injection system
          •    EGR valve
          t    EGR thermal vacuum valve
          •    EGR back pressure sensor
          •    Thermal vacuum valve
                          6-10

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          •    Spark delay valve
          •    Catalyst
          •    Heat riser

6.1.6.1   PCV Valve

          The PCV valve fails when it is  clogged  by oil  or
participates.  Failure of the PCV valve would  be  evaluated
by testing the nominally functioning PCV  system and the  PCV
hose plugged.

6.1.6.2   Air Injection System

          On vehicles equipped with  air injection,  the
effect of a failure of the air injection  system would  be
evaluated by disconnecting the air delivery  hose  and compar-
ing the emissions to the normal  system.

6.1.6.3   EGR Valve

          The EGR valve fails if the vacuum  hose,  vacuum
amplifier, or valve diaphragm are defective.   In  addition  to
loss of EGR, a vacuum leak is introduced.   Ported  EGR  vacuum
is proportional  to throttle opening  and vacuum leaks do  not
have significant affect on air fuel  ratio;  therefore,  vacuum
system failure only defeats EGR.  However,  manifold vacuum-
activated EGR valves are closed  by vacuum  at  idle  and  opened
by spring action as vacuum decreases during  acceleration.
These valves can create idle lean misfire  in  addition  to
defeating EGR.  The test of the  EGR  valve  would be  based on
the manifold vacuum operated valve and would  involve discon-
necting the vacuum line at the EGR valve.   Two tests would
be performed, one with normally  functioning  EGR,  and one
with EGR disconnected.
                           6-11

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6.1.6.4   EGR Thermal  Vacuum Valve (EGR-TVV)

          Several  vehicles use a thermal  vacuum valve to
disable EGR during the cold start to improve driveabi1ity.
Failure of this valve  to open defeats EGR at all  operating
temperatures.  The ported vacuum EGR valve failure is also
similar to this defect since ported vacuum leaks  do not
cause lean misfire.   The defects of both  a stuck  EGR-TVV and
defective ported vacuum EGR valve will  be evaluated by
testing a vehicle  with normal EGR-TVV and with the EGR  line
disconnected and plugged.

6.1.6.5   EGR Backpressure Sensor

          The backpressure sensor modulates EGR in proportion
to load.  The sensor can be clogged or  disabled by the  hot
and corrosive exhaust  gases.  This defect would be evaluated
by testing a vehicle with normally functioning EGR and  with
the backpressure sensor's exhaust probe plugged.

6.1.6.6   Thermal  Vacuum Valve

          The thermal  vacuum valve selects full vacuum
advance rather than  throttle, speed, or transmission modulated
advance during cold  or hot engine temperatures to promote
higher engine speed.  Failure of the valve to switch to
modulated vacuum advance results in more  spark advance  on
average during the FTP.  This defect would be simulated  by
routing the vacuum lines so that manifold vacuum  is always
connected to the distributor.  The defect and nominal vacuum
routing would be tested to evaluate the effect of the defect.

6.1.6.7   Spark Delay  Valve

          The spark  delay valve fails when the check valve
remains open due to  dirt or diaphragm rupture.  This results
                          6-12

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in normal  vacuum advance.   The alternative failure, restricted
or clogged valve orifice is analogous  to disabled vacuum
advance and is not considered further  in this component
category.   The defect would be evaluated by testing vehicles
with a nominal spark delay valve and with the valve removed
from the vacuum advance hose.

6.1.6.8   Catalyst

          Catalyst defects sufficient  to cause emissions
failure are unlikely unless some other ignition or carburetor
defect has occurred which  subjected the catalyst to excessive
temperature.  Even after the primary defect has been corrected,
the defective catalyst remains and contributes to higher
emissions  than normal.  To evaluate this defect, misfire
would be established and continued during loaded operation
until continuous catalyst  temperature  and raw exhaust emis-
sions of HC have increased to indicate probable catalyst
failure.  The test sequence would then be performed without
the misfire and compared to baseline emissions prior to the
mi sfi re.

6.1.6.9   Heat Riser

          The heat riser is most likely to fail in the hot
exhaust position which prevents rapid  intake manifold warm-
up.  This  defect is not well documented in the literature
for catalyst-equipped vehicles and is  expected to degrade
cold start performance.  This defect would be evaluated by
testing vehicles with normally functioning heat riser and
the heat riser jammed in the open position.
                         6-13

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6.2       TEST PROTOCOL

          The original  equipment components selected for
testing would all  be subjected to the following general  test
protocol :

          •    Select representative test vehicles.
          0    Set all  components to nominal  specifications.
          •    Precondition test vehicle.
          •    Perform baseline tests.
          t    Establish defect condition.
          •    Precondition test vehicle.
          •    Perform defect condition tests.
          t    Perform restorative maintenance.
          t    Precondition test vehicle.
          •    Perform baseline test.
          t    Retest or perform additional  restorative
               maintenance if second baseline emissions
               differ by more than 25 percent for HC,  CO,  -
               and NO  from first baseline  test.

Various aspects of the test protocol are discussed in  the
following  paragraphs.

6.2.1     Vehicle  Selection

          Test vehicles would be selected to  represent
typical weight classes and engine sizes equipped  with  the
specific  component to be evaluated.   Where  applicable, one
vehicle with each  of the following catalyst emission control
systems should be  tested for each component:
          •    Pelleted catalyst with air
          t    Pelleted catalyst without air
          t    Monolith catalyst with air
          t    Monolith catalyst without air
                           6-14

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          Testing is not recommended on pre-1975 model-year
or noncatalyst-equipped vehicles since they represent small
and decreasing fractions of the vehicle population.

6.2.2     Preconditioning

          Preconditioning should be performed by accumulating
300 miles of freeway driving followed by approximately
10 minutes of surface street driving, or the first 505
seconds of the LA-4 driving schedule.  Each vehicle  would be
preconditioned prior to baseline and defect testing.  Precon-
ditioning and cold soak would be performed in accordance
with 40 CFR 85.076-12b for vehicles receiving the FTP.

6.2.3     Test Fuel
          All  preconditioning and testing would be performed
with tank fuel.

6.2.4     Inspection and Maintenance

          Each  vehicle would be fully inspected prior to
each test series to ensure that the basic engine adjustments
are correct, that the ignition and carburetor systems are
functioning normally, and that all vacuum, vapor, and air
hoses are correctly routed and connected.  During each test
series, only the specific component under study would be
adjusted or disabled.

6.2.5     Emission Tests

          Ideally, the full  FTP should be used to clearly
define emission  changes resulting from component defects
since the criteria for emission-criticality includes failure
of one or more  of the FTP emission standards.  However, FTP
                         6-15

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testing is expensive and, for those component defects which
cause large emission increases, a short inspection test is
probably adequate and cost-effective to confirm that emissions
have increased significantly.  Therefore, a short test
sequence is recommended for most components, with FTP testing
recommended only for those components which have significant
effects on cold start operation.

6.2.5.1   Short Tests

          Considerable data on the relationship between
various short tests and the FTP have been, and are currently
being, developed by the EPA.   Although numerical relationships
between short tests and the FTP are not precise, significant
emission increases on short tests indicate a probable FTP
failure.  However, a vehicle  which passes a short test may
still fail the FTP.
          In order to minimize the possible errors of emission
by the short test, the following two short tests are
recommended:

          t    Clayton Key Mode Test
          t    Federal 9-Mode CVS Test

          The Key Mode test is recommended because it provides
modal emission results.  The  Federal 9-Mode is recommended
since it simulates the FTP.  A separate idle test is not
recommended, however, since the Clayton Key Mode test includes
an idle mode.  Each of the selected components would be
tested using these cycles.  An emission increase of 100 per-
cent in any mode or in the Federal 9-Mode composite would
constitute a significant increase.  As an alternative criteria,
the EPA Project Officer could establish failure limits for
each test.
                          6-16

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          The components listed below are recommended for
testing using the short tests only.   These components are
expected to have significant increases in hot running emis-
sions which would be detected by the short tests.   If increases
are not observed, it is likely that  FTP emissions  would not
be significantly altered by the defective component.   These
components include the following:

          t    Carburetion System
               Float and valve
               Power valve
               Metering rod
               Idle adjustment

          •    Ignition System
               Spark plugs
               Wires
               Cap
               Rotor
               Vacuum advance
               Electronic ignition triggers
               Basic timing

          •    Engine Mechanical  System
               Valve lash
               Exhaust valves

          •    Emission Control System
               Catalyst
               Air injection system
               PCV valve
               Spark delay valve
               EGR valve
               EGR back pressure sensor
               EGR thermal vacuum  valve
               Distributor thermal vacuum valve
                            6-17

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6.2.5.2   FTP Tests

          Several  components have a significant effect on
cold start or cold running emissions.   Defects in these
components may cause an FTP emissions  failure, but not
necessarily affect short test emissions which are measured
when the vehicle and catalyst are warmed up.   The following
components would receive the FTP in addition  to the short
test:

          •    Carburetion System
               Choke
               Vacuum break valve

          •    Air Induction System
               Thermal  (heated)  air inlet

          t    Emission Control  System
               Heat riser

6.2.5.3   Test Procedures

          The FTP  should be performed  in accordance with
40 CFR 85.076-12b.  The Federal  9-Mode test should be per-
formed in accordance with 40 CFR 85.076-12b except that
preconditioning and cold soak would be deleted.  The Key
Mode test should be performed using NDIR analyzers for HC,
CO, and NO  emissions and the appropriate speed and power
          /\
absorption for the vehicle weight.
          During the road driving and  dynamometer driving, a
general driveability data sheet  should'be filled out by the
test driver giving a general description of the vehicle's
performance under  baseline and defect  conditions.  This
provides data on the symptoms and detectabi1ity of the
defects to the vehicle operator.
                            6-18

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55.   Franklin, T.M., et  al, "Simulated  Road Test  Evaluation
     of the Effect of Gasoline Additives on Exhaust Gas
     Emissions,"  SAE 720942, October 31  - November 2, 1972.

56.   Fetzloff, J.B., et  al , "Fuel Detergency - Effects on
     Emissions,"  SAE 720941, October 31  - November 2, 1972.

57.   "New Emission Control  System Meets  1976 Requirements,"
     SAE J. Automotive Engineering, v 81, nl, January, 1973.
                          R-4

-------
58.   LaMasters,  G.D.,  "Fuel  Injection - Another Tool  for
     Emission Control,"  SAE  720679,  November 4, 1971.

59.   Callahan, J.M.,  "GM's "Hottest" Automotive Emission
     Eliminator," Automotive Industries v 174,  n4,  August 15,
     1972.

60.   Gunderson,  J.A.,  "FTP/Short Cycle Correlation  Testing
     for 207(b)  Implementation Catalyst Equipped Vehicles,"
     Volume 1, PB-242  588/2ST, April, 1975.

61.   Schweitzer, P.M.,  "Control  of Exhaust Pollution  through
     a Mixture Optimizer," SAE 720254, January  10-14,  1972.

62.   Powell, J.  David,  "Closed Loop  Control  of  Internal
     Combustion  Engine  Exhaust Emissions," PB-239 850/1ST,
     February, 1974.

63.   Storment, John 0.,  "A Surveillance Study of Smoke from
     Heavy-Duty  Diesel-Powered Vehicles - Southwestern
     U.S.A.," PB-232  682/5,  January, 1974.

64.   Melton, C.W., "Chemical and Physical Characterization
     of Automotive Exhaust Particulate Matter in the  Atmosphere
     (Year Ending June  30, 1972)," PB-227 413/2, June, 1973.

65.   Seizinger,  D.E.,  "Oxygenates in Automotive Exhaust.
     Effect of an Oxidation  Catalyst," PB-227 097/3,  December,
     1973.

66.   Moran, John B.,  "Effect of Fuel Additives  on the  Chemical
     and Physical Characteristics of Particulate Emissions
     in Automotive Exhaust," PB-222  799/9, December,  1972.

67.   Storment, John 0.,  "Evaluation  of Diesel Smoke Inspection
     Procedures  and Smokemeters," PB-212 796/7, July,  1972.

68.   "Interim Standards  Report by the Committee on  Motor
     Vehicle Emissions  of the National Academy  of Sciences
     to Environmental  Protection Agency," PB-245 806/5ST,
     April, 1972.

69.   John, James E.,  "Consultant Report on Emissions  Control
     of Engine Systems  to NAS Committee on Motor Vehicle
     Emissions," PB-242  097/4ST, September,  1974.
                                               *
70.   "Feasibility of  Meeting the 1975-1976 Exhaust  Emissions
     Standards in Actual  Use," Committee on  Motor Vehicle
     Emissions,  NAS,  June, 1973.

71.   Matula, Richard  A.,  "Consultant Report  on  Emissions and
     Fuel-Economy Test  Methods and Procedures to NAS  Committee
     on Motor Vehicle  Emissions," PB-242 093/3ST, September,
     1974.
                          R-5

-------
72.   Hightower, "Consultant Report on an Evaluation of
     Catalytic Converters for Control of Automobile Pollutants
     to NAS Committee on Motor Vehicle Emissions," -PB-242
     092/5ST,  September, 1974.

73.   Brattain, "Consultant Report on Field Performance of
     Emissions-Controlled Automobiles to NAS Committee on
     Motor Vehicle Emissions," PB-242 091/7ST, November,
     1974.

74.   Meltzer,  "A Review of Control Strategies for In-Use
     Vehicles," PB-241 768/1ST,  December, 1974.

75.   Roessler, "Status of Industry Progress Towards Achieve-
     ment of the 1975 Federal Emissions Standards for Light-
     Duty Vehicles," PB-239 691/9ST, July, 1972.

76.   Beagguist, K.,  "Experiments with a Catalytic Cleaner
     for Car Engine  Exhaust Gases," N75-12455/2ST.

77.   "Emissions Control Technology of Heavy-Duty  Vehicle
     Engines," PB-236 899/1ST, December, 1973.

78.   Gockel , J.L., "An Evaluation of the Effectiveness of
     Automobile Engine Adjustments to Reduce Exhaust Emissions
     and An Evaluation of the Training Required  to Develop
     Personnel Competent to Make the Adjustments," PB-237
     040/1ST,  June 22, 1973.

79.   Bodan, "Technical Evaluation of Emission Control
     Approaches and  Economics of Emission Reduction Require-
     ments for Vehicles Between  6,000 and 14,000  Pounds
     GVW," PB-232 773/2, November, 1973.

80.   Fleming,  "Durability of Advanced Emission Controls for
     Heavy-Duty Diesel and Gasoline Fueled Engines," PB-232
     441/6, September, 1973.

81.   "NAS Report on  Technological Feasibility of  1975 - 76
     Motor Vehicle Emission Standards.  Automotive Spark
     Ignition  Engine Emission Control System to  Meet the
     Requirements of the 1970 Clean Air Amendments," PB-224
     862/3, May, 1973.

82.   "NAS Report on  Technological Feasibility of  1975 - 76
     Motor Vehicle Emission Standards.  Evaluation of Catalyst
     as Automotive Exhaust Treatment Devices," National
     Academy of Sciences, PB-224 860/7, March, 1973.

83.   Gomph, Henry L., "Evaluation of GM 1976 Prototype
     Vehicles, A Catalytic Exhaust Manifold Systems," PB-218
     686/4, June, 1972.
                          R-6

-------
84.   "Control  Strategies for In-Use Vehicles," PB-218 942/1,
     November, 1972.

85.   Austin, Thomas C., "An Evaluation of a 1975 Prototype
     Chrysler  Passenger Car," PB-220 032/7, October, 1972.

86.   "Control  of NOX  Emissions From Mobile Sources," PB-211
     376.

87.   Trayser,  "A Study of the Influence of Fuel  Atomization
     Vaporization,  and Mixing Processes on Pollutant Emissions
     from Motor-Vehicle Powerplants," PB-209 476, January 31,
     1972.

88.   Thomson,  John  C., "An Evaluation of the Emissions
     Characteristics  of the Esso Well Mixed Thermal  Reactor,"
     PB-220 034/3 March, 1972.

89.   Thomson,  John  C., "A Report on the Exhaust Emissions
     from a Turbocharged Volkswagen," PB-218 423/2,  May,
     1971.

90.   "Control  Techniques for Carbon Monoxide,  Nitrogen
     Oxide, and Hydrocarbons Emissions from Mobile Source,"
     PB-190 264, March, 1970.

91.   "Study of Catalytic Control of Exhaust Emissions for
     Otto Cycle Engines," PB-193, 533, 1970.

92.   "Effect on Emissions by Detuning Vehicles Equipped with
     Catalytic Converters," Preliminary Report,  Project M-
     300, California  Air Resources Board, August", 1976.

93.   "Emission Reductions from Inspection and  Repair of
     Catalyst-Equipped Vehicles Obtained From  Rental Agencies,"
     Preliminary Report #VEC-76-34, Project M-300, California
     Air Resources  Board, August, 1976.

94.   "California Vehicle Inspection Program Riverside Trial
     Program Report," California Bureau of Automotive Repair,
     May, 1976.

95.   "Evaluation of Mandatory Vehicle Inspection and Mainte-
     nance Program,"  California Air Resources  Board, August 2,
     1976.

96.   Panzer, J., "Idle Emissions Testing: Some Effects of
     Engine Malfunctions on Emissions," presented at the
     Fourth Annual  North American Motor Vehicle Emissions
     Control Conference, November, 1975.

97.   "A Study of Fuel Economy Changes Resulting From Tampering
     With Emission  Controls," EPA-ECTD Report  #74-21 DWP,
     January,  1974.
                          R-7

-------
98.   "The Effect of Ignition  Timing  Modifications  on  Emissions
     and Fuel  Economy,"  EPA-ECTD Report  #76-4  AW,  October,
     1975.

99.   Poston, H.W. and J.  Seliber, "Chicago's  Experience  in
     Vehicle Emission Testing,"  SAE  Paper  No.  760368,  February
     23-17, 1976.

100. Maugh, R., "Comments on  the Changing  Relationship
     Between Automotive  Maintenance  and  Air  Quality,"  presented
     at the Fourth Annual North  American Motor Vehicle
     Emission Control Conference, November 5-7, 1975.

101. Oberdorfer, P.E., "Reducing Fuel  Consumption  and  Emissions
     by an Optimizing Tune-up"  presented at  the Fourth Annual
     North American Motor Vehicle Emission Control  Conference,
     Anaheim, California, November 5-7,  1975.

102. Pattison, J.N. and  G.A.  Issacs, "A  Diagnostic  Procedure
     Using Emission Data  to Reduce Emissions," paper  No.
     75-42.5, presented  at the  68th  Annual Meeting  of  the
     Air Pollution Control Association,  June  15-20, 1975.

103. "Automotive Industries,  Engineering Specifications  and
     Statistical Issues  for 1974 and 1975,"  Chilton Co.,
     April 1975 and April 1976.
                          R-8

-------
        Appendix A




CRITICALITY INDEX RANKINGS

-------
AUTOMOTIVE PARTS  STUDY  - EPA CONTRACT NO. 68-O1-1957
CRITICALITV INDEX RANKING - EARLY
MODELS




PKINCIPAL RANKING - MC
PART
CODE
2.
3> 2.
1 5.
w 5.
5.
1.
1.
2.
2.
2.
2.
2.
5.
5.
5.
2.
6.
6.
6.
6.
6.
1.
1.
1.
1.
5.
6.
1.
1.
1.
3.
3.
3.
3.
1.
7.
9.
1.
1.
2.
3.
2.
3.
3.
1.
10.
3.
3.
3.
3.
0
0
"i
4
_5
*
6
2
I
0
0
6
2
3
0
5
I
2
7
1
I
10
9
3
5
PART
NAME
SPARK PLUGS
IGNITION WIRES
VALVE LlFTER/SPR
VALVE StALS
EXHAUST VALVES
LhOKE MtCnANlSM
POwEK VALVES
ROTOR
CAP
POINTS
CUIL
bALLAST RESISTOR
VALVE CAM LOBES
VALVE GUIDES
PISTON KINGS
DISTRIBUTOR DKIV
EVAP CANISTER
AI MUSES
AI PUMP/bELTS
PCV VALVE
HEAT (USER
IDLE ADJUSTMENT
FLOAT AND VALVE
VAC BRK VALVE
ACCELERATOR PUMP
RANK
1
2
J
H
5
6
7
e
9
10
11
12
13
1*
15
16
17
IB
19
20
21
22
23
2*
25
MC 	
Cl
0.26!>E + 02
0.8386+Oi
0.845E+00
0.501E+00
0.507E+00
0.411E+00
0.411E+00
0.231E+00
0.22HE+00
0.1 126+00
0.69AE-01
0.6V.E-01
0.507E-01
0.507E-01
0.i07E-01
0.385E-01
0.356E-01
0.275E-01
0.27!>fc-01
0.266E-01
0.259E-01
0.208E-01
0.207E-01
0.205E-01
0.2056-01
	 CO 	
RANK C I
5*
55
3
4
5
1
2
50
<*9
f7
56
58
12
13
1*
51
85
16
17
8
126
10
6
18
19
0.0
0.0
O.B<»5E«00
0.507E*00
0.507E+00
0.205E+01
0.205E»01
0.0
0.0
0.0
0.0
0.0
0.507E-01
0.507E-01
0.507E-O1
0.0
0.0
0.275E-01
0.275E-01
0.266E+00
0.0
0.208E»00
0.<.l
-------
AUTOMOTIVE  PARTS STUDY - EPA CONTRACT  NO. 68-01-1957
    CRITICAL!TY  INDEX RANKING - EARLY  MODELS
PRINCIPAL RANKING - MC
PART
CODE
f 6.
r- 2.
3.
3.
6.
b.
1.
a.
i.
5.
6.
b.
2.
1.
6.
5.
1.
. 3.
3.
2.
6.
6.
2.
6.
t>.
2.
3.
1.
1.
1.
2.
4.
2.
3.
4.
1.
2.
4.
3.
2.
5.
3.
1.
1.
2.
3.
2.
11.
5.
4.
3
7
3
4
2
2
0
0
1
1
3
6
0
2
4
0
7
1
2
0
1
5
0
4
a
PART
NAME
EVAP FRSH AIR
SPARK DbLAY VLV
TAC VAC MOTOR
TAC VAC HOSES
PCV HOSES
EVAP MOSES
FUEL FILTER
AIR CLEANER ELEM
METERING JETS
HEAD GASKETS
PCV FRSHAIK FLTR
FUEL TANK/CAP
MAG/OPT TRIGGERS
METERING RUDS
EVAP VPKLIG SEP
CAMSHAFTS
GASKETS
TAC ShRUUD
TAC THERMOSTAT
CONDENSER
Al MANIFOLD
EVAP VAPOR CONTR
IGN TIMING ADJ
TCS CEC VALVt
EGR VAC AMP
RANK CI
26
27
26
29
30
31
32
33
34
35
36
37
38
39
40
Hi
42
43
44
45
46
47
48
49
50
0.183E-01
0.172E-01
0.169E-01
0.169E-01
0.154E-01
0.154E-01
0.147E-01
0.144E-01
0.126E-01
0.121E-01
0.120E-01
0.115t-01
0.114E-01
O.I13b-01
0.113E-01
0.694E-02
0.685E-02
0.673E-02
0.673E-02
0.657E-02
0.607E-02
0.545E-02
0.540E-02
0.425E-02
0.359E-02
ICONT'U)
RANK
87
52
63
64
83
86
46
7
20
21
11
90
53
9
88
24
43
61
62
48
25
89
60
26
99
CO 	
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.2886*00
0.126E-01
0.121E-01
0.120E*00
0.0
0.0
0.227E»00
0.0
0.694E-02
0.0
0.0
0.0
0.0
0.607E-O2
0.0
0.0
0.425E-02
0.0
RANK
102
3
67
68
97
101
49
70
38
94
98
105
58
39
103
95
44
65
66
51
106
104
7
114
4
• NOX — —
CI
0.0
0.172E+00
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0. 5405-0 L_
0.0
0.718E-01
HANK
72
35
46
47
67.
71
26
4
15
8
- 68 .
75
36
16
73
9
21
44
45
23
76
74
43
98
90
SMOKE 	
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.481F-01
0.0
0.804E-02
0.0
0.0
0.0
0.0
0.0
0.462E-02
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
    CKITICALITY INDEX RANKING  - EARLY MODELS
PRINCIPAL
PART
CODE
1.
3=> 1.
» I:
5.
1.
3.
6.
1.
1.
6.
5.
5.
5.
1.
6.
6.
1.
1.
1.
5.
2.
6.
5.
6.
3.
3.
1.
1.
1.
3.
2.
1.
3.
3.
1.
1.
1.
2.
2.
3.
3.
3.
3.
3.
*.
3.
10.
5.
3.
*
6
1
4
5
9
0
1
2
10
3
2~
3
0
1
2
7
3
5
1
1
4
4
0"
1
PART
NAME
CHOKE MtCHANlSH
POWER VALVES
VALVE LlFTtR/iPR
VALVE StALS
EXHAUST VALVES
FLOAT AND VALVE
AIR CLEANEK ELEM
PCV VALVE
METERINU HODS
IDLE ADJUSTMENT
PCV FRSHAIR FLTR
VALVE CAM LOBES
VALVE GUIDES
PISTON RINGS
IDLE STHSOLEN01D
AI HOSES
AI PUMP/BELTS
VAC BKK VALVE
ACCELERATOR PUMP
METtRlNli JETS
HtAU GASKETS
VACUUM ADVANCE
DECbL VALVE
CAMSHAFTS
AI MANIFOLD
RANK
6
7
3
4
5
23
33
20
39
22
36
13
14
15
53
18
19
24
25
34
35
av
67
41
46
RANKING - CO
• HC 	
CI
0.411E+00
0.4116*00
0.8456*00
0.5076*00
0.507E+00
0.207E-01
0.144E-01
0.26&E-01
0.113E-01
0.208E-01
0.120E-01
0.507E-01
0.507c-01
0.507t-01
0.309E-02
0.275E-01
0.275E-01
0.205E-01
0.205E-01
0.126E-01
0.121E-01
0.0
0.854E-03
0.690E-02
0.607E-02
RANK
1
2
3

-------
AUTOMOTIVE PARTS  STUDY - EPA CONTRACT NO. 68-01>1957
CRITICALITY INDEX RANKING - EARLY MODELS
PRINCIPAL RANKING - CO
PART
CODE
6.
2.
3» 6.
1 6.
<* 1.
1.
6.
6.
6.
0.
2.
b.
6.
6.
6.
1.
•
•
•
*
•
2.
2.
2.
2.
5.
3.
3.
3.
2.
2.
3.
10.
10.
5.
3.
10.
7.
b.
6.
1.
1.
3.
3.
3.
4.
1.
2.
3.
3.
4
3
4
3
2
3
5
3
2
2
6
6
2
2
~2"
I
2
7"
B
11
0 "
0
0
1
2
PART
NAME
TCS CEC VALVE
MECM ADVANCE
AI CHECK VALVES
AI AIR FILTER
THROTTLE DASHPOT
THRTTL i>osiTiONR
AI BYPAbS/DVRTR
STAI.EU PULLDOWN
ELEC ASSIST ChKfc
TCS VAC MUSES
DUAL D1APHM DIST
DIST START SULEN
OSAC VAC HOSES
ESC HOSES
SCS VACUM LINE
NEW CARb
RtflUlLT CARB
GASKETS
REbUlLUlNU KITS
IDLE ENRICHMENT
f-OEL F1LTEK
POINTS
CONDENSER
CAP
KOTOR
	 MC 	
RANK CI
49
88
51
54
75
79
60
62
63
64
90
68
70
80
82
84
65
42
86
87
32
10
45
9
8
0.4256-02
0.0
0.333E-02
0.278E-02
0.2776-03
0.206E-03
0.1966-02
0.171E-02
0.171E-02
0.154E-02
0.0
0.7786-03
0.4?6E-03
0.200E-03
0.120E-03
0.0
0.0
0.685E-02
0.0
0.0
0.1476-01
0.112E+00
0.657E-02
0.2288+00
0.2316+00

RANK
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
- CO 	
CI
0.425E-02
0.38SE-02
0.333E-02
0.278E-02
0.277E-02
0.206E-02
0.1966-02
0.171E-02
0.171E-02
0.1546-02
0.143E-02
0.7786-03
0.4266-03
0.200E-03
0. 120E-03
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
RANK
114
54
109
108
36
37
110
127
126
113
57
129
118
120
116
33
... 34
44
45
48
49
50
51
52
53
NOX 	
CI
0.0
0.0
0.0
0.0
0.0 . _
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
RANK
98
31
79
78
. 13..
14
80
124 .
123
96
34
127
109
114
104
10
11
21
22
25
26
27
28
29
30
SMOKE 	
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

-------
AUTOMOTIVE PARTS STUOY  -  EPA  CONTRACT NO. 68-01-1957
    CRITlCALlTY 1NDEX  RANKING - EARLY MODE.LS.
PRINCIPAL RANKING - NOX
PART
CODE
6.
7- *•
i 2.
•^ 6.
6.
6.
2.
6.
• 6.
6.
6.
b.
6.
b.
6.
6.
6.
6.
6.
6.
6*
b.
b.
b.
b.
4.
4.
3.
4.
5.
" 5.
11.
5.
H.
10.
<».
5.
4.
7.
•3.
4.
...*•
t.
7.
4.
8.
e.
8.
8.
10.
1
3
7
8
8
b
0
1
2
7
<»
3
5
1
5~~
7
10
11
4
b
1
3
*
5
5
PART
NAME
•
EGR VALVtS
EGR THERMO VALVE
SPARK DELAY VLV
EGR VAC AMP
TCS TEMP SWITCH
TCS TRANS SWITCH
1GN TIMING ADJ
TCS VAC SOLENOID
EGR HOSES/SEALS
THERMO VAC VALV
EGR SOLENOID VLV
TCS TIME DELAY
EGK TEMP SWITCH
Ob AC VAC OKIFICE
TCS THEKMU VALVE
EGR TIME DELAY
EGR CAHB SPACER
EGR BACKPRES SEN
OSAC VAC BYPASS
EliR SHEED/TKANS
ESC ELEC MODULE
ESC VAC VALVES
ESC TEMP SWITCH
ESC SPEED SWITCH
D1ST VACDECL VLV
RANK
113
114
27
50
52
55
48
56
57
59
115
bl
lib
58
bb
118
120
121
b5
117
71
72
73
74
7b
HC 	
CI
0.0
0.0
0.172E-01
0.35VE-02
0.327E-02
0.278E-02
0.540E-02
0.260E-0?
0.251E-02
0.217E-02
0.0
0.1B3E-02
0.0
0.230E-02
0.109E-02
0.0
0.0
0.0
0.130E-02
0.0
0.360E-03
0.3bOE-03
0.3bOE-03
0.3bOE-03
0.254E-03
RANK CI
92
94
52
99
109
107
bO
104
93
128
95
105
9b
114
lOb
98
101
102
116
97
118
11V
120
121
127
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
RANK
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
• NOX 	
CI
0.517E+00
0.204E»00
O.I72E+00
0.718E-01
0.654E-01
0.555E-01
0.540E-01
0.5?OE-01
0.502E-01
0.435E-01
0.4256-01
0.365E-01
0.234E-01
0.230E-01
0.219E-01
0.1B8E-01
0.144E-01
0.143E-01
0.130E-01
O.B78E-02
0.719E-02
0.719E-02
0.719E-02
0.719E-02
0.50BE-02
	 SMOKE 	
RANK CI
83
85
35
90
. 102 .....
100
43
95
84
128
86
97
87
108
99
89
92
93
111
88
113
115
116
117
126
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

-------
AUTOMOTIVE PARTS  STUOY  - EPA  CONTRACT NO. 68-O1-1957
    CRITICALITY INDEX  RANKING  - EARLY MODELS
PRINCIPAL RANKING - NOX
PART
CODE
6. 7.
t, 6. 6.
I 6. 6.
0° 6. 6.
6. 4.
6. 4.
B. 1.
1. 1.




'
. 1.
. 2.
. 2.
. 2.
. 3.
. 3.
. 3.
. 3.
. 3.
. 3.
. 3.
. 3.
. 3.
. 3.
I. 3.
1. 4.
2. 1.

5
1
5
9
0
1
2"
1
2
.3
1
2
3
4
5
6
7
8
9
10
11
0
0
PART
NAME
OSAC TEMP SENSOR
SCS VACUUM SOLEN
SCS SPEED SMllCh
SCS THbRMO VALVE
EGR "AC REDUCER
EGR CHECK VALVE
01STR VACUUM VLV
NEK CAKb
REbuiLT CARB
IDLE STPSOLENOID
THROTTLE DASMPOT
THRTTL POSITIONR
MbTErtlNG JETS
METERING RODS
VAC BKK VALVE
CHOKE MECHANISM
ACCELERATOR PUMP
POWER VALVbS
GASKE1S
REBUILDING KITS
FLOAT AND VALVE
IDLE ADJUSTMENT
IULE ENRICHMENT
FUEL FILTER
POINTS
RANK
69
77
78
81
119
122
83
84
B5
53
79
34
39
24
6
25
7
42
66
23
22
87
32
10
CI
0.432E-03
0.216E-03
0.216E-03
0.1B9E-03
0.0
0.0
0.430E-04
0.0
0.0
0.309E-02
0.277E-03
0.?06E-03
0.126E-01
0.113E-01
0.205E-01
0.4116+00
0.205E-01
" 0.411E+00
0.6R5E-02
0.0
0.207t-01
0.20BE-01
0.0
0.147E-01
0.112E»00
(CONT'D)
RANK CI
117
110
"112
113
100
103
133
15
30
31
20
9
18
1
19
2
44
6
10
45
46
47
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.309E-01
0.277E-02
0.206E-02
0.126E-01
0.2?7E»00
0.205E-01
0.205E+01
0.205E-O1
0.205E*01
0.0
0.0
0.414E+00
0.208E+00
0.0
0.0
0.0
	 NOX 	
RANK CI
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
0.432E-02
0.432E-02
0.432E-02
0.378E-02
O.lblE-02
0.316E-03
0.430E-04
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
	 SMOKE 	
RANK CI
112
103
106
107
91
94
133
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

-------
AUTOMOTIVE PARTS  STUOV  - EPA  CONTRACT NO. 68-01-1957
    CKITICALlTY  INDEX  RANKING - EARLY MODELS
PRINCIPAL RANKING - SMOKE
PART
CODE
5. 1.
t. 5. 1.
i 5. 1.
10 3. 2.
5. 1.
5. 1.
5. 2.
5. 4.
1




>. 5.
. 1.
• .!•
. 2.
. 2.
. 2.
. 3.
. 3.
. 3.
. 3.
. 3.
. 3.
.~3.
. 3.
. 3.
1. 3.
1. 3.

1
5
0
2
3
0
1
0
1
2
1
2
3
1
2
3
4
5
6
7
8
9
10
11
PART
NAME
VALVE L1FTEH/SPR
VALVE SEALS
EXHAUST VALVES
AIR CLEANER ELEM
VALVE CAM LOBES
VALVE GUIDES
PISTON RINGS
H6AU GASKETS
CAMSHAFTS
NEW CAKB
REBJILT CARB
IDLE STPSI3LENOID
THKUTTLE DASHPOT
THKTTL POSITIONR
METERING JETS
METERING RODS
VAC BRK VALVE
CHOKE MECHANISM
ACCELERATOR PUMP
POWER VALVES
GASKETS
REBUILDING KITS
FLOAT AND VALVE
IDLE ADJUSTMENT
IDLE ENRICHMENT
RANK
3
5
33
13
14
15
35
41
84
85
53
75
79
34
39
24
6
25
7
42
86
23
22
87
CI
0.507E+00
0.5076+00
0.144E-01
0.507E-01
0.507E-01
0.507E-01
0.121E-01
0.6946-02
0.0
0.0
0.309E-02
0.277E-03
0.20&E-03
0.126E-01
0.1136-01
0.205E-01
0.411E+00
0.205E-01
0.4116+00
0.6856-02
0.0
0.207E-01
0.2086-01
0.0
RANK
3
5
7
12
13
21
42
15
30
31
20
V
18
1
19
2
43
44
6
10
45
- CO 	
CI
0.845E + 00
0.507E+00
0.507E+00
0.2886+00
0.507E-01
0.507E-01
0.507E-01
0.121E-01
0.6946-02
0.0
0.0
0.309E-01
0.277E-02
0.206E-02
0.126E-01
0.227E+00
0.205E-01
0.205E+01
0.205E-01
0.205E+01
0.0
0.0
0.2086+00
0.0
RANK
87
90
91
70
88
89
92
94
95
33
34
35
36
37
38
39
40
41
42
43
44
. 45
46
47
48
NOX 	
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
RANK
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
25
SMOKE 	
CI
0.5636+00
0.3386+00
0.3386+00
0.481E-01
0.338E-01
0.338E-01
0.338E-01
0.804E-02
0.462E-02
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0-0
0.0
0.0

-------
AUTOMOTIVE PARTS  STUDY - EPA CONTRACT NO. 6B-01-1957
    CK1TICALITY  INDEX  RANKING - EARL* MODELS
PRINCIPAL RANKING - SMOKE (CONT'D)
PART
CODE
> I:
>- 2.
° 2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
3.
3.
3.
3.
3.
3.
3.
H
1
2
J
3
3
3
3
3
3
4
5
t>
7
H
V
10
11
1
1
1
1
1
3
t.
. 0
. 0
. 0
. 1
. 2
. 3
. «*
. 5
. 6
. 7
. 0
. 0
. 0
. 0
. 0
. 0
. 0
. 0
. 1
. 2
.3
. 4
. 5
. 0
. 0
PART
NAME
FUEL FILTER
POINTS
CONDENSER
CAP
ROTOR
M6CM ADVANCE
VACUUM ADVANCE
DISTRIBUTOR DKIV
DUAL DIAPHM DIST
SPARK DELAY VLV
MAG/OPT TRIGGERS
SPARK PLUGS
IGNITION WIRES
COIL
CAPACIT1VE 01SCH
BALLAST KESISTOR
EI CONTKOL CIRCT
IGN TIMING ADJ
TAC SMKUUU
TAC THERMOSTAT
TAC VAC MOTOR
TAC VAC MOSES
TAC FK6SH AIR IN
INTAKE MANIFOLD
TUHBOCHARUtH
RANK
32
10
45
9
B
86
89
16
9C
27
38
1
2
11
91
12
92
<*b
43
44
28
2V
93
9*
95
H C *™ ' """" ™
CI
0.147E-01
0.112t+00
0. 6576-02
0.22BE*00
0.231E+00
0.0
0.0
0.385t-01
0.0
0.172E-01
0.11AE-01
0.2fe5E*02
O.ti38t*01
0.69<»E-01
0.0
0.6V<»E-01
0.0
0.5^.0E-02
0.673E-02
0.673E-0?
0.169E-01
0.169E-01
0.0
0.0
0.0
RANK
46
47
48
49
50
27
22
51
36
52
53
54
55
56
"" 57
58
59
60
61
62
63
64
65
66
67
- CO 	
CI
0.0
0.0
0.0
0.0
0.0
0.385E-02
0.116E-01
0.0
0.143E-02
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
"™ NOX " — Mmm.
RANK CI
49
50
51
52
53
54
55
56
57
3
58
59
60
61
62
63
64
7
65
66
67
68
69
71
72
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1776*00
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.540E-01
0.0
0.0
0.0
0.0
0.0
0.0
0.0
"~""^™ S M 0 K C T • r _•
RANK CI
26
27
28
29
30
31
32
33
34
35
. 36
37
38
39
40
41
.. 42
43
44
45
46
47
48
49
50
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

-------
AUTOMOTIVE PARTS STUDY -  EPA  CONTRACT NO. 68-01-1957
    CRITICALITY INDEX RANKING  - LATE MODELS
PRINCIPAL
PART
CODE
2.
*• 2.
_ 6.
I- 1.
1.
6.
6.
2.
2.
1.
3.
3.
6.
6.
6.
6.
5.
3.
3.
2.
6.
6.
6.
5.
5.
5.
6.
9.
3.
3.
10.
2.
3.
3.
3.
1.
1.
1.
1.
1.
2.
1.
1 .
1.
4.
2.
3.
3.
1.
1.
0
0
2
4
6
1
1
1
2
10
3

-------
AUTOMOTIVE PARTS  STUDY -.EPA  CONTRACT NO. 68-OI-1957
    CRIT1CALITY  INDEX  RANKING - LATE MODELS
PRINCIPAL RANKING - hC
PART
CODE
6.
f 6'
^ 6.
ro 6.
t>.
6.
1.
•
•
•
•
•
•
6.
6.
2.
4.
4.
6.
1.
3.
6.
2.
1.
2.
2.
2.
3.
3.
2.
3.
3.
3.
2.
3.
3.
*.
3.
3.
10.
3.
12.
13.
10.
3.
2.
<•.
7.
3.
9.
6
4
5
4
5
3
2
3
1
5
9
0
1
1
7
7
0
0
4
11
0
8
0
7
0
PART
NAME
FUEL TANK/CAP
tVAP VPRLIG SEP
AI BYPASS/UVRTR
AI CHECK VALVES
EVAP VAPOR CONTR
Al AIK FILTER
METERING ROD1>
VAC BKK VALVE
IDLE STPSOLENOIO
ACCELERATOR PUMP
FLOAT AND VALVE
FUEL FUTEK
METERING JETS
AI MANIFOLD
InERMO VAC VALV
SPARK DELAY VLV
Fl STARTING VALV
FI IDLt ADJUST
UtCEL VALVt
IDLE ENRICHMENT
AIR CLEANER ELEM
EUR VAC AMP
COIL
GASKETS
BALLAST KtSlSTOR
RANK
26
27
28
29
30. .
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
^*f 	
nt> «•**—•—
CI
0.134E-01
0.125E-01
0.113E-01
0.827E-02
0.803E-02
0.792E-02
0.716E-02
0.653E-02
0.630E-02
0.623E-02
0.602E-02
0.431E-02
0.371E-02
0.335E-02
0.327E-02
0.299E-02
0.284E-02
0.283E-02
0.278E-02
0.261E-02
0.233E-02
0.229E-02
0.201E-02
0.201E-02
0.200E-02
(CONT*D)
RANK
90
88
14
25
89
26
4
6
28
29
5
32
34
24
128
69
20
37
38
39
9
99
40
41
42
- CO 	
CI
0.0
0.0
0.2U3E-01
0.827E-02
0.0
0.792E-02
0.143E*00
0.653E-01
0.630E-02
0.623E-02
0.120E+00
0.431E-02
0.371E-02
0.837E-02
0.0
0.0
0.142E-01
0.283E-02
0.278E-02
0.261E-02
0.466E-01
0.0
0.201E-02
0.201E-02
0.200E-02
RANK
97
95
102
101
96
100
32
. 33
28
35
.. 39
42
31
98
3
5
77 _
78
126
41
63
4
54
37
56
NOX 	
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.654E-01
0.299E-01
0.0
0.0
0.0
0.0
0.0
0.458E-01
0.0
0.0
0.0
RANK
75
73
80
79
74 .
78
21
22
17
24
.. 28 .
31
20
76
128
40
64
10
125
30
5
90
44
26
46
SMOKE 	
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.378E-02
0.0
0.0
0.155E-01
0.0
0.0
0.0
0.0

-------
AUTOMOTIVE PARTS STUDY -  EPA CONTRACT NO.  68-01-1957
    CRITICALITY INDEX RANKING  - LATE  MODELS
PRINCIPAL
PART
CODE
r
^ 6.
w 1.
1.
1.
1.
0.
3.
6.
6.
2.
2.
6.
5.
2.
6.
5.
5.
4.
6.
2.
to.
6.
6.
3.
3.
9.
3.
3.
3.
3.
1.
2.
1.
3.
5.
3.
3.
1.
6.
3.
1.
1.
12.
10.
3.
10.
3.
3.
4
6
2
2
V
3
10
3
0
1
2
0
• 4
5
i"
0
7
4
5
0
1
3
2
1
4
PART
NAME
C«OKE MECHANISM
POWER VALVES
CAT ACTIVE MEDIA
METERING RODS
FLOAT AND VALVE
VAC BRK VALVE
IDLE ADJUSTMENT
PCV FKSHAIK FLTH
AIR CLtANER ELEM
PCV VALVE
AI HOSES
SPARK PLUGS
VACUUM ADVANCE
AI BYPASS/OVRTR
VALVE LlFTER/SPR
IGNITION WIRES
AI PUMP/BELTS
VALVE SEALS
EXHAUST VALVES
FI STARTING VALV
HEAl RISER
MECn ADVANCE
ELEC ASSIST CHK.E
AI MANIFOLD
AI CHECK VALVES
RANK
4
5
3
32
36
33
10
13
46
14
23
1
90
28
17
2
22
24
25
42
6
89
57
39
29
RANKING - CO
- HC 	
CI
0.120E+00
0.1206*00
0.1906*00
0.716E-02
0.602E-02
0.653E-02
0.602E-01
0.506h-01
0.233E-02
0.427E-01
0.158E-01
0.348E*01
0.0
0.1136-01
0.280E-OI
0.237E*01
0.1S8E-01
0.146t-01
O.l46t-01
0.284E-02
0.1176*00
0.0
0.904E-03
0.335E-02
0.827E-02
RANK
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
?1
22
23
24
25
CO 	
CI
0.6026*00
0.602E+00
0.1906*00
0.143E*00
0.1206+00
0.653E-01
0.to02E-01
0.5066-01
0.4*6E-01
0.427E-01
0.3V5E-01
0.348E-01
0.3356-01
0. 2836-01
0.280E-01
0.237E-01
0.158E-01
0.146E-O1
0.146E-01
0.142E-01
0.117E-01
0.1126-01
0.904E-02
0.837E-02
0.827E-02
RANK
34
36
120
32
39
33
40
90 .
63
88
99
52
48
102
79
53
104
82
83
77
123
47
124
98
101
• NOX 	
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
— 	 SMOKE 	
RANK CI
23
25
119
21
28
22
29
6tt
5
66
77
42
37
80
1
43
82
2
3
64
122
36
123
76
79
O.O
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.155E-01
0.0
0.0
0.0
0.0
0.0
0.2806+00
0.0
0.0
0.l4toE+00
0. 146E+00
0.0
0.0
0.0
0.0
0.0
0.0

-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO.  68-01-1957
CRITICALITY INDEX RANKING - LATE MODELS
PRINCIPAL RANKING - CO
PART
CODE
f
•- i.
•£> 1.
3.
3.
1.
1.
1.
2.
2.
4.
6.
1.
2.
1.
2.
4.
1.
5.
*.
5.
b.
4.
6.
3.
9.
2.
3.
1.
1.
4.
2.
3.
3.
3.
13.
10.
3.
7.
3.
9.
3.
2.
1.
1.
2.
7.
7.
1.
3
0
1
5
3
4
0
2
I
1
2
0
4
11
0
7
0
0
3
2
3
0
2
0
2
PART
NAME
AI AIR FILTER
EFI INJECTORS
IDLE STPSOLENOIO
ACCELERATOR PUMP
TAC VAC MOTOR
TAC VAC hOSES
FUEL FILTER
THROTTLE DASHHOT
METERING JETS
CAP
ROTOR
FI lt)Lt ADJUST
DECEL VALVE
IDLE ENRICHMENT
COIL
GASKETS
bALLAST RESISTOR
FI PRES SENS/KEG
TnRlTL POS1TIONR
VALVE CAM LObES
VALVE GUIDES
PISTON RINGS
OSAL VAC HOSES
EFI TEMPSENS/SWH
PCV MUSES
RANK CI
31
61
3*
35
11
12
37
59
38
8
9
43
44
45
48
49
50
73
74
52
53
54
75
64
15
0.792E-02
0.360E-03
0.630E-02
0.623E-02
0.557E-01
0.555E-01
0.431E-02
0.3VOE-03
0.371 £-02
0.070E-01
O.t>70£-01
0.283t-02
0.276E-02
0.261E-02
0.201E-02
0.201E-02
0.200E-02
0.170E-03
0.170E-03
0.1'.6E-02
0.1*»feE-02
0.1<»t>t-02
0.1A5E-03
0.2A6E-03
0.383E-01
(CONT'D)
RANK
26
27
28
29
30
31
32
33
3<»
35
3o
37
38
39
<»0
41
42
43
44
45
46
47
48
49
50
- CO 	
CI
0.792E-02
0.719E-02
0.630E-02
0.623E-O2
0.557E-02
0.55 56-02
0.431E-02
0.396E-02
0.371E-02
0.335E-02
0.335E-02
0.283t-02
0.27BE-02
0.261E-02
0.201E-02
0.201E-02
0.200E-02
0.170E-02
0.170E-02
0.1H6E-02
0.146E-02
0.146E-02
0.145E-02
0.123E-02
0.112E-02
RANK
100
75
28
35
60
61
42
29
31
45
46
78
126
41
54
37
56
69
30
80
81
84
112
73
89
- NOX 	
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
- 	 SMOKE 	
RANK CI
78
61
17
24
51
52
31
18
20
34
35
10
125
30
44
2b
46
13
19
6
7
B
109
59
67
O.O
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.378E-02
0.0
0.0
0.0
0.0
0.0
0.119E-02
0.0
0.146E-01
0.146E-01
0.146E-01
0.0
0.0
0.0

-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
    CRITICALITV INDEX RANKING -  LATE  MODEtS
PRINCIPAL RANKING - NOX
PART
CODE
j, 6. *.
i b. 4.
•- 6.10.
01 6. 4.
2. 3.
6. 4.
2.11.
6. 4.
6. 4.
6. 4.
6. 7.
6. 4.
6. <..
6. 8.
6.5.
6. 5.
6. 5.
b. *>.
.6. 8.
b. 5.
b. b.
b. 4.
6. 6.
b. b.
4.10.

1
3
7
a
7
2
0
10
11
b
1
4
7
5
a
i
b
5
1
3
5
5
1
4
0

EGR
EGR
PART
NAME
VALVES
TMEKMO VALVE
THERMO VAC VALV
EGR VAC AMP
SPARK OtLAY VLV
EiiR
IGN
EGR
EGR
EGR
OSAC
EGR
EGR
fcSC
TCS
TCS
KS
TCS
ESC
TCS
SCS
EGR
SCS
SCS
EFI
HOSES/SEALS
TIMING ADJ
CARB SPACER
BACK.PK6S SEN
SPEED/TRANS
VAC ORIFICE
SOLENOID VLV
TIME DELAY
SPEED SNITCH
TfcMH SWITCH
VAC SOLENOID
TRANS SWITCH
TntKMO VALVE
ELtC MODULE
TIMt UtLAY
THtRMO VALVE
TEMP SxITCH
VACUUM SOLEN
SPEED SWITCH
TRIGGER SwCH
m m ^^ -r- .jf »^ L _M. J^
RANK CI
106
107
tO
47
41
Sb
51
113
114
110
58
108
111
63
65
66
69
71
77
78
80
10V
83
84
79
0.0
0.0
0.327E-02
0.?29E-02
0.299E-02
0.108E-02
0.11>bE-02
0.0
0.0
0.0
0.784E-03
0.0
0.0
0.261E-03
0.209E-03
0.192E-03
0.192E-03
0.1B9E-03
0.712E-04
0.592E-04
0.2266-04
0.0
0.752E-05
0.752E-05
0.273E-04
RANK
92
94
128
99
69
93
72
101
102
97
115
95
90
123
110
104
108
107
119
105
114
96
111
113
65
• CO 	
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.137E-04
RANK
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
- NOX 	
CI
0.212E«00
0.132E+00
0.654 £-01
0.458E-01
0.29VE-01
0.216E-01
O.l&bE-Ol
0.153E-01
0.149E-01
0.102E-01
0.7B4E-02
0.538E-02
0.523E-02
0.523E-02
0.418E-02
0.385E-02
0.385E-02.
0.377E-02
0.142E-02
0.1186-02
	 SMOKE 	
RANK CI
83
85
128
90
40
84
48
92
93
88
108
86
89
117
102
95
100
99
113
97
0.451E-03 107
0.150E-03 87
0.150E-03_J03
0.150E-03
0.137E-05
106
62
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

-------
AUTOMOTIVE PARTS STUDY  -  EPA  CONTRACT NO. 68-O1-1957
    CRITICAL!TV INDEX RANKING  - LATE  MODELS
PRINCIPAL RANKING - NOX tCfl
PART
CODE
1.
*• 1.
^ 1.
en 1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
2.
2.
2.
2.
2.
2.
2.
2.
1.
1.
2.
2.
2.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
*».
1.
2.
3.
3.
3.
3.
3.
3.
1
2
1
2
3
1
2
3
4
5
6
7
8
9
10
11
0
o"
0
1
2
3
5
6
PART
NAME
NEW CARB
REBUILT CARB
IDLE STPSOLENOID
THROTTLE UASHPOT
THRTTL POSITIONR
METERING JETS
MbTkKlNG RUDS
VAC BKK VALVE
CHOKE MECHANISM
ACCELERATOR PUMP
POWER VALVES
GASKETS
REBUILDING KITS
FLOAT AND VALVE
IDLE ADJUSTMENT
IDLE ENRICHMENT
FUEL FILTER
POINTS
CONDENSER
CAP
ROTOR
MECH ADVANCE
VACUUM ADVANCE
DISTRIBUTOR OK IV
DUAL UlApnM DIST
RANK CI
86
87
34
59
74
38
32
33
35
5
49
68
36
10
45
37
60
fal
b
9
«9
90
55
VI
0.0
0.0
0.630E-02
0.396E-03
0.170E-03
0.371E-02
0.716E-02
0.653E-02
0.1206*00
0.623E-02
0.120E»00
0.201E-02
0.0
0.602E-02
0.602E-01
0.261E-02
0.431E-02
0.393E-03
0.168E-04
0.670E-01
0.670E-01
0.0
0.0
0.111E-02
0.0
RANK
66
67
28
33
44
34
4
6
1
29
2
41
68
5
7
39
32
55
64
35
36
22
13
52
54
O»D)
CO 	
CI
0.0
0.0
0.630E-02
0.396E-02
0.170E-02
0.371E-02
0.143E+00
0.653E-01
0.602E+00
0.623E-02
0.602E»00
0.201E-02
0.0
0.120E*00
0.602E-01
0.261E-02
0.431E-02
0.393E-03
0.168E-04
0.335E-02
0.335E-02
0.112E-01
0.335E-01
0.111E-02
0.692E-03

RANK
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50

NOX —
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

RANK
15
16
17
18
19
20
21
22
23
24
„ 25
26
27
28
29
30
31
32
33
34
35
36
37
38
39

SMOKE 	
CI
0.0
0.0
0.0
0.0
o.o
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

-------
AUTOMOTIVE PARTS STUDY -  EPA  CONTRACT NO.  68-O1-1957
    CRITICALITY INDEX RANKING  - LATE MODELS
PRINCIPAL RANKING - SMOKE
PART
CODE
5.
J> 5.
:. 5-
^i *•
3.
5.
5.
5.
4.
4.
5.
*>.
<».
3.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
5.
2.
1.
1.
2.
<».
13.
<•.
•3.
3.
<».
1.
1.
2.
2.
2.
3.
3."
3.
3.
"3."
3.
1
*»
0
0
2
3
0
0
0
1
0
0
0
1
2
1
2
3
1
3
4
•>
6
PART
NAME
VALVE L1FTER/SPR
VALVE SEALS
EXHAUST VALVES
MFI VALVES
AIR CLEANER ELEM
VALVE CAM LUBES
VALVE GUIDES
P1S10N KINGS
f-i THROTTLE VALV
Fl IDLE ADJUST
HEAD GAbKETS
CAMbHAHTS
f-l PRES SENS/KEG
TUKBOCHARGtK
NtX CAKb
REBUILT GARB
IDLE blPSOLENOID
THhUTTLt DAbHPOT
THRTTL PUSITIONR
METERING JtTb
METERING RODS
VAC BKK VALVE
CHOKE MECHANISM
ACCELERATOR PUMP
POWER VALVES
RANK
17
24
25
100
46
52
53
54
99
43
62
66
73
95
86
b7
34
59
74
38
32
33
4
35
5
MT — — — — -r
nw —
CI
0.280E-01
0.1^.66-01
0.146E-01
0.0
0.233E-02
0.146E-02
0.1A6E-02
0.1<>6E-02
0.0
0.283E-02
0.3<.VE-03
0.207E-03
0.170E-03
0.0
0.0
0.0
0.630E-02
0.396E-03
0.170E-03
0.371E-02
0.716E-02
0.653E-02
0.120E*00
0.623E-02
0.120fc+00
RANK
15
18
19
81
9
45
46
47
80
37
56
57
43
76
66
67
28
33
4<»
3t
4
6
1
29
2

CO 	
CI
0.280E-01
0. 1^66-01
0.146E-01
0.0
0.466E-01
0.146E-O2
0.146E-02
0. 1A6E-02
0.0
0.283E-02
0.349E-03
0.207E-03
0.170E-O2
0.0
0.0
0.0
0.630E-02
0.396E-02
0.170E-02
0.371E-02
0.143E*00
0.653E-01
0.602E+00
0.623E-O2
0.602t+00

RANK
79
82
83
71
63
80
81
8*
70
73
86
87
69
65
26
27
28
29
30
31
32
33
34
35
36

NOX 	
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

RANK
1
2
3
4
.5
6
7
8
9
10
11
12
13
14
15
16
17
lb
19
20
21
22
23
24
25

SMOKE 	
CI
0.280E+00
0.146E+00
0.146E+00
0.708E-01
0.155E-01
0.146E-01
0.146E-01
0.1<»6E-01
0.388E-02
0.378E-02
0.349E-02
0.2076-02
0.119E-02
0.468E-0*
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

-------
AUTOMOTIVE PARTS STUDY -  EPA  CONTRACT NO.  68-O1-1957
    CRITICALITY INDEX RANKING  - LATE  MODELS
PRINCIPAL RANKING - SMOKE «CONT»D)
PART
CODE
1.
f 1.
^ 1.
00 1.
1.
1.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
3.
3.
3.
3.
3.
3.
3.
4.
1.
2.
3.
3.
3.
3.
3.
3.
3.
4.
5.
6.
7.
B.
*.
10.
11.
1.
1.
7
8
9
10
11
0
0
0
1
2
3
4
5
6
7
0
0
0
0
0
0
0
0
r
2
PART
XAME
GASKETS
REBUILDING KITS
FLOAT AND VALVE
IDLE ADJUSTMENT
IDLE ENRICHMENT
FUEL FILTER
POINTS
CONUl-NSEK
CAP
ROT OK
MECh ADVANCE
VACUUM ADVANCE
DISTRIBUTOR DRIV
DUAL DIAPHM D1ST
SPARK DbLAY VLV
MAG/OPT TRIGGERS
SPAKK PLUGS
IbNITION MIRES
COIL
CAPACITIVE DISCH
BALLAST RESISTOR
El CONTROL C1RCT
IGN TIMING ADJ
TAC SHROUD
IAC THERMOSTAT
RANK
49
88
36
10
<.{>
37
bO
81
a
V
89
90
55
VI
41
20
1
2
48
92
50
93
51
18
19
i*r 	
n^
CI
0.201E-02
0.0
0.602E-02
0.6026-01
0.261E-02
0.431E-02
0.393E-03
0.168E-04
0.670E-01
0.670E-01
0.0
0.0
0. 1116-02
0.0
0.299E-02
0.198E-01
0.3^86*01
0.2376*01
0.201E-02
0.0
0.200E-02
0.0
0.156E-02
0.2016-01
0.201E-01
RANK
41
68
5
7
39
32
55
64
35
36
22
13
52
54
69
58
12
16
40
70
42
71
72
73
74
- CO 	
CI
0.201E-02
0.0
0.1206+00
0.6026-01
0.261E-02
0.431E-O2
0.393E-03
0.168E-Ot
0.3356-02
0. 3356-02
0.1126-01
0.3356-01
0.1116-02
0.6926-03
0.0
0.1986-03
0.3486-01
0.2376-01
0.2016-02
0.0
0.200E-02
0.0
0.0
0.0
0.0
RANK CI
37
38
39
40
41
42
43
44
45
46
-...47
48
49
50
5
51
52
53
54
55
56
57
7
58
59
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.299E-01
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1566-01
0.0
0.0
	 SMOKE 	
RANK CI
26
27
28
29
^0
31
32
33
34
35
.36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

-------
AUTOMOTIVE PAKTS STUDY - EPA CONTRACT NO. 68-01-1957
    CKITICALITY INDEx RANKING - ALL MODELS
PRINCIPAL RANKING - HC
PART
CODE
2.
3> 2.
^ 5.
^o I"
1.
5.
5.
2.
2.
b.
6.
6.
2.
1.
3.
3.
2.
2.
b.
6.
b.
6.
5.
5.
5.
b.
1.
3.
3.
1.
1.
3.
'3.
9.
2.
10.
1.
3.
1.
1.
7.
9.
I.
1.
I.
2.
1.
1.
2,
0
0
1
4
b
*
5
2
1
2
1
1
0
10
3
4
0
0
1
3
2
2
2
3
0
PART
NAME
SPARK PLUGS
IGNITION HIRES
VALVE LIFTER/SPR
CHOKE MECHANISM
POWER VALVES
VALVE SEALS
EXHAUST VALVES
ROTOK
CAP
CAT ACTIVE MEDIA
tVAP CANISTER
HEAT RISER
POINTS
IDLE ADJUSTMENT
TAC VAC MOTOK
TAC VAC HOSES
COIL
BALLAST RESISTOR
PCV VALVE
PCV FRSHAIR FLTR
KCV HOSES
EVAP HOSES
VALVE CAM LOBES
VALVE GUIDES
PISTON RINGS
RANK
1
2
3
4
5
6
7
6
9
10
11
12
13
14
15
Ib
17
18
19
20
21
22
23
24
25
tjf- _ _, — — — .
nu ~ ™™-™
CI
0.300E+02
0.107E+02
0.873E+UO
0.531E+00
0.531E*00 ...
0.521E*00
0.521E*00
0.298E*00
0.295E-»00
0.1906+00
0.1
-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT  NO. 68-O1-1957
    CKITICALITY INDEX RANKING  - ALL  MODELS
PRINCIPAL RANKING - HC
PART
CODE
6.
•E- *"
f 2.
IV) 6.
o 2.
1.
3.
3.
1.
1.
6.
6.
2.
1.
1.
*.
I.
6.
6.
5.
6.
6.
6.
1.
I.
3.
3.
3.
2.
4.
3.
1.
1.
3.
3.
2.
?.
3.
t.
3»
2.
3.
2.
3.
*.
3.
3.
3.
2.
3.
7
2
5
3
0
3
1
2
5
9
6
<•
7
0
2
0
1
5
5
1
4
3
I
I
7
PART
NAME
AI PUMP/BELTS
AI HOSES
DISTRIbUTOR OKIV
EVAP FRSH AIR
MAG/OPT TRIGGERS
VAC BRK. VALVfc
TAC SnkOUO
TAC ThbRMOSTAT
ACCtLEKATOK PUMP
FLOAT ANU VALVE
Fufcu TANK/CAP
fcVAP VPKLIG SEP
SfAKK DELAY VLV
FUtL F1LTEK
MfcTEKlNli RODS
A1K CLtANER ELEM
METERING JETS
EVAP VAPOR CONTR
AI bVPASS/OVRTR
HEAD GASKtIS
AI CHECK. VALVES
AI AIR FILTER
AI MANIFOLD
IDLE S1PSOLENOIO
GASKETS
RANK
26
27
28
29
30
3\
32
33
3i
3$
36
37
3Q
3V
<*0
M
42
43
<*4
45
46
47
48
<*9
50
CI
0.433E-01
0.433E-OI
0.396E-01
0.357E-01
0.312E-01
0.271E-01
O.?fe86-01
0.268fc-01
0.2b6t-01
0.267E-01
0.249F-01
0.238E-01
0.202E-OI
0.191E-01
0.1856-01
0.167E-01
0.163E-01
0.1356-01
0.133E-01
0.124E-01
0.116E-01
0.107E-01
0.942E-02
0.938E-02
0.886E-02
ICONT'D)
RANK
19
14
58
90
62
13
76
77
23
<•
93
91
72
40
7
«
25
V2
22
29
31
34
27
20
50
CO 	
CI
0.433E-01
0.670E-01
0.111E-02
0.0
0.198E-03
0.858E-01
0.0
0.0
0.268E-01
0.535E+00
0.0
0.0
0.0
0.431E-02
0.370E+00
0.335E»00
0.163E-01
0.0
0.302E-01
0. 1246-01
0.116E-01
0.107E-01
0.144E-01
0.372E-01
0.201E-02
RANK CI
112
107
57
102
59
41
66
67
43
47
105
103
3
50
'"" 40
71
39
104
110
94
109
108
106
36
45
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.202EfOO
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
^ SMOKE " ™* m
RANK CI
82
77
38
72
.41 _..
22
49
50
24
28
75
73
40
31
21
8
20
74
80
12
79
78
76
17
26
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.140E-01
0.0
0.0
0.0
0.190E-02
0.0
0.0
0 0
0.0
0.0

-------
AUTOMOTIVE PARTS STUDY -  EPA CONTRACT NO.  68-01-1957
    CRITICALITY INDEX RANKING  -  ALL  MODELS
PRINCIPAL
PART
CODE
i.
*• i.
t^o *•
^ 1.
5.
5.
1.
3.
b.
1.
6.
6.
1.
b.
5.
5.
5.
2.
6.
1.
2.
b.
1.
2.
1.
3. 4
3. 6
1. 1
3. V
1. 4
1. 5
3. 2
2. 0
1. 1
3.10
9. 2
1. 3
3. 3
3. 2
1. 2
1. 3
2. 0
3. 4
3. 7
2. 1
5. 0
3. 5
3. 5
b. 0
3. 1
PART
NAME
CHOKE MECHANISM
POWER VALVES
VALVE LIFTtK/SPR
FLOAT AND VALVE
VALVE SEALS
EXHAUST VALVES
METERING RODS
AIR CLEANER ELEM
PCV VALVfc
IDLE ADJUSTMENT
CAT ACTIVE MEDIA
PCV FRSnAlH FLlR
VAC BRK VALVE
AI HOSES
VALVE CAM LOBES
VALVE GUIDES
PISTON RINGS
VACUUM ADVANCE
Al PUMH/BELTS
IDLE STPSOLEN01D
SHARK PLUG:*
AI bYPASS/DvRTR
ACCELEKAlOK PUMP
IGNITION WIRES
METERING JETS
RANK
4
5
3
35
b
7
40
41
19
14
10
20
31
27
23
24
25
VV
26
4V
1
t4
34
2
42
RANKING - CO
• HC 	
CI
0.531E*00
0.531E+00
0.873E*00
0.267E-01
. 0.521E»00
0.521E»00
0.1B5E-01
0.1b7E-01
0.b94E-01
0.810E-01
0.190E*00
0.027E-01
0.271E-01
0.<»33t-01
0.521E-01
0.521E-01
0.521E-01
0.0
0.433E-01
0.93dE-02
0.300E»02
0.133E-01
0.268E-01
0.107E*02
0.163E-01
RANK
1
2
3
4
5
b
7
a
9
10
11
12
13
14
15
Ib
17
Ib
19
20
21
22
23
24
25
CO 	
CI
0.266E+01
0.2666*01
O.B73E+00
0.535E*00
..0.521E + 00
0.5216*00
0.3706*00
0.335E*00
0.309E*00
0.2686*00
0.190E+00
0.171E«00
0.b5BE-01
0.670E-01
O.WIE-OI
0.521E-01
0.5216-01
0.451E-01
0.433E-01
0.372E-01
0.348E-01
0.302E-01
0.268E-01
0.237E-01
0.163E-01
RANK
42
44
87
47
90
91
40
71
96
<*a
122
98
41
107
88
89
92
56
112
36
60
110
43
61
39
NOX 	
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
- 	 SMOKE 	
RANK CI
23
25
2
28
5
6
21
8
66
29
119
68
22
77
9
10
11
37
82
17
42
80
24
43
20
0.0
0.0

0.211E+00
0.0
0.1?6P*00
0.1266*00
0.0
0.140E-01
0.0
0.0
0.0
0.0
0.0
0.0


0. 1266-01
0.126E-01
0.126E-01
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0




-------
CRITICALITY INDEX RANKING - ALL MODELS
PRINCIPAL RANKING - CO
PART
CODE
I'
i *>«
ro 4.
1 ^> 5.
to.
b.
6.
6.
6.
<•.
5.
1.
3.
3.
1.
6.
1.
2.
2.
4.
1.
6.
2.
2.
1.
3.
3.
12.
4.
10.
3.
10.
10.
3.
9.
5.
2.
1.
1.
4.
5.
2.
3.
3.
13.
3.
5.
3.
7.
3.
3
1
0
1
1
4
4
2
3
0
0
2
3
4
6
4
3
1
2
0
11
2
6
0
7
PART
NAME
MECM ADVANCE
AI MANIFOLD
FI STARTING VALV
HEAD GASKETS
HEAT RISER
AI CHECK VALVES
DECEL VALVE
ELEC ASSIST ChKE
AI AIR FILTER
EFI INJECTORS
CAMSHAFTS
THROTTLE OASHPOT
TAC VAC MOTOR
TAC VAC HOSES
FUEL F1L1EK
TCS CEC VALVE
THRTTL POSITIONR
CAP
ROTOR
FI IDLE ADJUST
IDLE ENRICHMENT
TCS VAC HOSES
DUAL DIAPHM DIST
COIL
GASKETS
RANK
98
48
62
45
12
46
57
65
47
81
51
73
15
16
3V
56
78
9
b
63
to 6
69
100
17
50
HC 	
CI
0.0
0.942E-02
0.284E-02
0.124E-01
0.1436*00
0.116E-O1
0.363E-02
0.262E-02
0.107E-01
0.360E-03
0.714E-02
0.674E-03
0.725t-01
0.724E-01
0.191E-01
0.425E-02
0.376E-03
0.295E*00
0.2986+00
0.283E-02
0.261E-02
0.165E-02
0.0
0.7l4t-01
0.886E-02
ICONT'D)
RANK
26
27
28
29
... 30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
- CO 	
Cl
0.150E-01
0.144E-01
0.142E-01
0.124E-01
... 0.117E-01
0.1166-01
0.113E-01
0. 108E-01
0.107E-01
0.719E-02
0.714E-02
0.674E-02
0.557E-02
0.555E-02
0.431E-02
0.425E-02
0.376E-02
0.33 56-02
0.335E-02
0.283E-02
0.261E-02
0.261E-02
0.212E-02
0.201E-02
0.201E-02
RANK
55
106
85
94
... 125 .
109
128
126 .
108
83
95
37
68
69
50
114
38
53
54
86
49
113
58
62
45
- NOX 	
CI
0.0
0.0
0.0
0.0
. 0.0 ... .
0.0
0.0
0.0
0.0
0.0
0.0 .
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
RANK
36
. .76
64
12
122
79
125
..123 ..
78
61
13
18
51
52
31
98
. 19
34
35
4
30
96
39
44
26
SMOKE 	
CI
0.0
0.0
0.0
0.190E-02
0.0 ..
0.0
0.0
0.0
0.0
0.0
0.190E-02
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.126E*00
0.0
0.0
0.0
0.0
0.0

-------
AUTOMOTIVE PARTS STUDY -  EPA  CONTRACT NO. 68-01-1957
PRINCIPAL
PART
CODE
3> 6. 4.
i 6. 4.
™ 2. 3.
w 6. 4.
6.10.
6. 4.
6. 5.
2.11.
6. 5.
6. 5.
6. 4.
t>. 5.
6. 7.
6. 4.
6. 
-------
CRITICAL1TY INDEX
RANKING - ALL MODELS
PRINCIPAL RANKING - NOX
PART
CODE
I"
i 6.
6.
6.
ro 6. 7.
-^ 6. 6.
6. 4.
6. 4.
8. 1.
4.10.






. 1.
. 1.
. 2.
. 2.
. 2.
. 3.
. 3.
. 3.
. 3.
. 3.
. 3.
. 3.
. 3.
. 3.
. 3.
. 3.
. 4.
1
4
5
5
9
12
0
0
1
2
1
2
3
1
2
3
<»
5
6
7
8
9
10
11
0
PART
NAME
SCS VACUUM SOLEN
SCS SPEbO SWITCH
OSAC TEMP SENSOR
SCS ThiERMO VALVE
EGR VAC REDUCER
EGR CHECK VALVE
DISTR VACUUM VLV
EFI TRIGGER SHCH
NEW CARb
REBUILT CARB
IDLE STPSOLENOID
THROTTLE DASHHOT
THkTTL POS1TIONR
METERING JETS
METERING ROOi
VAC 6KK VALVE
CnOKE MECHANISM
ACCELERATOR PUMP
POWER VALVES
GASKETS
REBUILDING KITS
FLOAT AND VALVE
IDLE ADJUSTMENT
IDLE ENRICHMENT
FUEL FILTER
RANK
84
85
76
66
121
12*
92
93
95
96
49
73
78
42
tO
31
4
3*
5
50
97
35
14
66
39
(CONT'D)
- HC 	 	
CI RANK
0.223E-03
0.223E-03
0.432E-03
0.212E-03
0.0
0.0
0.430E-04
0.273E-04
0.0
0.0
0.938E-02
0.674E-03
0.376E-03
0.163E-01
0.185E-01
0.27IE-01
0.5316*00
0.268E-01
0.531E+00
O.B86E-02
0.0
0.267E-01
0.810E-01
0.261E-02
0.191E-01
113
115
120
116
103 _
106
133
6d
69
70
20
37
42
25
7
13
1
23
2
50
71
4
10
46
40
• CO 	
CI
0.0
0.0
0.0
0.0
0.0
RANK
26
27
28
29
.. 30...
0.0 31
0.0 32
0.137E-04 33
0.0
0.0
0.372E-01
0.674E-02
0.376E-02
0.163E-01
0.370E*00
0.85bE-01
0.266E*01
0.268E-U1
0. 2666+01
0.201E-02
0.0
0.535E*00
0.26dE+00
0.261E-02
0.431E-O2
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
NOX —
CI
RANK
0.447E-02 103
0.447E-02 106
0.432E-02 112
0.423E-02 107
0.181E-02 _. 91 .
0.316E-03 94
0.430E-04 133
0.137E-05 62
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
15
16
17
10
19
20
21
22
23
24
25
26
27
28
29
30
31
SMOKE 	
CI
0.0
0.0
0.0
0.0
0-0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

-------
AUTOMOTIVE PARTS  STUDY  - EPA CONTRACT NO. 68-O1-1957
CRITICALITV INDEX RANKING - ALL MODELS
PRINCIPAL RANKING - SMOKE
PART PART
CODE NAME
4. 5. 0 MFI VALVES
i 5. I. I VALVE LIFTER/SPR
ro 4. 4. 0 FI THROTTLE VALV
01 4.13. 0 FI IDLE ADJUST
5. I. 4 VALVE SEALS
5. 1. 5 EXHAUST VALVES
4. 3. 0 FI PRES SENS/KEG
3. 2. o AIR CLEANER ELEM
5. 1. 2 VALVE CAN LOBES
5. 1. 3 VALVE GUIDES
5. 2. 0 PISTON KlNbS
5. 4. I HfcAU GASKETS
5. 5. 0 CAMSHAFTS
3. 4. 0 TuRBOCHAKGER
. 1. 1 NEW CAKb
. 1. 2 REbUKT CARB
. 2. t IDLb STPSOLENOID
. 2. 2 ThRUTTLt DASHPQT
. 2. 3 TnKTTL POSITIONR
. 3. 1 METERING JbTS
. 3. 2 METEKING RODS
. 3. 3 VAC BRK VALVE
. 3. 4 CHOKE MECHANISM
. 3. 5 ACCELEKAlOK PUMP
. 3. 6 POWER VALVES
RANK
109
3
108
63
b
7
90
41
23
24
25
45
51
104
95
96
49
73
78
42
40
31
4
34
5
HC 	
CI
0.0
0.873E+00
0.0
0.283E-02
0.521E+00
0.521E»00
0.170E-03
0.r67E-01
0.521E-01
0.521E-01
0.521E-01
0.124E-01
0.714E-02
0.0
0.0
0.0
0.938E-02
0.674E-03
0.376E-03
0.163E-01
0.165E-01
0.271E-01
0.531E+00
0.26bE-01
0.531E»00
RANK
84
_.. 3
83
45
5
6
54
8
15
16
17
29
36
7V
69
70
20
37
42
25
7
13
1
23
2
CO 	
CI
0.0
0.873E+00
0.0
0.283E-O2
0.521E+00
0.521E*00
0.170E-02
0.335E*00
0.521E-01
0.521E-01
0.521E-01
0.1?<,E-01
0.714E-02
0.0
0.0
0.0
0.372E-01
0.674E-O2
0.376E-O2
0.163E-01
0.370E+00
0.858E-01
0.266E*01
0.268E-01
0.2&6E+01
RANK
79
87
78
86
90
91
77
71
88
89
.. 92
94
95
73
34
35
36
37
38
39
40
41
42
43
44
- NOX 	
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
RANK
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17 ._.
18
19
20 „
21
22
23
24
25
SMOKE 	
CI
0.253E+01
0.211E+00
0.129E»00
0.126E*00
0.1?*,F*nn
0.126E+00
0.398E-01
0.140E-01
0.126E-01
0.126E-01
0.126E-01
0.190E-02
0.190E-02
0.187E-03
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

-------
AUTOMOTIVE PARTS STUDY  -  EPA  CONTRACT NO. 68-01-1957
    CRITICAL1TY INDEX  RANKING  - ALL  MODELS
PRINCIPAL RANKING - SMOKE
PART
CODE
f i:
fNJ 1.
« 1.
1.
1.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
3.
3.
3.
3.
"3.
3.
3.
*.
1.
2.
3.
3.
3.
3.
3.
3.
3.
4.
S.
6.
7.
0.
9.
10.
11.
1.
1.
7
8
9
10
11
0
0
0
1
2
3
*
5
6
7
0
0
6"
0
0
0
0
0
2
PART
NAME
GASKETS
REBUILDING KITS
FLOAT AND VALVE
IDLE ADJUSTMENT
IDLE ENRICHMENT
FUEL FILTER
POINTS
CONDENSER
CAP
RUTOR
MECM ADVANCE
VACUUM ADVANCE
DISTRIBUTOR DKlV
DUAL DIAPhM DIST
SPARK DELAY VLV
MAG/OPT TRIGGERS
SPAKK PLUGS
IGNITION HIRES
COIL
CAPACITIVE DISCH
BALLAST RESISTOR
El CONTROL CIRCT
IGN TIMING ADJ
TAC ShRUUO
TAC THERMOSTAT
RANK
50
97
35
14
66
39
13
53
9
8
98
99
28
100
30
30
1
2
17
101
18
102
52
32
33
HC 	
CI
0.8866-02
0.0
0.267E-01
0.810E-01
0.261E-02
0.191E-01
0.112E+00
0.658t-02
0.295E+00
0.29BE+00
0.0
0.0
0.396E-01
0.0
0.202t-01
0.312E-01
0.300E+02
0. 1076+02
0.7146-01
0.0
0.714E-01
0.0
0.695E-02
0.268E-01
0.268E-01
»CONT»D)
RANK
50
71
4
10
46
40
60
67
43
44
26
18
58

-------
               Appendix B




CRITICALITY INDEX INPUT PARAMETER VALUES

-------
EMISSION INCREASE FACTORS
— 	 GASOLINE 	 	 DIESEL (SMOKE > 	 •
PART
NAME
NEW CAKB
REBUILT CARB
IDLE STPSOLENOID
THROTTLE DASHPOT
CD THRTTL POSITIONR
i METERING JETS
^ METERING RODS
VAC BRK VALVE
CHOKE MECHANISM
ACCELERATOR PUMP
POWER VALVES
GASKETS
REBUILDING KITS
FLOAT AND VALVE
IDLE ADJUSTMENT
IDLE ENRICHMENT
FUEL FILTER
POINTS
CONDENSER
CAP
ROTOR
MtCH ADVANCE
VACUUM ADVANCE
DISTRIBUTOR OKIV
DUAL U1APHM DIST
SPARK DELAY VLV
MAG/OPT TRIGGERS
SPARK PLUGS
IGNITION MIRES
COIL
CAPAC1TIVE D1SCH
BALLAST HES1STUK
£1 CONTKUL CJRCT
lUN T IMINO AOJ
1 AC SriHOUU
TAG ThEKMOSIAT
EVAP
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
"o.o
— PRE-1975 —
HC CO NOX
0.0
0.0
0.1
0.1
0.1
0.1
0.1
0.1
2.0
0.1
2.0
0.1
0.0
0.1
0.1
0.1
0.1
1.0
1.0
2.0
2.0
0.0
0.0
1.0
0.0
0.1
10.0
10.0
10.0
1.0
0.0
1.0
0.0
0.1
0.1
O.I
0.0
0.0
1.0
1.0
1.0
0.1
2.0
(J.I
10.0
0.1
10.0
0.0
0.0
2.0
1.0
1.0
0.0
0.0
0.0
0.0
o.o
0.1
0.1
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
— POST-1975 —
HC CO NOX
0.0
0.0
1.0
0.
0.
0.
0.
0.
2.0
0.1
2.0
0.1
0.0
0.1
1.0
1.0
0.1
0.1
0.1
2.0
2.0
0.0
0.0
0.1
0.0
0.1
10.0
10.0
10.0
0.1
0.0
0.1
0.0
0.1
1.0
1.0
0.0
0.0
1.0
1.0
1.0
0.1
2.0
1.0
10.0
0.1
10.0
0.1
0.0
2.0
1.0
1.0
0.1
0.1
0.1
0.1
0.1
1.0
1.0
0.1
1.0
0.0
0.1 ;
0.1
0.1
0.1
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
PRE-197*
ACCEL LUG
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
	 POST-197* 	
ACCEL LUG PEAK
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
... o.o
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
PROBABILITY
• . FACTORS
- EARLY
FAIL
0.0
0.0
0.10
0.10
0.10
0.10
0.30
-.0.30
0.30
0.30
0.30
0.10
0.0
0.30
0.90
0.10
0.10
0.50
0.10
0.30
0.30
0.10
0.30
0.10
0.30
0.50
0.10
0.70
0.30
0.10
0.0
0.10
0.0
0.70
0.10
0.10
NO
REPL
0.0
0.0
0.50
0.50
0.50
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.0
0.90
0.30
0.90
0.50
0.10
0.10
0.50
0.50
0.50
0.50
0.50
0.90
0.90
VOLUME
FACTORS
72-7* 75
0.77077 0.22290
0.76920 0.22290
0.6172* 0.12593
0.055*0 0.07926
0.0*121 0.03392
1.3993* O.*1207
O.*1995 0.26506
0.76110 0T2*17%
0.76110 0.222VO
0.76110 0.230B1
0.76110 0.22290
0.76110 0.22290
0.76738 0.22290
0.76738 0.22290
0.77077 0.22290
0.0 0.02905
2.9*968 0.8629*
2.23211 0. 07656
0.65609 0.01679
0.75877 0.22336
0.77077 0.22336
0.77077 0.22336
0.77077 0.22336
0.77077 0.22228
0.052V5 0.00256
0.38332 0.06637
0.10 0.11*09 0.197B5
0.1037.8603* *. 90785
O.bO 5.5B569 1.57B53
0.90
0.0
0.90
0.0
0.10
0.90
0.90
0.77077 0.22336
0.0 0.0
0.77077 0.22197 	 	
O.M-.09 0.20u*b
0.77077 0.22228
0.7*813 0.22336
0.7*813 0.?2336

-------
EMISSION INCREASE FACTORS
	 GASOLINE 	 	 DIESEL 1 SMOKE I 	
PART
NAME
TAC VAC MOTOR
TAG VAC MOSES
TAC FRESH A1K IN
AIR CLEANER ELEM
co INTAKE MANIFOLD
' TURtOCMARlitR
SUPERCHARGER
MF1 ACCUMULATOR
Fl hi PRES PUMP
FI PRES StNS/RtG
FI THRUTTLE VALV
MFI VALVEi
EFI AlK SbNS/SWn
EF1 TEMPSF.NS/SWM
FI DIST MANIFOLD
EFI INJECTORS
EFI TKliilitR SwCH
EFI CONTROL CIRL
FI STARTING VALV
	 Fl IDLE ADJUST
VALVt LlFlER/SPR
VALVE CAM LUbES
VALVE OUIUES
VALVE SEALS
EXHAUST VALVtS
PISTON RINGS
PISTON/RODS
hitAD GASKtTS
_ CAMSHAFTS.
PCV VALVE
PCV MOSES
_ PCV FR^HAiK FLTR
PCV OIL SbPARATR
tVAP CANlSTtR
EVAP MOSES
tVAP M^n AIR
EVAH
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
10.0
0.0
0.0
10.0
10.0
2.0
— PRE-1975 —
MX CO NOX
0.1
0.1
0.1
0.1
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
1.0
1.0
0.0
0.1
2.0
0.0
1.0
0.1
1.0
1.0
1.0
1.0
1.0
1.0
0.0
1.0
1.0
0.1
0.1
0.1
0.0
0.0
0.1
0.0
0.0
0.0
0.1
2.0
0.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
5.0
5.0
0.0
2.0
0.1
0.0
5.0
1.0
1.0
1.0
1.0
1.0
.0
.0
.0
.0
.0
.0
0.0
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
u.o
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
— POST-1975
MC CO
1.0
1.0
0.1
0.1
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
1.0
1.0
0.0
0.1
2.0
0.0
1.0
1.0
0.1
0.1
0.1
0.1
0.1
0.1
0.0
0.1
0.1
1.0
0.1
1.0
0.0
0.0
0.1
0.0
0.1
0.1
0.1
2.0
0.0
0.0
0.0
... o.o
0.0
1.0
0.0
0.0
5.0
5.0
0.0
2.0
1.0
0.0
5.0
1.0
0.1
0.1
U.I
0.1
0.1
0.1 .
0.0
0.1
0.1
1.0
0.1
1.0
0.0
0.0
0.1
0.0
— PRE-197*
NOX ACCEL LUG
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0 ""
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
0.0
1.0
0.0
0.1.
0.0
1.0
1.0
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.0
1.0
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
.. 0.1
0.0
0.1
0.1
1.0
0.0
0.0
0.0
0.0
. 0.0
0.0
0.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.0
1.0
1.0
0.0
0.0
0.0
0.0
0.0
0.0
o.n
PROBABILITY
	 FACTORS
	 POST-1974 	 EARLY
ACCEL LUG PEAK FAIL
0.0
0.0
0.0
1.0
0.0
1.0
0.0
o.l
0.0
1.0
2.0
1.0
0.0
0.0
0.0
0.0
o.o ...
0.0
0.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.0
1.0
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.1 .
0.0
0.1
0.1
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
1.0
1 .0
1.0
1.0
1.0
i.o_
0.0
1.0
i.o
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
0.0
1.0
0.0
0.1
0.0
1.0
2.0
1.0
O.P
0.0
0.0
0.0
o.o ..
0.0
0.0
2.0
1 .0
1.0
1.0
1.0
1.0
1.0
0.0
1.0
i.o ,
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.30
0.30
0.30
0.10
0.0
0.10
0.0
0.01
0.0
0.30
0.50
2.00
0.30
0.30
0.0
0.50
0.30
0.0
0.50
0.50
0.30
0.01
0.01
0.10
0.10
0.01
0.0
0.01
0.01
0.30
0.10
0.10
0.0
0.30
0.10
0.10
NO
REPL
0.90
0.90
0.90
0.50
0.0
0.30
0.0
0.90
0.0
0.90
0.90
0.90
0.10
O.VO
0.0
0.90
0.10
0.0
0.90
0.30
0.50
0.90
0.90
0.90
0.90
O.VO
0.0
0.90
0.90
0.30
0.50
0.70
0.0
0.50
0.50
O.M)
VOLUME
FACTORS
72-74 75
0.62497
0.62443
0.0
2.SB371
0.77077
0.0
0.0
0.0
0.0
0.0
0.0... .
0.0
0.0
0.0
0.0
0.0
0.0 	
0.0
0.0
0.0
5.63017
5.63017
5.63017
5.63017
5.63017
5.63017
5.63017
1.33921
0.77077
2.95964
0.77077
1.71585
0.00035
0.7V021
0.76970
/.ivm
0.20613
0.20568
0.00723
0.^6598
0.22793
0.00223
0.0
0.0
0.00676
0.00630
0.00630
0.03933
O.OOU
0.00091
0.00630
0.00799
0.000'S'/SQ

-------
EMISSION INCREASE
	 GASOLINE 	
PART
NAMt
EVAP VPRLIG SEP
EVAP VAPOR CON1R
FUEL TANK/CAP
AI MANIFOLD
AI HOSES
1° AI AIR FILTER
(ji AI CHECK VALVES
Al BYPASS/DVK1R
Al GULP VALVES
AI PUMP/BtLTS
EGR VALVtS
EGR HOStS/SEALS
EGR THfcKMU VALVfc
EGR SOLENOID VLV
EGR TEMP SwllCn
EGR SPEED/TKANS
EGH TIME DELAY
ftGH VAC AMP
EGR VAC REDULEK
EtR CARB SPACER
EGR 6ACKPRES SEN
EGR CHECK VALVE
TCS VAC SULEN010
TCS VAC HOSES
TCS TIME DELAY
TCS CEC VALVE
TCS iHEkMO VALVE
TCS TRANS SWITCH
TCS RbVERSt RtLY
TCS TfcMP SWITCH
SCS VACUUM iULEN
SCS VACUM LlNt
StS 11*1 UtLAY
SCS St'ttl) SwllLH
SCS ThfckMU VALVE
OSAC VAC OK1HLE
EVAP
2.0
2.0
2.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
— PRE-1975 —
HC CO NOX
0.0
0.0
0.0
1.0
1.0
0.1
0.1
0.1
0.1
1.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.
0.
0.
2.0
0.
0.
0.
0.
0.
0.
0.
0.
0.1
0.1
0.0
0.0
0.0
1.0
1.0
0.1
0.1
0.1
0.1
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0*0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
2.0
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
o.o
0.0
0.0
0.0
o.o
0.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
1.0
1.0
1.0
0. 1
2.0
"o.o
2.0
0.0
2.0
2.0
2.0
2.0
2.0
O. 0
2.0
2.0
?.o
1.0
— POST-1975 —
HC CO NOX
0.0
0.0
0.0
2.0
2.0
S rO
1.0
2.0
2.0
2.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.1 "
0.0
0.0
0.0
0.0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.
0.
0.
0.
0.
0.
0.1
0.0
0.0
0.0
5.0
5.0
1.0
1.0
5.0
5.0
2.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
o.c
0.0
"o.o
0.0
0.0
0.0
0.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
1.0
1.0
1.0
0.1
2.0
0.0
2.0
0.0
2.0
2.0
2.0
2.0
2.0
0.0
2.0
2.0
2.0
1.0
FACTORS
	 DIES
PHE-197*
ACCEL LUC
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0 "
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
EUS
ACCE
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
MOKE) —
PROBABILITY
— 	 FACTORS
POST-197* —
L LUG PEAK
0.0
0.0
0.0
0.0
0.0
0.0
o.o .
o.o
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0 •
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
- EARLY
FAIL
0.10
0.10
0.10
0.01
0.10
0.10
0.10
0.10
0.10
0.10
0.70
0.10
0.30
0.10
0.10
0.10
0.10
0.30
0.30
0.30
0.70
0.30
0.10
0.10
0.10
0.10
0.30
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.30
O.JO
NO
REPL
0.90
0.90
0.90
0.90
0.70
0.70
0.50
0.50
0.50
0.70
0.70
0.50
0.90
0.90
O.VO
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.50
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.50
0.9U
O.VO
0.90
O.VU
VOLUME
FACTORS
72-7* 75
0.75531
0.36345
0.76706
0.67**2
0.39273
0.39667
0.60629
0.39273
0.0
0.39273
0.527V9
0.50239
0.37807
0.23601
0.13025
0.0
-------
EMISSION INCREASE FACTORS
	 GASOLINE 	 	 DIESEL (SMOKE) 	
PART
NAME
OSAC VAC HOSES
OSAC THERMO VALV
m OSAC VAC BYPASS
i OSAC TEMP SENSCK
0^ ESC ELEC MODULt
ESC HOSES
ESC VAC VALVES
ESC TEMP SWITCH
ESC SPEtO SWITCH
CAT BODY
CAT ACTIVE MEDIA
CAT INtKTMEDlA
CAT SMELL
HEAT RISER
ELEC ASSISl CHKE
STAGED PULLDOWN
DfcCEL VALVE
D1ST VACDtCL VLV
01ST START SULtN
THERMO VAC VALV
CUOLING iMtRMST
tLfcCTRlCAL SYSTM
HIGH PERF EXnAST
EXHAUST MANlhOLD
D1STK VACUUM VLV
EVAP
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
— PRE-1975 —
HC CO NOX
0.1
0.1
0.1
0.1
0.1
O.I "
0.1
0.1
0.1
0.0
0.0
0.0
0.0
0.1
0.1
0.1
0.1
0.1
1.0
0.1
0.0
0.0
0.0
0.0
0.1
0.1
0.0
0.0
0.0
0.0
""0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.1
1.0
0.0
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
1.0
1.0
2.0
0.0
2.0
2.0
2.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
2.0
0.0
2.0
0.0
0.0
0.0
0.0
0.1
— POST-1975 —
HC CO NOX
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
2.0
0.0
0.0
1.0
0.1
0.1
1.0
0.1
1.0
0.1
0.0
0.0
0.0
	 o.o
0.1
1.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
0.0
0.1
2.0
0.0
0.0
0.1
1.0
1.0
1.0
0.0
1.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
1.0
1.0
2.0
0.0
2.0
2.0
2.0
0.0
, 0.0
0.0
0.0
0.0
0.0
0.0
0.0
2.0
0.0
2.0
0.0
0.0
0.0
0.0
0.1
PROBABILITY
	 FACTORS
PRE-1974 	 POST-1974 	 EARLY
ACCEL LUG ACCEL LUG PEAK FAIL
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.10
0.30
0.30
0.10
0.10
0.10
0.10
0.10
0.10
0.01
0.50
0.0
0.0
0.70
0.10
0.30
0.30
0.30
0.10
0.30
0.0
0.0
0.0
0.0
0.30
NO
REPL
0.50
0.90
0.90
0.90
0.90
0.50
0.90
0.90
0.90
0.90
0.90
0.0
0.0
0.90
0.90
0.90
0.90
0.90
0.50
0.90
0.0
0.0
0.0
0.0
0.90
VOLUME
FACTOKS
72-74 75
O.OU529
0.0
0.04801
0.04801
0.03996
0.03996
0.03996
0.03996
0.03996
0.0
0.0
0.0
0.0
0.41057
0.1V01S
0.06349
0.03164
0.00941
0.01556
0.0b051
0.76763
0.77077
0.04425
1.33921
0.00159
0.02905
0.0
0.0
0.0
0.00791
0.0
0.0
0.0
0.02905
0.21114
0.21114
0.21114
0.21114
0.16552
0.10046
0.0
0.01026
0.0
0.00359
0.12116
0.22921
0.22921
0.0
0.36735
0.0

-------
                                   ;c-.c: irjiCAL REPOKT DATA
                            ,/'/.•<:•: nm! /•;•_•; .•.•f//r«:.v <>n /'V ri  rr-- I; /.>',• i-
   ~340/2-76-q01_
 • : 1 1 1 1  ••••.•) sus'i i run
    Effect of Automotive Parts on  Vehicle and Engine
    Emissions
    Phase I - Original Equipment                   _
    Richard R.  Carlson
 . PEH(-O:N98«ING AGENCY CODE
 I j. SUPPLEMENTARY NOTTS
 16. ABSTRACT ,
           This final report documents  the  methodology and results of Phase  I  of the
 Investigation of the Effect of Automotive  Parts on Vehicle and Engine  Emissions.
 This  study was performed for the Environmental  Protection Agency, Office of Mobile
 Source  Enforcement, under Contract No.  68-01-1957.  The primary objective of  this
jstudy was  to identify engine and emission  control  system components which are critical
jin  causing excessive emissions of one  or more regulated pollutants.  Phase  I  of the
 study investigated the emission-criticality of original equipment installed by the
 engine  or  vehicle manufacturers.
           A computer model was developed to calculate and rank-order an  index repre-
jsenting the criticality of each component  type.  Separate rankings were  developed for
•HC, CO, NOX and smoke (heavy-duty diesel engines)  emissions and for pre-catalyst-
fequipped and catalyst-equipped vehicles.   The index for each component type was
[calculated from the product of four  factors representing the emission  increase resulting
jfrom  a  component failure, the probability  of component failure, the probability of
 component  repair, and the sales volume  of  the component.
           The values of these factors were established based on data obtained from a
 search  of  technical literature and engineering  analysis of system and  component design
 or operating characteristics.  The study was performed without emission  or  performance
 testing.   However, a series of tests on 25 of the  most emission-critical components was
 Fscommendod to develop or refine data on emission
                     »ase  and  symptoms of fail in
 7.
                  or T.c
woFius AND DOCUMENT ANALYSIS

           >. ID(;N ririE-HS/OHLN ENDLO .IT HMS
Cnr.ATI In-ld/dronp
   Ul'r-^iUUl !'..••; STATfcWEWl
   Unlimited
           19. SSCUHITY CLASS I This

           ___ Unclassified
           20       ""
                                                                          21. NO. OF
                                                  Unclassified
 EPA Fijr.n ??:0-l (9-73)

-------