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
-------
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
-------
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
-------
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
-------
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.
-------
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.
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
Misfireplugs
Misfirewiring
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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,
3-27
-------
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
3-28
-------
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.
3-29
-------
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
3-30
-------
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.
3-31
-------
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.
3-32
-------
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
-------
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
3-34
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
3-40
-------
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.
3-41
-------
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
3-42
-------
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
3-43
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
REFERENCES
2,
3,
4.
5,
6,
8,
9,
10,
11
12,
13
Ryan, T.W., et al, "Extension of the Lean Misfire Limit
and Reduction of Exhaust Emissions of a SI Engine by
Modifications of the Ignition and Intake Systems," SAE
740105, February 25 - March 1, 1976.
Lichty, Lester C., Combustion Engine Processes, McGraw -
Hill Book Company, 1967.
Toboldt, U.K. and L. Johnson, Automotive Encyclopedia,
Goodheart - Willcox Company, 1975.
Bentley, D.R. and D.J. Schweibold, "Questor Reverter
Emission Control System Total Vehicle Concept," SAE
730227, January 8-12, 1973.
Holt, E.L., et al, "Control of Automotive Sulfate
Emissions," SAE 750683, June 3-5, 1975.
Gunderson, J.A., and O.K. Lawrence, "Control of Refueling
Emissions with an Activated Canister on the Vehicle,"
SAE 751181, October 13-17, 1975.
Matsumoto, et al, "Reliability Analysis of Catalytic
Converter as an Automotive Emission Control System,"
SAE 750178, February 24-28, 1975.
Wyczalels, F.A., et al, "EFI Prechamber Torch Ignition
of Lean Mixtures," SAE 750351, February 24-28, 1975.
Wilson, R.P., et al, "Emissions Study of a Single-
Cylinder Diesel Engine," SAE 740123, February 25 -
March 1, 1974.
Lang, R.J . , et al ,
System Performance,
1974.
"Factors Affecting Dual Catalyst
" SAE 740252, February 25 - March 1,
Harrington, J.A., et al, "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," SAE
740188, February 25 - March 1, 1974.
Panzer, J., "Idle Emissions Testing - Par-l)- II," SAE
740133, February 25 - March 1, 1974.
West, D.T., et al, "A
Union 76 Fuel Economy
1975.
Technical Report of
Tests," SAE 750670,
the 1975
August 11-14
R-l
-------
14 Carr, Alexander, "An Over-the-Road Fuel Economy Test,"
SAE 750726, August 11-14, 1975.
15. National Academy of Sciences, "Report by the Committee
on Motor Vehicles Emissions," November 1974.
16. Final Report, Volume IV, CRC-APRAC-CAPE-13-68, July
1972 "A Study of Mandatory Engine Maintenance for
Reducing Vehicle Exhaust Emissions."
17. "Evaluation of CVS Test Procedures," Final Report, ARB
Contract 4-726, March 11, 1976.
18. Pachernegg, S.J., "Efficient and Clean Diesel Combustion,"
SAE 750787, September 8-11, 1975.
19. Mayo, J., "Effect of Engine Design Parameters on Combus-
tion Rate in Spark Ignited Engines," SAE 750355, February
24-28, 1975.
20. Gupta, R.K. and Graiff, L.B., "Effect of Exhaust Gas
Recirculation and Ignition Timing on Fuel Economy and
Exhaust Emissions of Several 1973 Model Cars," Combustion
Inst. , March 26-27 , 1974.
21. Morgan, C.R., S.S. Hetrick, "Trade-Offs between Engine
Emission Control Variables, Fuel Economy, and Octane,"
SAE SP-395, Paper 750415, January 1975.
22. Kaneko, Y., et al, "Effects of Exhaust Gas Recirculation
and Residual Gas on Engine Emissions and Fuel Economy,"
SP-395, Paper 750414, January 1975.
23. McGowin, C.R., et al , "Emissions Control of a Stationary
Two-Stroke Spark-Gas Engine by Modification of Operating
Conditions," Inst. of Gas Technology, Chicago, June 5-7,
1972.
24. Maringer, A., et al, "Automotive Diagnosis as a Feature
of Modern Checkout Systems," International Symposium on
Automation of Engine Test: Performance, Emission, and
Diagnosis, London, England, September 25-27, 1974.
25. Spilski, R.A., and W.D. Creps, "Closed Loop Carburetor
Emission Control System," SAE 750371, February 24-28,
1975.
26. "Automotive News Almanacs Issues for 1974 and 1976,"
published by Marketing Services, Inc.
27. Automotive Exhaust Emissions Manuals for 1972-1975,
published by Michell Manuals, Inc.
R-2
-------
28. "Hearings Before the U.S. Senate on Extension of Auto
Emission Standards," U.S. Congress, November 5-9, 1973.
29. Federal Hearings for Suspension of the 1977 Emission
Standards, January 19, 1975, Environmental Protection
Agency.
30. Requeiro, J.F., "Teledyne Continental Motors Red Seal
Engines First CPCS Application," SAE 750017, February
24-28, 1975.
31. "New Concept in Automotive Ignition," Automotive Engi-
neering, v 84, n3, March, 1975.
32. Bascunna, J.L., "Divided Combustion Chamber Gasoline
Engines - A Review for Emission and Efficiency," APCA
73-74, June 24-28, 1973.
33. Cline, E.L., L. Tinkham, "A Realistic Vehicle Emission
Inspection System, APCA 68-152, June 1968.
34. Sercombe, E.J., "Exhaust Purifiers for Compression
Ignition Engines," Platinum Metal Review, v 19, nl,
January, 1975.
35. Weaver, E.E., et al, "Ford 450 Car Catalyst Field
Test," SAE 741061, October 21-25, 1974.
36. Quander, A.A., "Lean Combustion and the Misfire Limit
in Spark Ignition Engines," SAE 741055, October 21-25,
1974.
37. McWhannel , D.C., "Performance and Emission Characteris-
tics of a Turbocharged Spark Ignition Engine," J.
Automotive Engineering, v 5, n4, August, 1974.
38. "Electro-Pneumatic Fuel Injection Boosts Power, Reduces
Emissions," Automotive Engineering, v 82, n7, July,
1974.
39. Cassidy, J.F., "Electronic Closed Loop Controls for the
Automobile," SAE 740014, February 27-28, 1974.
40. Mullins, P.J., "Low-Cost Fuel Injection," Automotive
Industries, v 151, nl, July, 1974.
41. Ganly, J.T., and G.S. Springer, "Physical and Chemical
Characteristics of Particulates in Spark Ignition
Exhaust," Environmental Science Technology, v 8, n4,
April, 1974.
42. Sweeney, M.P. and M.L. Brubacker, "Exhaust Hydrocarbon
Measurement for Tune-Up Diagnosis," SAE 660105, January
10-14, 1966.
R-3
-------
43. Brubacker, M.L. and D.R. Olson, "Smog Tune-Up for Older
Cars," SAE Paper S403, April 27, 1964.
44. Barnes, G.J., and R.L. Klimisch, "Initial Performance
of Supported NOX Reduction Catalysts in a Dual-Catalyst
System," SAE 740251, February 28 - March 1, 1974.
45. Mitchel, E. and M. Alperstein, "Texaco Controlled and
Combustion System-Multifuel, Efficient, Clean and
Practical," Combustion Science Technology, v 8, nl-2.
46. "Electronic Ijfgnition Uses Optical Trigger," Automotive
Engineering, v 82, n4, April, 1974.
47. Mills, D.L., et al , "Catalytic Emission Control System
Field Test Program," SAE 750179.
48. Bond, W.D., "Quick Heat Intake Manifold for Reducing
Cold Engine Emissions," SAE 720835, October 31 - November
2, 1972.
49. Brubacker, M. and E. Grant, "Do Exhaust Controls Relay
Work?, Second Report," SAE 670689, August 14-15, 1967.
50. Laity, J.L., et al , "Mechanisms of Polynuclear Aromatic
Hydrocarbon Emissions from Automotive Engines," SAE
730835, 'September 10-13, 1973.
51. Anderson, C.J., et al, "Measurement and Evaluation of
Emissions from a Variety of Controlled and Uncontrolled
Light-Duty Vehicles," SAE 730715, August 20-23, 1973.
52. Jaqel, K.I., G.J. Lehman, "Application of Catalytic
Converters for Exhaust Emission Control of Gaseous and
Liquid Fueled Engines," ASTM Spec. Tech. Publication
525, June 25-30, 1972.
53. Chironis, N.P., "Diesels. A Giant Step Underground,"
Coal Age, v 78, n3, March, 1973.
54. Heinen, C., "Using the Engine for Exhaust Control," SAE
S355, January 8-12, 1973, November 19, 1962.
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)
------- |