EPA-340/2-76-002
MARCH 1977
EFFECT OF AUTOMOTIVE
PARTS ON VEHICLE AND
ENGINE EMISSIONS
*
PHASE II - AFTER-MARKET PARTS
U.S. Environmental Protection Agency
Mobile Source Enforcement Division
Technical Support Branch
Washington, D.C. 20460
-------
EPA-3W2-76-002
EFFECT OF AUTOMOTIVE
PARTS ON VEHICLE AND
ENGINE EMISSIONS
PHASE II - AFTER-MARKET PARTS
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
MARCH 1977
-------
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 22161.
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.
i 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 maintenance at the manufacturer's cost, providing
that recommended maintenance and operating procedures had
been followed by the vehicle owner.
Strict interpretation of the Clean Air Act warranty
requirements could, however, lead to voiding of the emissions
warranty if non-OEM components were installed. The EPA, in
the interest of maintaining a viable after-market parts
industry and maximizing consumer choice, elected to sanction
a voluntary program for self-certification of after-market
parts critical to vehicle or engine emissions performance.
Although the major activity under this program would be
performed by the after-market parts industry, the EPA deter-
mined that an independent evaluation of after-market part
criticality was advisable in the interest of advancing the
program.
The objective of this study, therefore, was to
assess the relative importance of after-market engine and
emission control components in causing excessive emissions
111
-------
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
• Probability of defect occurrence
t Duration of defect occurrence
• Relative usage of each component.
IV
-------
ABSTRACT
This final report documents the methodology and
results of Phase II 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 II of the study investigated
the emission-criticality of after-market equipment not
installed or distributed by the original 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
A
using three independent sets of input data. 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
FOREWORD
ABSTRACT
Section
1
1.1
1.2
1.3
1.4
1.5
2
2.1
2.2
2.3
2.4
3
3.1
3.2
3.2.1
3.2.2
3.2.3
3.2.4
3.3
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
3.3.6
3.3.7
3.3.8
3.3.9
3.3.10
3.3.11
3.3.12
3.4
3.4.1
3.4.2
3.4.3
3.4.4
3.4.5
INTRODUCTION AND
Summary of Major
Statement of the
Study Objectives
Study Scope. . .
Study Plan . . .
SUMMARY
Findings
Problem
LITERATURE SEARCH
After-Market Component Usage
Effect of Component Failure on Emissions
Probability and Duration of Component
Failure
Sales Volume of After-Market Components.
EMISSIONS-RELATED COMPONENTS
Criteria and Assumptions
Carburetion System
Assembled Carburetors
Carburetor Control Devices
Carburetor Components
Fuel Filter
Ignition System
Points
Condenser/Capacitor
Distributor
Magnetic or Optical Triggers
Spark Plugs
Ignition Wires
Coils
Capacitive Discharge Systems
Ballast Resistor
Electronic Ignition Circuits
Glow PI ug
Ignition Timing Adjustment
Air Induction System
Thermostatically Controlled Air Inlet.
Air Cleaner Element
Intake Manifolds
Turbochargers
Superchargers
1-1
1-1
1-8
1-9
1-9
1-10
2-1
2-3
2-4
2-22
2-29
3-1
3-1
3-4
3-6
3-9
3-13
3-19
3-19
3-21
3-22
3-22
3-26
3-27
3-27
3-28
3-28
3-29
3-29
3-30
3-30
3-31
3-31
3-34
3-34
3-35
3-35
VI 1
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TABLE OF CONTENTS (Cont'd)
Section
3.5 Fuel Injection System 3-36
3.5.1 Accumulator 3-36
3.5.2 Fuel Pump (High Pressure) 3-37
3.5.3 Fuel Pressure Sensors/Regulators .... 3-37
3.5.4 Throttle Linkage and Valve 3-37
3.5.5 Injection Valves 3-38
3.5.6 Air Sensors/Switches 3-38
3.5.7 Temperature Sensors/Switches 3-39
3.5.8 Fuel Distribution Manifold 3-39
3.5.9 Injectors (Solenoid) 3-39
3.5.10 Triggering Switches 3-40
3.5.11 Electronic Fuel Injection Control
Circuits 3-40
3.5.12 Starting Valve 3-40
3.6 Engine Systems 3-41
3.6.1 Exhaust Valve Components 3-42
3.6.2 Piston Rings 3-44
3.6.3 Pistons 3-45
3.6.4 Gaskets 3-45
3.6.5 Exhaust Manifolds and Headers 3-45
3.7 Emission Control Systems 3-46
3.7.1 Positive Crankcase Ventilation (PCV)
Systems 3-47
3.7.2 Evaporative Emission Control (EVAP)
System 3-49
3.7.3 Air Injection (AI) System 3-52
3.7.4 Exhaust Gas Recirculation (EGR)
Systems 3-55
3.7.5 Transmission-Controlled Spark (TCS). . . 3-59
3.7.6 Orifice Spark Advance Control (OSAC) . . 3-62
3.7.7 Electronic Spark Control (ESC) System. . 3-64
3.7.8 Catalytic Reactor 3-66
3.7.9 Miscellaneous Emissions-Related Parts. . 3-66
3.8 Emissions-Related Parts List 3-70
4 EMISSION-CRITICAL COMPONENTS 4-1
4.1 Criticality Index Model 4-1
4.1.1 Criticality Index 4-5
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 4-43
VI 1 1
-------
TABLE OF CONTENTS (Cont'd)
Section
4.2.3 Probability of Repair Factor 4-51
4.2.4 Component Sales Volume 4-59
4.3 Rankings of Emission-Critical After-
Market Components 4-67
5 CRITICAL PARAMETERS 5-1
5.1 Carburetion System Components 5-2
5.1.1 Carburetors 5-2
5.1.2 Carburetor Components 5-4
5.2 Ignition System Components 5-6
5.2.1 Spark Plugs 5-6
5.2.2 Wires 5-6
5.2.3 Rotors 5-7
5.2.4 Caps 5-7
5.3 Air Induction System Components 5-8
5.4 Mechanical System Components 5-8
5.4.1 Exhaust Manifolds and Headers 5-8
5.4.2 Internal Engine Components 5-9
5.5 Fuel Injection System 5-9
5.6 Emission Control System Components .... 5-9
5.6.1 EGR Valve 5-10
5.6.2 Thermal Vacuum Valve 5-10
5.6.3 EGR Vacuum Amplifier 5-10
5.6.4 Spark Delay Valve 5-10
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 6-4
6.1.3 Air Induction System 6-5
6.1.4 Fuel Injection System 6-5
6.1.5 Mechanical Components 6-6
6.1.6 Emission Control Components 6-6
6.2 Test Protocol 6-7
6.2.1 Vehicle Selection 6-7
6.2.2 Preconditioning 6-8
6.2.3 Test Fuel 6-8
6.2.4 Inspection and Maintenance 6-8
6.2.5 Emission Tests 6-9
REFERENCES R-l
LIST OF APPENDICES
A Criticality Index Rankings A-l
B Criticality Index Input Parameter Values . B-l
IX
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LIST OF ILLUSTRATIONS
Figure
1-1 Study Approach
3-1 Carburetor Vacuum Signals ,
3-2 Effect of Throttle Position on Vacuum
Signals
4-1 Criticality Model Flowchart
Table
LIST OF TABLES
1-1 After-Market Part Criticality Ranking
Garage Sales Volume and Early Model
Emission Factors 1-3
1-2 After-Market Part Criticality Ranking
Warehouse Sales Volume and Early
Model Emission Factors 1-4
1-3 After-Market Part Criticality Ranking
OEM Sales Volume and Late Model
Emission Factors 1-5
1-4 Summary of Critical Parameters of
Emission-Critical After-Market Parts . . 1-6
1-5 After-Market Components Recommended for
Testing 1-7
2-1 Key Words Used for Literature Search . . . 2-2
2-2 Engine Development Literature not
Applicable to Automotive Parts Study . . 2-6
2-3 Effect on Emissions of Various Components. 2-12
2-4 Effect of Idle Parameters on Hot FTP
Emissions 2-15
2-5 Changes in 1975 FTP Emissions Caused By
Specific Defects 2-16
2-6 Effect of Component Defects on 1975 FTP
Emissions 2-18
2-7 Effect of Component Defects on Hot FTP
Emissions 2-19
2-8 Effect of Engine Variables on Steady
State Emissions from Pre-1973 Vehicles . 2-21
2-9 Incidence of Malfunctions 2-24
2-10 Estimated Durability of Automobile Parts . 2-26
2-12 Incidence of Defects in Low Mileage
Catalyst Vehicles 2-27
2-11 Repairs Performed During California
Vehicle Emission Inspection Program. . . 2-28
2-13 Gross Annual After-Market Sales Volume
from Warehouse Distributors Responding
to Survey 2-30
-------
LIST OF TABLES (Cont'd)
Table
2-14 Gross Annual Repair Jobs Performed by
355,000 Repair/Service Shops 2-33
3-1 Emissions-Related Parts List After-
Market Parts 3-71
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 Sales Volume Factors 4-60
4-5 After-Market Part Criticality Ranking
Warehouse Sales Volume and Early Model
Emission Factors 4-68
4-6 After-Market Part Criticality Ranking
Garage Sales Volume and Early Model
Emission Factors 4-69
4-7 After-Market Criticality Ranking OEM
Sales Volume and Late Model Emission
Factors 4-70
4-8 After-Market Components Which Can Cause
an Emission Failure if Improperly
Installed or Defective 4-72
4-9 Automotive Part Criticality Ranking. . . . 4-76
5-1 Summary of Critical Parameters of
Emission-Critical After-Market Parts . . 5-3
6-1 After-Market Components Recommended for
Testing 6-3
XI
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Section 1
INTRODUCTION AND SUMMARY
This report documents the results of Phase II of
the Investigation of the Effect of Automotive Parts on
Vehicle and Engine Emissions, EPA Contract 68-01-1957.
Phase II of this study included all equipment not installed
by or for the original vehicle or engine (OEM) manufacturers.
For purposes of this study, after-market equipment also
excluded replacement components distributed 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 after-
market components and systems. Section 4 discusses the
emission-critical after-market components and the methodology
used to rank them in order of their criticality. Section 5
discusses the critical parameters or specifications of the
most critical after-market components. Section 6 concludes
this report with a recommended test protocol for 25 of the
most critical after-market components.
1.1 SUMMARY OF MAJOR FINDINGS
The major findings of Phase II of this study for
after-market components are the following:
1-1
-------
• Literature clearly defining the effect on FTP
emissions from after-market components
exists for only a few specific components.
• The ranking of emission-critical components
is sensitive to changes in the values of the
input parameters particularly the sales
volume. (See Tables 1-1 through 1-3 for
criticality lists using various values of
input parameters.)
• The most emission-critical after-market
components for HC are typically ignition
tune-up components.
• The most emission-critical after-market
components for CO are carburetors or carburetor
rebuilding components.
• The most emission-critical after-market
components for NO are typically components
y\
which affect vacuum signals controlling
ignition timing and EGR valve operation.
t The most emission-critical after-market
components for smoke are typically mechanical
components of the engine.
Based on the criticality rankings shown in
Tables 1-1 to 1-3, the critical performance parameters for
the 5 components most critical to each pollutant were identi-
fied and are summarized in Table 1-4.
A series of tests were recommended on 25 after-
market components to develop or refine data on emissions
increases and symptoms of failure. These components are
summarized in Table 1-5.
1-2
-------
Table 1-1. AFTER-MARKET PART CRITICALITY RANKING
(Automotive Parts Study - EPA Contract No. 68-01-1957)
GARAGE SALES VOLUME AND EARLY MODEL EMISSION FACTORS
HL
NO"
SMOKE (Diesel)
COMPOSITE
Spark Plugs
Ignition Wires
Cap
Rotor
Rebuilding Kits
Float and Valve
Points
Valve Lifter/Springs
Exhaust Valves
Rebuilt Carburetor
Valve Seals
Condenser
Mag/Opt Triggers
El Control Circuit
New Carburetor
PCV Valve
Piston Rings
Air Cleaner Element
Exhaust Manifold
Fuel Filter
Valve Guides
Specialty Carburetor
Head Gaskets
Valve Cam Lobes
Camshafts
Rebuilding Kits
Float and Valve
Air Cleaner Element
PCV Valve
Valve Lifter/Spring
Rebuilt Carburetor
Exhaust Valves
Valve Seals
New Carburetor
Piston Rings
Exhaust Manifold
Valve Guides
Specialty Carburetor
Head Gasket
Valve Cam Lobes
Camshafts
High Perf Exhaust
FI Hi Pres Pump
Idle Stop Solenoid
Throttle Dashpot
Throttle Positioner
Metering Jets
Metering Rods
Vacuum Break Valve
Choke Mechanism
Exhaust Manifold
Rebuilt Carburetor
Specialty Carburetor
New Carburetor
High Perf Exhaust
Valve Lifter/Spring
Exhaust Valves
Air Cleaner Element
Valve Seals
Piston Rings
Valve Guides
Head Gaskets
Valve Cam Lobes
Camshafts
FI Hi Pres Pump
Spark Plugs
Ignition Wires
Rebuilding Kits
Float and Valve
Cap
Rotor
Air Cleaner Element
PCV Valve
Points
Valve Lifter/Springs
Rebuilt Carburetor
Exhaust Valves
Valve Seals
New Carburetor
Condenser
Mag/Opt Triggers
El Control Circuit
Piston Rings
Exhaust Manifold
Fuel Filter
Valve Guides
Specialty Carburetor
Head Gaskets
Valve Cam Lobes
Camshafts
-------
Table 1-2. AFTER-MARKET PART CRITICALITY RANKING
(Automotive Parts Study - EPA Contract 68-01-1957)
WAREHOUSE SALES VOLUME AMD EARLY MODEL EMISSION FACTORS
HC
TTT
T
SMOKE (Diesel)
COMPOSITE
Spark Plugs
Ignition Wires
Rebuilding Kits
Rebuilt Carburetor
Rotor
Cap
Choke Mechanism
New Carburetor
Valve Lifter/Spring
Points
Valve Seals
Exhaust Valves
Specialty Carburetor
Coil
Condenser
PCV Valve
Air Cleaner Element
Spark Delay Valve
Fuel Filter
Distributor Drive
EVAP Fresh Air
AI Hoses
Valve Guides
Head Gaskets
Piston Rings
Rebuilding Kits
Choke Mechanism
Rebuilt Carburetor
New Carburetor
Air Cleaner Element
Valve Lifter/Spring
PCV Valve
Valve Seals
Exhaust Valves
Specialty Carburetor
Vacuum Break Valve
PCV Freshair Filter
Idle Stop Solenoid
Throttle Dashpot
Decel Valve
AI Hoses
Valve Guides
Head Gaskets
Piston Rings
Camshafts
Vacuum Advance
AI Pump/Belts
Intake Manifold
Mechanical Advance
Valve Cam Lobes
Thermal Vac Valve
Spark Delay Valve
EGR Valves
Rebuilt Carburetor
Specialty Carburetor
New Carburetor
EGR Vacuum Amplifier
TCS Vacuum Solenoid
TCS Temp Switch
Mechanical Advance
Exhaust Manifold
High Perf Exhaust
Valve Lifter/Spring
Valve Seals
Exhaust Valves
Air Cleaner Element
FI Throttle Valve
Valve Guides
Head Gaskets
Piston Rings
Camshafts
Valve Cam Lobes
FI Hi Pres Pump
Spark Plugs
Rebuilding Kits
Ignition Wires
Choke Mechanism
Rebuilt Carburetor
New Carburetor
Rotor
Cap
Air Cleaner Element
Valve Lifter/Springs
Thermal Vacuum Valve
PCV Valve
Spark Delay Valve
Points
EGR Valves
Valve Seals
Exhaust Valves
Specialty Carburetor
Vacuum Break Valves
PCV Fresh Air Filter
Coil
Idle Stop Solenoid
Condenser
EGR Vacuum Amplifier
Throttle Dashpot
-------
Table 1-3. AFTER-MARKET PART CRITICALITY RANKING
(Automotive Parts Study - EPA Contract 63-01-1957)
OEM SALES VOLUME AND LATE MODEL EMISSION FACTORS
"HT
SMOKE (Diesel)
COMPOSITE
Spark Plugs
Ignition Wires
Rebuilding Kits
Float and Valve
Choke Mechanism
Power Valves
EVAP Canister
Rebuilt Carburetor
Heat Riser
PCV Valve
Rotor
Cap
-------
Table 1-4. SUMMARY OF CRITICAL PARAMETERS OF EMISSION-CRITICAL AFTER-MARKET PARTS
SYSTEM/COMPONENT
Carburetion System
Rebuilding Kits
Rebuilt Carburetors
New Carburetors
Specialty Carburetors
Choke Thermostats
Float and Valves
Power Valves
Ignition System
Spark Plugs
Ui res
Rotors
Caps
Induction System
Air Cleaner Elements
Mechanical System
Exhaust Manifolds
Headers
Valve Lifters/Springs
Exhaust Valves
Valve Seals
Piston Rings
Fuel Injection System
MFI Valves
FI Throttle Valves
Emission Control System
EGR Valves
Thermal Vacuum Valves
EGR Vacuum Amplifiers
Spark Delay Valves
CRITICAL PARAMETERS
Dimensions
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Materials
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Flow Curve
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Movement
X
X
X
X
X
X
X
X
X
X
Electrical
X
X
X
X
Thermodynamic
X
X
X
X
X
X
X
X
X
X
-------
Table 1-5. AFTER-MARKET COMPONENTS RECOMMENDED FOR TESTING
COMPONENT
Carburetion System
New Carburetor
Rebuilt Carburetor
Specialty Carburetor
Carburetor Rebuilding Kit
Choke Thermostat
Float and Valve
Metering Jet
Dashpot
Ignition System
Spark Plugs
Ignition Wires
Points
Condenser
Coil
Distributor Cap
Distributor Rotor
Vacuum Advance Unit
Retrofit CD Electronic Ignition
Optical/Magnetic Retrofit
El Distributor System
Replacement Distributor
Engine System
Valve Lifters/Springs
Intake Manifold/Headers
Emission Control System
PCV Valve
Decel Valve
Spark Delay Valve
Thermal Vacuum Valve
TES
OEM -
OEM -
OEM -
OEM -
OEM -
OEM -
Lean -
OEM -
OEM -
OEM -
OEM -
OEM -
OEM -
OEM -
OEM -
OEM -
OEM -
OEM -
OEM -
OEM -
OEM -
OEM -
OEM -
OEM -
OEM -
T CONDITIONS
After-market
After-market
After-market
Rebuilding Kit
After-market
After-market
OEM - Rich
After-market
After-market
After-market
After-market
After-market
After-market
After-market
After-market
After-market
After-market
After-market
After-market
After-market
After-market
After-market
After-market
After-market
After-market
1-7
-------
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
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
emission standards during the 50,000-mile warranty period
are subject to recall and corrective repair at the manufac-
turer'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 maintenance
schedules covering those adjustments and component replace-
ments which the manufacturers have found to be important in
maintaining compliance with the emission standards for
50,000 miles.
Strict interpretation of the Clean Air Act warranty
requirements could, however, lead to voiding of the emissions
warranty if non-OEM components were installed. The EPA, in
the interest of maintaining a viable after-market parts
industry and maximizing consumer choice, elected to sanction
a voluntary program for self-certification of after-market
parts critical to vehicle or engine emissions performance.
Although the major activity under this program would be
performed by the after-market parts industry, the EPA deter-
mined that an independent evaluation of after-market part
criticality was advisable in the interest of advancing the
program.
1-8
-------
1.3 STUDY OBJECTIVES
The objective of this phase of the study was to
assess the relative importance of after-market parts in
causing excessive emissions in the in-service vehicle popula-
tion. 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
• Probability and duration of defect occurrence
• Relative usage of each component.
Additional objectives included determining critical
performance parameters for the most critical after-market
components, and recommending test protocols for 25 of the
most critical after-market components.
1.4 STUDY SCOPE
This study was conducted in two phases. Phase I
consisted of an assessment of the criticality of original
factory installed (OEM) equipment. Phase II consisted of an
assessment of the criticality of after-market equipment
including both high performance equipment and OEM equivalent
replacement components. This study was accomplished without
testing but was supported by a literature search and engineer-
ing 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 (percent opacity). All engines
A
subject to regulation were within the nominal scope of the
study; however, as a practical matter, diesel engine and
1-9
-------
heavy duty gasoline engine components were not included in
the criticality ranking of HC, CO, and NO because of the
A
relatively low occurrence of these engines in the population
The emission-criticality of after-market components for
smoke was 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 having similar
function and configuration. Each class or category of
components was then assigned parameter values which were
applied to all individual components within each category.
1.5 STUDY PLAN
Figure 1-1 illustrates the sequence and interrela-
tionship of the tasks of both phases of the 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 which were documented in the Final Report for Phase I
(Ref. 107):
• Identify emissions-related systems and
components.
• 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
the end of component design life.
1-10
-------
PREPARE
PLAN OF
PERFORMANCE
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
RECOMMEND
OEM
PARTS
TESTING
PREPARE
PHASE I
REPORT
DEFINE
CRITICAL
PARAMETERS
FOR AFTER-
MARKET PARTS
RECOMMEND
AFTER-MARKET
PARTS
TESTING
PREPARE
PHASE II
REPORT
Figure 1-1. STUDY APPROACH
-------
• Determine relative usage (sales volume) of
each OEM component.
0 Use the factors defined above to calculate a
criticality index for each OEM component for
each pollutant.
t 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
1iterature.
Phase II activity included the following tasks
relative to after-market components, parts, and systems:
• Redefine the values of the criticality index
input parameters for after-market components.
t 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 above analyses and subsequent findings, conclu-
sions, and recommendations formed the basis of this Final
Report on Phase II of the Investigation of the Effect on
Automotive Parts on Vehicle and Engine Emissions.
1-12
-------
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.
• 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
words shown in Table 2-1. Unfortunately, the search was
2-1
-------
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) Maintainabi1ity
Catalyst(s) Mileage
Component(s) Mobile Source(s)
Diesel NitricOxide
Durability Oxide(s) of Nitrogen
Electrical Parts
Emission(s) Reactor
Engine(s) Smoke
Exhaust Sparklgnition
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:
2-2
-------
• Component usage.
• Effect of component failure on emissions.
• Probability and duration of component failure.
• Sales volume.
2.1 AFTER-MARKET COMPONENT USAGE
In order to identify emissions-related after-
market components, it was necessary to determine which
components and systems were available through after-market
sources. For purposes of this study, after-market components
were defined to include all components not built by or for
the vehicle or engine manufacturers. This definition excluded
replacement components distributed by the vehicle or engine
manufacturers through their authorized service centers and
parts divisions. In general, the after-market component
sources corisidered in this study included the following:
• Nationally advertised name brand components
sold as OEM component replacements (plugs,
wires, points, condensers, air filters, PCV
valves , etc.).
• Private brand components distributed by major
retail chains and sold as OEM component
replacements (same components as above).
• Rebuilders selling components rebuilt and
restored to OEM specifications (primarily
carburetors, air injection pumps, and mechan-
ical components such as heads, engine blocks,
crankshafts, pistons, valves and valve train
components).
2-3
-------
t Add-on specialty components not intended to
be OEM replacements. Add-on components fall
into the following four major system categories
ignition, air induction, carburetion, and
exhaust system.
After-market parts can be generally characterized
as replacement or specialty components. Most after-market
parts are sold as OEM replacement parts with only 1 percent
to 3 percent of sales volume for most categories attributable
to specialty components (Ref. 105). Furthermore, most
after-market parts, whether replacement or specialty, are
sold for vehicles which are at least 2 to 3 years old. This
is because of the longer maintenance intervals on newer
vehicles, the higher frequency of component failure on older
vehicles, and the common consumer practice of returning to
the dealer for repairs or service during the major mechanical
engine warranty period.
In general, nearly all standard ignition, carbure-
tion, and mechanical components used on vehicles are available
through the after-market. Certain special purpose and/or
low production volume components, however, are available
only through the original engine or vehicle manufacturer's
parts and service centers. These components, therefore, are
not readily available to the after-market. In general, as a
vehicle becomes older, after-market sources of supply gradu-
ally become available to satisfy demand from independent
jobbers and garages who perform the majority of repairs on
older vehicles.
2.2 EFFECT OF COMPONENT FAILURE ON EMISSIONS
The literature search was mainly conducted during
Phase I, the original equipment portion of the study. Very
2-4
-------
little technical literature explicitly concerned after-
market parts. For replacement components, this was not a
serious problem since they are nominally identical in design
and performance characteristics to the OEM components which
they replace. They would be expected to have similar failure
modes and affects on emissions as the corresponding OEM
component. The literature on OEM components, therefore, is
applicable to these after-market components and provides the
best available information.
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 component
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.
2-5
-------
Table 2-2. ENGINE DEVELOPMENT LITERATURE NOT APPLICABLE
TO AUTOMOTIVE PARTS STUDY
REFERENCE
NO.
TITLE
SOURCE
1
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
Conditions.
SAE 740105
SAE 730227
SAE 751181
SAE 750351
SAE 740123
SAE 740252
SAE 740188
SAE 750787
SAE SP-395
Iirst. of Gas
Techno! , Chicago
6/5-7/72
-------
Table 2-2. ENGINE DEVELOPMENT LITERATURE NOT APPLICABLE
TO AUTOMOTIVE PARTS STUDY (Continued)
REFERENCE
NO.
25
30
31
32
34
36
39
41
44
45
50
TITLE
Closed Loop Carburetor Emission Control System
Teledyne Continental Motors Red Seal Engines First CPCS
Appl ication .
New Concept in Automotive Ignition.
Divided Combustion Chamber Gasoline Engines - A
Review for Emission and Efficiency.
Exhaust Purifiers for Compression Ignition Engines.
Lean Combustion and the Misfire Limit in Spark Ignition
Engines .
Electronic Closed Loop Controls for the Automobile.
Physical and Chemical Characteristics of Particulates
in Spark Ignition Engine Exhaust.
Initial Performance of Supported NO Reduction
Catalysts in a Dual -Catalyst System.
Texaco Controlled Combustion System Multifile! , Efficient,
Clean and Practical
Mechanisms of Polynuclear Aromatic Hydrocarbon Emissions
from Automotive Engines.
SOURCE
SAE 750371
SAE 750017
Automot . Eng . ,v
84, n3, 3/75
APCA 73-74
6/24-28/73
Platinum Met Rev,
v 19 nl, 1/75
SAE 741055
SAE 740014
Environ. Sci.
Technol , v 8 ,
n4, 4/75
SAE 740251
Combust. Sci .
Technol , v 8 , n
SAE 730835
-------
Table 2-2. ENGINE DEVELOPMENT LITERATURE NOT APPLICABLE
TO AUTOMOTIVE PARTS STUDY (Continued)
REFERENCE
NO.
TITLE
SOURCE
IN5
I
CO
55
61
62
77
76
88
Simulated Road Test Evaluation of the Effect of Gasoline
Additives on Exhaust Gas Emissions.
Control of Exhaust Pollution through a Mixture Optimizer.
Closed Loop Control of Internal Combustion Engine Exhaust
Emissions.
Emissions Control Technology of Heavy Duty Vehicle
Engines .
Experiments with a Catalytic Cleaner for Car Engine
Exhaust Gases .
An Evaluation of the Emissions Characteristics of the
Exxon Well Mixed Thermal Reactor.
SAE 720942
SAE 720254
PB-239 850/1ST
DOT-OS-30 111
2/74
PB-236 899/1ST
EPA-68-01-0472
12/73
N75-12455/2ST
FOA-1-C-1492-H3
12/72
PB-220 034/3
APTD-1387, 72-3
-------
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
emissions and increased NO emissions. Unfortunately, the
A
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 emission 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
2-9
-------
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 attributed partly to plug fouling. Ignition misfire
was believed to have caused the catalyst failures. However,
converter failures occurred when at least two cylinders were
misfiring. More rapid deterioration of HC than CO emissions
generally occurred, with NO emissions showing little
J\
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 collapse).
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.
t Failure of coasting protection (deceleration
controls).
• Misfire caused by ignition failure.
• Complete ignition failure at moderate to high
speed.
t 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
2-10
-------
destroyed. If the catalyst was 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 and 18.0 gm/mi CO.
A summary NAS report (Ref. 70) presented a compila-
tion of emission-critical components which has been abstracted
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 tempera-
ture. 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 probability of
repair factor. The criticality ranking of the components
was as follows:
t Two cylinders misfiring.
• One cylinder continuously misfiring.
• One cylinder intermittently misfiring.
t One cylinder occasionally misfiring.
t Choke valve stuck.
§ Fuel restriction (lean operation).
0 Plugged air bleed.
t Main jet fell out.
0 Carburetor flooding.
• Primary jet fell out.
A study (Ref. 17) for the California Air Resources
Board (CARB) investigated the sensitivity of FTP emissions
2-11
-------
Table 2-3. EFFECT ON EMISSIONS OF VARIOUS COMPONENTS
1
NO. ITEM
Major Control Equipment
1* 3-way catalyst (HC, CO, NOX)
2* Reduction catalyst (NO )
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
N0x
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.
2-12
-------
Table 2-3. EFFECT ON EMISSIONS OF VARIOUS COMPONENTS (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
N0x
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.
2-13
-------
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
N0x
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
SERVICt
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.
2-14
-------
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
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
PRL-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
/\
systems and advanced basic timing.
2-15
-------
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
NOX
65
41
0
35
-12
-
-12
-
-
0
DIAGNOSED DEFECTSb
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).
2-16
-------
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:
• Restricted air cleaner or timing variations
of ±10° did not significantly affect FTP
emissions.
t Disconnected air injection caused significant
increases in HC and CO emissions but reduced
NO emissions.
A
0 A stuck choke increased HC and CO emissions
on large engines but not necessarily on small
engines. NO emissions were reduced, signifi-
A
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
A
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).
A
These data indicated that intentional maladjustment or
2-17
-------
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
NO
A
1.46
1.41
1.81
1.23
5.60
1.24
0.35
2.55
ro
i
i—1
oo
-------
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
controlled experiment included timing, idle speed, idle
mixture, air cleaner restriction, PCV restriction, and NOV
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.
/\
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)
h 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
NOX
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 emis-
sion test program performed by Exxon. The first paper
included a survey of 23 previous papers relating component
2-19
-------
defects to qualitative steady-state emissions (Table 2-8).
No quantitative data based on FTP emissions were presented.
However, substantial 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.
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.
Data on the source of parts used in repairing vehicles which
failed the emission inspection was not reported in these
references. However, use of after-market parts is common
practice by the independent service industry which performs
many of the repairs required in these studies. Therefore,
since reasonable emission reductions were achieved in most
of these studies, they imply that after-market replacement
components do not adversely affect emissions.
An EPA study (Ref. 104) evaluated the effect of
high performance centrifugal advance springs which provided
more advance at low and moderate engine speed than OEM
springs. The special springs were found to increase emis-
sions of all three pollutants without substantially improv-
ing fuel economy. These tests were run on a 1974 Chevrolet
with 350-CID engine.
A report by the Specialty Equipment Manufacturers
Association (Ref. 105) showed that off-the-shelf performance
components could either improve or degrade emissions relative
to the OEM components, depending on the OEM system configura-
tion and calibration, and the amount of optimizing adjustments
performed. However, the average emission reduction measured
2-20
-------
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
-
2-21
-------
by the 1975 FTP was approximately 25 percent for HC, 30 per-
cent for CO and 40 percent for NO from four typical 1969
A
model-year vehicles. Data on more recent vehicles is cur-
rently being developed.
The California Air Resources Board (Ref. 106)
conducted a preliminary test program to investigate the
effect of certain after-market components on emissions. In
general, ignition components did not affect emissions
unless ignition timing was modified. Carburetion intake
manifold or exhaust system modifications could either increase
or decrease emissions depending on the component, base
engine, and degree of optimizing adjustments performed.
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
reduced 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 strong relationship between performance
2-22
-------
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.
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). None of the studies suggested that after-
market components had higher failure rates than the equivalent
OEM component. However, errors in component installation or
adjustment by service personnel may result in excessive
emissions. This has been reported for rebuilt carburetors
(Ref. 33).
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.
2-23
-------
Table 2-9. INCIDENCE OF MALFUNCTIONS
(ABSTRACTED FROM TABLES 7 AND 8 OF REF. 12)
DESCRIPTION
Igni tion
Mixture
Engine RPM
Carburetor
Choke
Timing
PCV Valve
Air Fi 1 ter
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
-
2-24
-------
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
1 i f e .
A consultant report to the NAS (Ref. 73) described
some probable maintainability and reliability data for 1975-
1976 configuration vehicles:
f EGR maintenance should be reduced by lead-
free fuel because particulate (deposits)
emissions are reduced.
t Spark plug life should be increased by lead-
free fuel and high energy ignition systems.
• 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.
a Vacuum line, vacuum motor, vacuum diaphragm,
and exhaust pressure diaphragm malfunction
should be low (fraction of 1 percent in the
vehicle population).
2-25
-------
Table 2-10. ESTIMATED DURABILITY OF AUTOMOTIVE 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 1 ine
Air cleaner - plugged
Ignition
Misfire--plugs
Misf ire--wiring
Misfire--cap and rotor
Basic timing
Automatic spark advance
Devices
PCV system
EGR system
Air pump system
Oxidation catalyst
Reduction catalyst
Evaporative control system
Other
Idle speed
Burned exhaust valve
Low compression
MEAN TIME-TO
FAILURE (MI)
Scott
Labs.
15,000
30,000
—
25,000
25,000
--
50,000
35,000
20,000
20,000
25,000
30,000
15,000
25,000
30,000
--
40,000
25,000
25,000
70,000
15,000
90,000
60,000
American
Motors
25,000
--
--
25,000
5,000
--
50,000
50,000
15,000
15-30,000
50,000
50,000
15,000
100,000
15,000
12-50,000
100,000
12,000
—
50,000
15,000
100,000
100,000
SERVICE
INTERVAL (MI)
Chrysler
12,000
12,000
12,000
6 months
6 months
--
--
Infrequent
12,000
18,000
Infrequent
Infrequent
12,000
12,000
12,000
12,000
12,000
_ _
12,000
12,000
Infrequent
Infrequent
2-26
-------
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 adjust-
ments and off idle carburetion problems.
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
Mixture
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
2-27
-------
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 Misc. Repairs
(Mechanical, Ignition,
Vacuum)
100
2
3
16
4
13
12
12
10
4
5
1
82
2
3
8
1
3
3
2
2
1
3
1
2-28
-------
2.4 SALES VOLUME OF AFTER-MARKET COMPONENTS
Data on the sales volume of after-market components
was not compiled in a form suitable for this study. The
data available was applicable only to certain component
categories and did not distinguish between model-years. A
major limitation of the available data was the fact that
many component manufacturers distributed parts to both OEM
and after-market customers. In these cases, it was impossible
to determine the faction of sales attributable to the after-
market .
A further limitation in the data involved the
changing component mix in the after-market. After-market
sales lag behind OEM sales by several years. Therefore,
emission control system parts which are now exclusively OEM-
distributed may become readily available in the after-
market within several years. This has already occurred with
PCV valves and air injection components which have been
standardized and installed on vehicles for many years.
In an effort to estimate sales of after-market
parts, two approaches were employed. First, the actual
sales level of components was solicited from several sources.
Members of the Automotive Warehouse Distributors Association
(AWDA) were surveyed to acertain their sales volume of
emissions-related parts. Unfortunately, only a few responses
were received with the majority of the respondents indicating
that the requested data was not accessible without explicitly
identifying all the desired components by part number.
Several respondents did, however, provide estimates of their
sales volumes. The gross annual sales volume for those AWDA
members responding is summarized in Table 2-13.
In addition to AWDA, the Automotive Liaison Council
(ALC) was approached for information on sales volume.
However, the ALC itself had not been able to quantify compo-
nent sales volumes of its own members.
2-29
-------
Table 2-13. GROSS ANNUAL AFTER-MARKET
SALES VOLUME FROM WAREHOUSE DISTRIBUTORS
RESPONDING TO SURVEY
CARBURETION SYSTEM COMPONENTS
New Carburetors 83,164
Rebuilt Carburetors 80,112
Carburetor Rebuilding Kits 82,236
Vacuum Breaks 17,844
Choke Components (Thermostats) 43,514
Throttle Dashpots 8,567
Idle Stop Solenoids 16,600
Decel Valves 3,024
Air Filters 189,956
IGNITION SYSTEM COMPONENTS
Spark Plugs 3,903,000
Wires 138,668
Caps 93,636
Rotors 109,916
Replacement Distributors 12,800
Mechanical Advance Units 2,400
Vacuum Advance Units 10,260
Condensers 179,332
Coils 28,980
CD Electronic Ignition Systems 1,440
Electronic Ignition Distributor Kits 408
Electronic Ignition Replacement Components 3,600
FUEL INJECTION COMPONENTS
Fuel Pumps 112,100
Throttle Valves 2,400
ENGINE COMPONENTS
Intake/Exhaust Valves 62,544
Valve Lifters 85,467
Springs 31,630
Piston Rings 61,312
Intake Manifolds 888
Exhaust Manifolds 600
Headers 396
Heat Riser Components 6,446
Pistons 17,468
Head Gaskets 61,920
Exhaust Pipes/Systems 812,136
Cams 3,404
Camshafts 61,312
2-30
-------
Table 2-13. GROSS ANNUAL AFTER-MARKET
SALES VOLUME FROM WAREHOUSE DISTRIBUTORS
RESPONDING TO SURVEY (Cont'd)
EMISSION CONTROL COMPONENTS
Evaporative Emission Filters 18,460
PCV Valves 109,660
PCV Breather Filters 43,344
Air Cleaner Thermostats 6,800
Ram Air Ducts 600
Air Cleaner Preheater Ducts 16,000
Air Cleaner Vacuum Motors 10,000
Vacuum Hoses 8,476
EGR Valves 5,800
EGR Vacuum Amplifiers 3,000
Thermal Vacuum Valves 20,000
Temperature Switches 5,300
Vacuum Solenoid Valves 5,620
Air Injection Pumps 716
Air Injection Hoses 8,750
Air Injection Diverter/Bypass Valves 2,636
In-line Delay Valves (Spark Delay) 20,200
2-31
-------
Table 2-14 summarizes repairs performed in commer-
cial garages, service stations, and dealerships (Ref. 106)
on certain engine, ignition, and carburetion components
during 1975. Except for filters and PCV valves, however, no
emission control components were included.
The second approach consisted of using estimated
component usage developed during the Phase I portion of the
study on original equipment (Ref. 107). These estimates
were based on determining how many of each component was
used and how many replacements were recommended during the
emission warranty period by engine family. The above
information was obtained from the Emission Control Service
Manuals (Ref. 27) published by Mitchell Manuals, Inc., San
Diego, California, and from the recommended maintenance
instructions provided by the vehicle manufacturers. The
total component sales estimates were then generated by
multiplying the component usage of each engine family by
its estimated sales volume (Ref. 26 and 103). These sales
volume factors are shown in Paragraph 4.2.4. Their develop-
ment is discussed more fully in the Phase I final report
(Ref. 107).
2-32
-------
Table 2-14. GROSS ANNUAL REPAIR JOBS PERFORMED
BY 355,000 REPAIR/SERVICE SHOPSl
(JOBS IN THOUSANDS)
TARBURETION WORK
Carburetors Installed (New) 1,515
Carburetors Installed (Rebuilt) 2,567
Carburetors Cleaned on Vehicles 7,336
Carburetors Overhauled (In Shop) 8,271
Fuel Pumps Installed (New) 5,224
Fuel Pumps Installed (Rebuilt) 1,914
Fuel Filters Replaced 36,313
Air Filters Replaced (Engine Overhaul) 6,183
Air Filters Repl. (Non-Eng. Overhaul) 46,926
IGNITION WORK
Engine Tune-Ups (Car) 57,021
Engine Tune-Ups (Truck/Bus) 9,452
Retiming Jobs 17,252
PCV Valves Cleaned or Replaced 35,778
Ignition Breaker Points Installed 61,200
Ignition Wiring Installed (Sets) 10,216
Ignition Wiring Installed (Wires) 10,876
Spark Plugs (New) 390,835
Spark Plugs (Cleaned/Regapped/Reinstal1ed) 23,646
Electronic Ignition Installed (Retrofit) 1,069
Electronic Ignition Control Units Replaced 1,295
Reluctors or Trigger Wheels Replaced 1,779
Pick-up Unit or Pole Piece Replaced 725
Voltage Regulators Installed (New) 8,970
Voltage Regulators Installed (Reblt) 1,437
Voltage Regulators Adjusted 2,777
Abstracted from Ref. 106, "1975 Service Job Analysis
Hunter Publishing Co., Chicago - 1976, pages 10-15.
2-33
-------
Table 2-14. GROSS ANNUAL REPAIR JOBS PERFORMED
BY 355,000 REPAIR/SERVICE SHOPS1
(JOBS IN THOUSANDS - Continued)
ENGINE WORK
Valve Grinding Jobs (Car)
Valve Grinding Jobs (Truck/Bus)
Cylinder Blocks Recond'ed (Blocks)
Cylinder Blocks Recond'ed (Cyl's)
Crankshafts Reconditioned
Piston Rings Inst. (8 Cyl . Cars-Sets)
Piston Rings Inst. (6 Cyl. Cars-Sets)
Piston Rings Inst. (4 Cyl. Cars-Sets)
Piston Rings Inst. (8 Cyl. Trk/Bus-Sets )
Piston Rings Inst. (6 Cyl. Trk/Bus-Sets)
Piston Rings Inst. (4 Cyl. Trk/Bus-Sets)
Rod Bearings Installed (Sets)
Main Bearings Installed (Sets)
Valves Replaced
Hydraulic Valve Lifters Installed
Timing Gears Installed
Camshafts Installed (New)
Camshafts Installed (Reground)
Timing Chains Installed (New)
5,653
1,464
1,150
7,864
1,016
1,909
690
821
902
549
130
3,376
2,838
13,248
17,419
3,426
775
873
3,217
2-34
-------
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 II report
consist of those available through the after-market for 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, "after-market"
included all automotive systems, parts, and components which
were not built by or for the vehicle or engine manufac-
turers. These components are not necessarily in compliance
with regulations issued under Title II of the Clean Air Act.
Under this contract, after-market equipment did not include
3-1
-------
those replacement parts which were identical to factory
installed components if they were built by or for the
vehicle or engine manufacturer. This definition was inter-
preted so that all replacement parts or components distributed
by the original vehicle/engine manufacturers through their
dealer or authorized service center networks were excluded
from the analysis of after-market part criticality, even
though these components are generally considered after-
market parts by the industry.
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 defects in all of
the components would always cause an emissions failure. It
was also impossible to determine whether a nominally function-
ing after-market component used in an improper application
would necessarily cause an emission 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.
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
3-2
-------
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
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 compo-
nents 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
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:
t Carburetion system
t Ignition system
3-3
-------
• Air induction system
• Fuel injection system
• Miscellaneous engine systems
• Emission control systems
The literature surveyed in Section 2 and an engi
neering evaluation formed the basis 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:
t Complete carburetor assemblies, either new
replacement or rebuilt.
• Carburetor control devices external to the
carburetor itself which modify the carburetor
performance under special operating conditions,
t Individual carburetor components including
carburetor rebuilding kits.
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
3-4
-------
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
i ncreases.
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.
• Ruptured power valve (economiser) vacuum
diaphragm.
• Worn or improperly set metering rods.
• Improperly set or defective float and needle
valve.
• Improper idle adjustment.
t Improper jet size.
• 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.
t Ruptured accelerator pump vacuum diaphragm
(if equipped).
t Worn or broken gaskets.
• Ruptured vacuum diaphragms.
• Improper idle adjustment.
t Improperly set float level.
3-5
-------
• 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
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
X
result in increased NO due to higher combustion 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.
A
3.2.1 Assembled Carburetors
Complete carburetors, either new or rebuilt, are
sold ready for installation on the vehicle. All necessary
interface and accessory components, including 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 after-
market replacement carburetors, factory rebuilt carburetors,
3-6
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or carburetors repaired by mechanics. Therefore, separate
part categories have been defined for new after-market and
rebuilt after-market carburetors. In many cases, after-
market carburetors are dimensionally equivalent to OEM
carburetors but have different flow calibrations. Replace-
ment carburetors can also be used on different engines than
for which they were originally sold. They can, therefore,
have high emissions even though no overt defects are present.
Carburetor performance can affect all three pol-
lutants, although CO is usually the most sensitive to defects
or improper adjustment. Gross carburetor malfunction is
usually associated with one or more of the following compo-
nents (Ref. 2, 3, 16, 78, and 27):
• Choke
• Power valve
t Metering jets and rods
• Float adjustment
• Accelerator pump
t Idle adjustment
• 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 or adjustable, they
have been treated individually in this study.
In addition to fuel metering and mixing, carburetors
can also affect the strength and characteristics of vacuum
signals used to control ignition timing advance and EGR
valve operation, and to operate other emissions, performance,
or comfort-related accessories. Replacement carburetors
which do not provide equivalent vacuum signals as a function
of engine speed and load can affect both emissions and
performance.
3-7
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There are three sources of vacuum, each of which
behave differently for any given engine operating condition.
These three vacuum signals have been named venturi vacuum,
ported vacuum, and intake manifold vacuum corresponding to
the location of the source in the carburetor.
Figure 3-1 illustrates the general location of
these sources in a typical carburetor.
VENTURI
1VACUUM
PORTED
VACUUM
HNTAKE ,
£J MANIFOLD
VACUUM
Figure 3-1. CARBURETOR VACUUM SIGNALS
The venturi vacuum tap is located in the carburetor venturi.
The amount of vacuum present at this venturi tap depends on
the velocity of air flowing through the carburetor which, in
turn, depends on engine speed and throttle opening. There-
fore, a stronger vacuum is available at high speed and load
than at low speed and/or load. Venturi vacuum, which
typically ranges between 0 to 5 inches of mercury, is fre-
quently used to control EGR valve operation in those applica-
tions where EGR is proportional to high load and/or speed.
The intake manifold vacuum tap is located somewhere
below the throttle plate. This tap can be in the carburetor
3-8
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itself or in the intake manifold. This source of vacuum is
at a maximum when the throttle plate is closed and at a
minimum when the throttle plate is wide open. This vacuum
typically varies from 17 to 22 inches of mercury at idle to
about 0 inches of mercury at wide open throttle. Manifold
vacuum is usually used for vacuum-operated accessories and
may include a vacuum reservoir to ensure that vacuum is
present during all operating conditions. Manifold vacuum is
frequently used to modulate ignition timing and to provide
PCV and evaporative canister purging.
The ported vacuum tap is usually located just
above the throttle plate. For this reason, when the engine
is idling and the throttle plate is closed, there is no
vacuum signal at the ported vacuum tap. When the throttle
is opened, the ported vacuum tap will be exposed and will
sense the vacuum below the throttle plate. This vacuum will
be essentially the same as manifold vacuum and will behave
much the same as manifold vacuum except during closed throttle
operation. This ported vacuum typically varies from 0 to
about 14 inches of mercury, depending on throttle opening
and the port configuration. Ported vacuum is often used
to control emission control systems and ignition timing.
Figure 3-2 shows the relationship between vacuum
signals at different ports for different throttle plate
positions.
3.2.2 Carburetor Control Devices
t\
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
3-9
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a) IDLE
(P)
(M)
b) OFF IDLE
c) WIDE OPEN THROTTLE
Figure 3-2. EFFECT OF THROTTLE POSITION ON VACUUM SIGNALS
3-10
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carburetor defects. These components are generally available
from after-market distributors although they are manufactured
by OEM vendors.
3.2.2.1 Idle-Stop Solenoid
The idle-stop solenoid is used on most 1972 and
later model-year vehicles to provide a predetermined throttle
setting. The solenoid becomes energized when the ignition
key is turned on. When energized, the plunger extends and
contacts the carburetor throttle 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).
Failures of the idle-stop solenoid would involve
misadjustment or 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. Exces-
sive 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.
3-11
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3.2.2.2 Throttle Dashpot
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 the
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.
3.2.2.3 Throttle Positioners
Throttle positioners are used to hold the throttle
slightly open during deceleration to provide a more combus-
tible 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.
3-12
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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. These components are
generally sold in kit form (see paragraph 3.2.3.8), but may
be purchased individually. Normal shop practice is to
replace all major carburetor components when a carburetor is
rebui1t.
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). More impor-
tantly for the after-market, however, larger carburetor jets
can be installed in most carburetors to improve driveability
and performance. 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
3-13
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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 basic choke position is
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. The vacuum break valve opens the choke slightly to
lean out mixture as soon as the engine starts.
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
3-14
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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
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 or disconnected 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 in the after-
market will be incorrect adjustment or loose pump piston
seal. Both situations will enrichen the mixture and increase
CO and HC mass emissions (Ref. 2, 3 and 27).
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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).
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.
3-16
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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 OEM vehicle manufactur-
ers .
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 emissions (Ref.
16, 33, and 78).
3.2.3.9 Float and Valve
The float and valve assembly serves 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
3-17
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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
emissions tend to give lower FTP emissions although statisti-
cal correlation between the measurements is poor (Ref. 60
and 84). The idle adjustment usually regulates by pass
(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 adjustment has
not been included in the after-market parts analyses since
it was not a physical part and problems with carburetor idle
adjustments are related to excessive emissions after-market
carbeuretors.
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
satisfactory 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).
3-18
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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 carbure-
tor which is closed by a solenoid and a thermal vacuum
valve. The thermal vacuum valve responds to coolant tempera-
ture 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 is
utilized to prevent engine stalling immediately following
the cold start. 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).
3.2.4 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
(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,
3-19
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16, 33, 74, 78, and 100). In some cases (i.e., distributor
advance mechanisms), the component performance may affect CO
or NO because of changes in ignition timing (Ref. 17, 92,
A
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
t Distributor cap
t Distributor rotor
• Mechanical advance
• Vacuum advance
• Distributor drive
• Dual diaphragm distributors
• Spark delay valve
• Magnetic/Optical triggers
t Spark plugs
• Igni tion wi res
• Coils
• Capacitive discharge systems
• Ballast resi stor
• Electronic ignition circuits
• Glow piug
t 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
3-20
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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.
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
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).
3-21
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3.3.2 Condenser/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)
3.3.3 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
• Mechanical advance
• Vacuum advance
• Distributor drive
• Dual diaphragm distributor
• Spark del ay 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
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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
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, modification
of the advance mechanism is relatively easy and constitues
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the after-market failure mode. Changing springs can advance
ignition timing and affect HC and NO emissions (Ref. 2
v /\
and 3).
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).
The ignition advance affects both HC and NO emis-
X
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
/\
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). Substitution of after-market vacuum
advance mechanisms can alter ignition timing although the
easiest method of advancing ignition timing is to advance
basic timing or switch from a ported vacuum source to a
manifold vacuum source.
3.3.3.5 Distributor Drive Mechanism
The distributor drive consists of the distributor
shaft, cam, and breaker arm. The distributor shaft is
3-24
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connected directly to the engine and is driven at one-half
of the 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).
3.3.3.6 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
3-25
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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).
3.3.4 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,
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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
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
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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).
3.3.7 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
A variety of capacitive discharge (CD) ignition
systems are sold for after-market, high performance applica-
tions. 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.
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The coil is able to output a higher secondary voltage which
is then distributed to the cylinders by a conventional
distributor (Ref. 3).
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
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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
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
J\
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
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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,
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). Timing adjustment was not
included in the after-market parts study since it is not a
physical component.
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.
/\
3.4.1 Thermostatically Controlled Air Inlet
Thermostatically controlled air (TAC) 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:
• Shroud and hose
• Thermostat
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• Vacuum motor and hoses
t Fresh air inlet
Failure of the TAG 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
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
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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.
3.4.1.3 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 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 acti-
vated; i.e., during 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
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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
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 Intake Manifolds
The OEM intake manifold generally is not replaced
except for unusual cases of manufacturing defects or to
install an after-market, specialty manifold. Intake manifolds
connect the carburetor to the cylinders and provide the
passages 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. Emission controlled
vehicles have connections between the exhaust and intake
manifolds. Specific emissions control components (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 a
manifold (Ref. 2 and 3). However, replacement of an OEM
manifold with after-market manifolds can result in emissions
increases although data on non-catalyst-equipped vehicles
suggest that some specific after-market manifolds do not
increase emissions (Ref. 104). The differences in emissions
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effect depends on the engine, manifold, and carburetor
combinations and the optimizing adjustments made.
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 generally 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.
After-market turbochargers may improve or degrade
emissions depending on the specific engine, carburetor, and
turbocharger combination.
Failure of an installed turbocharger results in
fuel enrichening 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 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 available on some diesel engines.
Supercharger kits are available for retrofit to spark ignition
engines.
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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).
After-market fuel injection components are distributed by
the OEM suppliers.
Fuel injection systems must fulfill the following
basic functions:
• Meter the correct quantity of fuel for the
speed and load condition.
• Inject the fuel at the correct time.
• Inject the fuel at the correct rate.
• Atomize the fuel into fine droplets.
t Distribute the fuel in the cylinder.
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.
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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
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
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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
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 indica-
ting a high air flow rate incorrectly. Both defects will
cause the EFI system to meter excessive fuel (Ref. 3, 27
and 58).
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In addition to air flow sensors, exhaust oxygen
sensors are also in use, or planned for use in conjunction
with three-way catalyst systems. The 02 sensors generally
have life expectancy similar to spark plugs. Their failure
should result in excess fuel metering, although most systems
have limited the range of enrichment controlled by the Op
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 tem-
perature 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).
3.5.8 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
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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).
3.5.11 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 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
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additional 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).
3.6 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.
t Camshafts.
After-market components, with the exception of
cams, lifters and springs, are designed and sold as OEM
equivalent parts. They are, therefore, expected to suffer
similar rates of deterioration and wear as the OEM components
The other components, however, can involve performance-
oriented nonstandard OEM replacement parts which can affect
emissions from the time of installation.
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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
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 and Camshafts
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.
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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).
Installation of after-market camshafts or grinding
of OEM cams which modifies the timing or degree of valve
opening can affect emissions.
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
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).
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3.6.1.5 Valves
The valves and seats in the cylinder must make a
tight seal at the correct time to ensure that the combustion
processes in the cylinder can be utilized efficiently without
excessive emissions. 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. 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
conditions, exhaust gases will escape from the cylinder
before combustion is complete causing generally higher HC,
CO, and smoke, but lower NO emissions (Ref. 3).
X
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
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).
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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
/\
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.
3.6.5 Exhaust Manifolds and Headers
OEM equivalent replacement exhaust manifolds and
specialty headers are available from after-market sources.
Replacement manifolds should have small affect on emissions.
Specialty manifolds or headers, however, may affect emissions
because of changes they create in mixture distribution
pumping efficiency and interconnection with various OEM
emissions control components and systems. Since emission
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changes may be different, separate component categories have
been established for replacement exhaust manifold and headers
3.7 EMISSION CONTROL SYSTEMS
A large number of systems and components have been
developed by or for engine and vehicle manufacturers specifi
cally to control emissions. Defects in these systems will
usually result in increased emissions of at least one pollu-
tant. Some systems are used on most engines and may be
available in the after-market. Others maybe used on only a
few engines or by a single manufacturer and are probably not
available in the after-market. In general, emission control
components available in the after-market are produced by the
same companies which manufacturered the equivalent OEM
component.
The following emission control systems and their
components are discussed in this section:
t Crankcase ventilation (PCV)
• Evaporative emissions (EVAP)
t Air injection (AIR)
• Exhaust gas recirculation (EGR)
• Transmission-controlled spark (TCS)
• Speed-controlled spark (SCS)
• Orifice spark advance control (OSAC)
• Electronic spark control (ESC)
• Catalytic reactor (CAT)
Most of the above systems use the same or similar
components. They are discussed individually, however, since
their effect on emissions may depend on their application.
Several individual components have been developed and are
discussed separately under Miscellaneous Emissions-Related
Parts:
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• Heat riser
0 Electric assist choke
t Staged choke pulldown
• Decel valve
• Distributor vacuum deceleration valve
t 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
manufacturer but generally include the following components:
• PCV valve
• PCV hoses
t PCV fresh air filter
• PCV oil separator
After-market PCV valves are available from a
number of mass merchandisers under private or brand labels.
These valves are sold as OEM replacement parts for specific
engines. Other PCV system components are also available.
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
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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
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 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.
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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
emissions (Ref. 3).
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 gener-
ally consists of the following components:
t Activated carbon canister
t Vacuum, vapor, and gasoline hoses and lines
• Fresh air filter
t Vapor-liquid separator
• Vapor control valves
EVAP system components are available to a limited
degree through the after-market.
3-49
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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).
3.7.2.2 EVAP Hoses and Lines
The EVAP 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 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
3-50
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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
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
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).
Add-on after-market fuel tanks which are not
adequately vented through the EVAP system may result in
increased evaporative emissions.
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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. Most air injection system components are
available from after-market distributors.
Air injection systems consist of the following
components:
• Distribution manifold and nozzles
• Hoses
• Inlet air filter
t Check valves
• Bypass or diverter valves
• Gulp val ves
• 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
since there is no significant emissions failure mode (Ref. 3)
They are not generally available in the after-market.
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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 (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). They are not
generally available in the after-market.
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
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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 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 and Belts
I
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
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system will be disabled causing higher HC and CO emissions
(Ref. 3 and 27). Air injection pumps are available through
the after-market from companies which manufacture the OEM
pumps and from rebuilders who refurbish used pumps.
3.7.4 Exhaust Gas Recirculation (EGR) Systems
Control of NO emissions is partly accomplished by
/\
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 .
A
Two 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 valves or orifices
t Hoses
t Temperature-controlled vacuum valves
• Solenoid-controlled vacuum valves
• Temperature switches
• Speed/transmission switches
• Time delays
t Vacuum amplifiers
t Vacuum-reducing valves
• Carburetor spacers
t Back pressure sensors
• Check valves
3.7.4.1 EGR Valves or Orifice
The fixed orifice or floor jet type EGR valve was
used only in a few engine families. Therefore, these systems
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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 particul ates, condensed water, and oil
in the exhaust gases. Failure of the EGR valve increases
NOV significantly (Ref. 2, 3, 27 and 86). Some EGR valves
y\
are available in the after-market; however, others are
available only through OEM parts distribution channels.
3.7.4.2 EGR Hoses
Hoses or tubes carrying the exhaust gases are
generally 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 as disabling the EGR system. This will
increase both HC and NO emissions (Ref. 3 and 27).
J\
3.7.4.3 EGR Temperature-Control1ed Vacuum Valves
Thermal vacuum valves (discussed in paragraph
3.7.9.7) are used in some applications to modulate EGR
during cold temperature operation. 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
A
Failure of the valve to close would slightly increase HC and
CO during warm up (Ref. 3 and 27). The characteristic
failure mode will be failure to open since it has the most
significant emissions failure.
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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. They are analogous to thermal
vacuum valves. Their failure will prevent any EGR (Ref. 3
and 27).
3.7.4.6 EGR Speed/Transmission Switches
Some systems modulate EGR in conjunction with
transmission gear position or speed. These systems are
often interconnected with timing retard systems. Their
failure will prevent EGR at any speed (Ref. 3 and 27).
3.7.4.7 EGR Time Delays
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.
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3.7.4.8 EGR Vacuum Amplifiers
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. A defective EGR
vacuum amplifier will create a large intake manifold vacuum
leak. This can affect performance and increase both HC
(misfire) and NO (no EGR) (Ref. 2, 3 and 27).
/\
3.7.4.9 EGR Vacuum-Reducing Valves
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).
3.7.4.10 EGR Carburetor Spacers
The carburetor spacer contains passages for
introducing the recirculated exhaust gases into the carbu-
reted mixture. The spacer does not usually deteriorate
significantly, however, the passages can become clogged with
exhaust gas particles or corrosion. The failure of the
spacer would increase NO because EGR flow would be reduced
A
(Ref. 3 and 27). These components are not generally avail-
able in the after-market since they are specific to parti-
cular engines.
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3.7.4.11 EGR Back Pressure Sensors
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. This increases the vacuum signal and results
in higher EGR. This valve can become clogged resulting in
reduced EGR at all times and, consequently, higher NO
A
(Ref. 3 and 27). These components are specific to particular
engines and are not available in the after-market.
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 Their failure will result in
/\
normal vacuum variations and a slight reduction in EGR
(Ref 3 and 27). These valves are similar to other vacuum
check valves and are available in the after-market.
3.7.5 Transmission-Controlled Spark (TCS)
Most manufacturers use transmission-controlled
spark systems to reduce timing advance during certain opera-
ting 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, in which case
the systems are referred to as SCS Systems. TCS systems
incorporate numerous protective and override systems and are
frequently interconnected with EGR systems.
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TCS systems consist of the various combinations of
the following components:
• Solenoid vacuum valve
• Vacuum lines and hoses
• Time delay control
• CEC solenoids
t Thermal vacuum valves
t Speed or transmission switches
t Reversing relays
• Temperature-controlled switches
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
X
times is the most critical failure mode (Ref. 3 and 27).
These solenoid valves are available in the after-market.
3.7.5.2 TCS Vacuum Lines and Hoses
The distributor advance unit is connected to the
manifold vacuum by a complex routing of vacuum lines. Any
leak in the lines will result in reduced vacuum advance
which will reduce NO and may create vacuum leaks resulting
X
in higher HC emissions due to lean misfire (Ref. 3 and 27).
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3.7.5.3 TCS Time Delay Controls
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 Solenoids
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 simul-
taneously 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).
J\
3.7.5.5 TCS Thermal Vacuum Valves
The TCS system may be modulated by several thermal
vacuum valves (discussed in paragraph 3.7.9.7) 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 (Ref. 3 and 27).
If they fail, they will most likely fail in the normal
operating position providing normal vacuum advance at all
times.
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3.7.5.6 TCS Speed or Transmission Switches
The TCS solenoid vacuum valve is actuated by a
transmission switch which senses road speed or gear selection
It is identical in nature and operation to the EGR speed/
transmission switch described above (Ref. 3 and 27).
3.7.5.7 TCS Reversing Relays
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 Switches
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 Orifice Spark Advance Control (OSAC)
The orifice spark control system is a method of
modulating vacuum advance used by one manufacturer. Replace-
ment parts are not generally available outside of authorized
OEM distributors. The system is used in conjunction with
EGR or TCS for control of NO . The system incorporates
/\
override systems during certain engine operating conditions.
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The OSAC system Incorporates the following
components:
• OSAC orifice valves
0 OSAC vacuum hoses
• OSAC vacuum control valves
• OSAC temperature sensors
3.7.6.1 OSAC Orifice Valves
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
NO (Ref. 3 and 27).
A
3.7.6.2 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).
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3.7.6.3 OSAC Vacuum Control Valves
The OSAC vacuum control valve is a thermal vacuum
valve (discussed in paragraph 3.7.9.7), which is used to
apply full manifold vacuum to the distributor advance unit
if the engine overheats. The higher manifold vacuum causes
higher engine rpm and improved cooling. The valve is located
in the cooling jacket or the radiator, depending on appli-
cation. Failure of the valve provides either delayed ported
or full vacuum advance at all times (Ref. 3 and 27).
3.7.6.4 OSAC Temperature Sensors
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
sensor bypasses the ported vacuum around the orifice in the
OSAC valve (Ref. 3 and 27).
3.7.7 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:
• Electronic modules
• Vacuum hoses/wires
• Solenoid vacuum valves
• Temperature-sensing switches
• Speed-sensing switches
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3.7.7.1 ESC Electronic Modules
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).
3.7.7.2 ESC Hoses/Wires
The solenoid vacuum valve is placed between the
manifold vacuum source and distributor advance unit.
Failure of the hoses will result in loss of advance to the
distributor and may create a vacuum leak causing high HC
(Ref. 27).
3.7.7.3 ESC Solenoid Vacuum Valves
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 NOX emissions
(Ref. 27).
3.7.7.4 ESC Temperature Sensing Switches
The ambient air switch overrides the speed modula-
tion of the distributor. Failure of the switch disables the
ESC system resulting in normal vacuum advance (Ref. 27).
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3.7.7.5 ESC Speed-Sensing Switches
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
/\
emissions HC and CO slightly (Ref. 27).
3.7.8 Catalytic Reactor
Most 1975 and 1976 model-year vehicles are equipped
with oxidation catalysts for control of HC and CO emissions.
Catalysts also permit some reduction of NO emissions as a
s\
consequence of richer carburetor adjustments. Catalysts are
not now available as after-market parts, although it is
conceivable that in the future they may become available.
Several dual catalyst and three-way catalyst
systems 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.
3.7.9 Miscellaneous Emissions-Related Parts
Several components are not specifically included
in any emissions control system. These parts include:
• Heat riser
• Electric assist choke
t Staged choke pulldown
t Decel valve
t Distributor vacuum deceleration valve
• Distributor starting solenoid
t Thermal vacuum valve
• Distributor vacuum valve
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3.7.9.1 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
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). Heat
risers are available through after-market sources.
3.7.9.2 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).
After-market choke heater components are available.
3.7.9.3 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
3-67
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fluid flowing through an orifice. This permits a vacuum
diaphragm connected to the choke plate to move. At tempera-
tures 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). After-market choke pulldowns are available.
3.7.9.4 Decel Valve
The decel valve is used to provides additional
carbureted mixture during periods of high intake manifold
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). After-market valves and parts
are available.
3.7.9.5 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 (high 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
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will cause increased NO emissions (Ref. 2, 3 and 27).
A
These valves are available through the after-market.
3.7.9.6 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). This component has limited usage
and is not generally available except from the OEM
distributors.
3.7.9.7 Thermal Vacuum Valve
All manufacturers use thermal vacuum valves in a
variety of applications. These valves usually sense coolant
temperatures either in the radiator or cooling jacket to
modulate vacuum signals controlling EGR, carburetor pulldown,
or spark advance. These valves are also called ported
vacuum switches (PVS), coolant temperature override (CTO)
valves, thermal ignition control (TIC) valves, and temperature
operated bypass (TOB) valves, depending on OEM vehicle
manufacturer and application. Thermal vacuum valves come in
numerous configurations such as two, three, four, and five
port valves and various temperature ranges (Ref. 3 and 27).
These valves are available through after-market distributors.
3.7.9.8 Distributor Vacuum Valve
The distributor vacuum valve is similar to the
distributor vacuum deceleration valve described above, but
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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 relation-
ship 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. The components
are associated with their respective engine or emission
control system even though this results in repetitive entries
of the same component categories in some cases.
3-70
-------
Table 3-1. EMISSIONS-RELATED
AFTER-MARKET PARTS
PARTS LIST
PART OR COMPONENT
Carburetor System
New Carburetors
Rebuilt Carburetors
Idle Stop Solenoid
Throttle Dashpot
Throttle Positioner
Metering Jets
Metering Rods
Vacuum Break Valves
Choke Mechanism
Accelerator Pumps
Power Valves
Gaskets
Float and Valve
Heat Riser
Idle Enrichment System
Electric Assisted Choke
Staged Choke Pulldown
Fuel Filter
Ignition System
Points
Con denser/ Capacitor
Distributor Cap
Distributor Rotor
Mechanical Advance Mechanism
Vacuum Advance Mechanism
Distributor Drive Mechanism
Magnetic or Optical Triggers
Spark Plugs
Ignition Wires
Coil - Inductive
Electronic (CD) Ignition
Ballast Resistor
Spark Delay Valve
Air Induction System
Thermostatical ly -Control led
Air Inlet
Vacuum Motor and Hoses
Air Cleaner Element
Intake Manifold
Turbochargers
Superchargers
RELATE!
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
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
X
X
X
EMISS
NOX
X
ION
Smoke
X
X
3-71
-------
Table 3-1. EMISSIONS-RELATED PARTS LIST
AFTER-MARKET 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
Engine System
Valve Lifters and Springs
Cams and Camshafts
Valves, Guides and Seats
Seal s
Rings
Gaskets
Exhaust Manifolds and Headers
Emission Control System
PCV Valve
PCV Hoses
PCV Fresh Air Filter
AI Distribution Manifold
AI Hoses
AI Inlet Filter
AI Check Valves
AI Bypass/Diverter 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
RELATED EMISSION
Ht
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
N0x
X
X
X
X
X
X
Smoke
X
X
X
X
X
X
X
X
X
X
3-72
-------
Table 3-1. EMISSIONS-RELATED PARTS LIST
AFTER-MARKET 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
3-73
-------
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 during Phase I on
OEM parts which selected the most emission-critical compo-
nents. 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). This model was modified during Phase II
A
to directly use values for each input factor. The general
flowchart of the model is shown in Figure 4-1. Specifically,
the model performed the following functions:
• Read-in data by part code.
• Calculate a criticality index (CI) by pol-
lutant for each part.
4-1
-------
READ IN
ASSIGNED
PARAMETER
VALUES
ARRANGE
DATA INTO
WORKING
ARRAYS
CREATE
WORKING
TAPE
LIST ASSUMED
VALUES BY
PART CODE
Figure 4-1. CRITICALITY MODEL FLOWCHART
4-2
-------
®
READ
INPUT
TAPE
DOE 5s
STANDARD
APPLY,
YES
NO
CALCULATE CI
ith POLLUTANTS
jth PART CODE
j=l,130
STORE
CI
Figure 4-1. CRITICALITY MODEL FLOWCHART (Continued)
4-3
-------
NO
1 = 1,4
RECALL
STORED
CI
LIST TOP 50
IN PRINCIPAL
SORT ORDER
LIST CI AND
RANK IN PART
NUMBER ORDER
C STOP J
CI
SAVE RANK
BY PART
CODE
Figure 4-1. CRITICALITY MODEL FLOWCHART (Continued)
4-4
-------
• Rank the CI values in descending order
t Print lists of rank-ordered parts by pollut-
ant .
The model can readily be expanded to include
additional component categories and pollutants or revisions
of the input parameter values.
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:
-------
V. Represented the sales volume factor for
the j component.
4-1.2 Emission Increase Factors
The emission increase factors (E..) were based on
the expected change in emissions with respect to the emission
standards applicable to the engines or vehicles using the
specific component. Emission increase factors were defined
for Federally certified engine families and Federal emission
standards. The values of E.. and corresponding emission
increase criteria are shown in Table 4-1.
Table 4-1. CRITERIA FOR EMISSION INCREASE FACTORS
E VALUF EMISSION INCREASE
0.0 No change or decrease in emissions
from defect (vehicle may be disabled
by defect in this component).
0.1 Emissions may increase but probably
not enough to fail standard.
1.0 Slight emission increase (enough to
fail standards).
2.0 Moderate emission increase (about
twice the standard).
5.0 Substantial emission increase
(several times the standard).
10.0 Severe emission increase (order of
magnitude higher than standard).
The emission increase factors used in Phase I were generally
used in Phase II. Different emission increase factors were
assigned to after-market components not included in the
Phase I analysis or which had different failure modes than
as OEM components. 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 configurations. The emission
increase factors for each component were assigned on the
assumption that other components were not defective.
4-6
-------
For the HC criticality rankings, the evaporative
emission increase factor for each component was combined
with the corresponding exhaust emission increase factor as
fol1ows :
EHC = EExhaust + 1/3 EEVAP
The smoke emission increase factors for each test
mode were averaged to provide a composite smoke emission
increase factor as follows:
E E E E
smoke = accel + lugging + peak
4.1.3 Probability of Failure Factors
The probability of a component's failure (PF.) prior
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.
The same factors assigned during Phase I were generally used
during Phase II. Some components, however, may have a
higher probability of failure as after-market parts than as
OEM parts because of incorrect calibration, application or
installation.
The 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
OEM manufacturer's recommended replacement interval of the
part, whichever was lower. Based on the available data and
engineering judgement, a relative factor representing the
probability of component failure was assigned using the
criteria shown in Table 4-2. The same PF. factors were
J
assigned to components for all model years.
4-7
-------
Table 4-2. CRITERIA FOR PROBABILITY OF FAILURE FACTORS
PF VTVtUt
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 1ife-
Failure very likely to occur during
component design life.
4.1.4
Probability of Repair Factors
The probabi1ity that a defective component would
not be repaired (PR.= ) prior to the end of its design life
was based on the detectabi1ity of the failure and the nature
of the component in relation to normal tune-up practice.
The same probability of repair factors used in Phase I were
used in Phase II. Components which had noticeable perfor-
mance effects (plugs) or were routinely replaced (condenser)
had a low probability of remaining defective. However,
defective components which were not normally serviced
(thermal vacuum valves) or had no noticeable effect on
performance (EVAP canister) would probably not be repaired.
The same PR. factor was assigned to all model-year vehicles.
Based on available data and engineering judgement, PR.
factors were assigned using the criteria shown in
Table 4-3.
4-8
-------
Table 4-3. CRITERIA FOR PROBABILITY OF REPAIR FACTORS
PR VALUE PROBABILITY OF REPAIR
0.10 Repair extremely likely due to severe
performance impact.
0.30 Repair likely due to performance
impact and routine diagnostic/service
procedures.
0.50 Repair may occur depending on diag-
nostic/service procedure and skill.
0.70 Repair unlikely due to small perfor-
mance impact or unusual failure mode.
0.90 Repair very unlikely due to small
performance impact and unusual
failure mode.
4.1.5 Sales Volume Factors
*
Sales volume data by component category was gener-
ally unavailable except for a few common after-market parts.
Published marketing data tended to reflect only generally
product areas and dollar volume. The large number of manu-
facturers and models of each component type precluded compila
tion of comprehensive unpublished data by the contractor.
Furthermore, most manufacturers were unwilling to provide
data on unit sales volume because of competitive concerns or
internal manpower required to compile the data.
Many components were used on several model years,
only some of which were subject to regulations. Many OEM
part vendors and vehicle manufacturers also distribute parts
in the after-market. Some components, such as vacuum switch-
ing valves, temperature sensors, and vacuum or air hoses may
be used in different applications which are not recorded at
point of manufacture and distribution.
Therefore, the criticality index model developed
in Phase I was modified to calculate a relative sales volume
factor as follows for each component:
4-9
-------
V,
where:
n. was a value representing the sales volume of
J tn
the j component.
Three independent sets of n. were developed and are described
J
in paragraph 4.2.4. These n. were based generally on the
following criteria:
0 Actual annual component sales by dealer-
ships, service stations, and independent
garages.
• Actual annual component sales by ware-
house distributors to retail parts stores and
repair facilities.
• Estimated annual component sales based on OEM
sales volume factors developed in Phase I.
The first two sets of sales volume factors were
based on published or surveyed sales data. The last set of
sales volume factors were based on sales volume factors
estimated from OEM component usage and recommended replace-
ment intervals.
4-10
-------
4.2 ASSIGNMENT OF CRITICALITY INDEX MODEL PARAMETERS
This paragraph describes the values of the CI
model input parameters assigned to each after-market compo-
nent. 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 summa-
rizes the input parameter values by part name.
4.2.1 Effect of Defect on Emissions
Each after-market component category was assigned
an emission increase factor for each of the following
pollutants:
0 Gasoline Engines
Evaporative hydrocarbons
Hydrocarbons
Carbon monoxide
Nitrogen oxides
• 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
4-11
-------
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
control system configurations corresponding to the different
emission standards.
4.2.1.1 Carburetion System
Carburetion systems include completely assembled
carburetors, carburetor components, and carburetor (throttle)
control devices. Complete carburetors are discussed in
addition to major components of the carburetor which are
subject to after-market adjustment or replacement. Specific
emission increase factors for HC, CO and NO are discussed
x
below for the following components categories based on the
functional description and characteristic defects described
in Section 3.2. The same emission increase factors were
assigned to components which can have similar effects on
carburetion.
• Assembled carburetors
New replacement
Rebuilt replacement
Performance modified
Carburetor control devices
Idle stop solenoid
Throttle dashpot
Throttle positioner
Carburetor components
Metering jets
Metering rods
Vacuum break valves
Choke mechanism (except electric assists)
Accelerator pump
4-12
-------
Power valve
Rebuilding kits
Float and needle valve
Idle adjustment
Idle enrichment systems
• Fuel filter
Assembled Carburetors: New or rebuilt replacement
carburetors are nominally identical to the OEM carburetor
that they replace. In some cases, the same carburetor model
as the OEM carburetor may be specified. In other cases, an
equivalent carburetor from a manufacturer other than the OEM
supplier may be specified. Unfortunately, emission certified
OEM carburetors have subtle differences in metering, power
enrichening, and vacuum ports which are not necessarily
present in after-market replacement carburetors, even though
they may appear physically identical. Therefore, emissions
may increase with respect to emission certification levels
on a particular vehicle even though they are lower than from
a defective OEM carburetor. The following emissions increase
factors for replacement carburetors were, therefore, assigned
on the basis of engineering judgment to reflect differences
in calibration if compared to OEM certified carburetors.
^ ^
1972-1974 1.0 2.0 0.1
1975 1.0 2.0 0.1
After-market carburetors are available which
promise improved performance, driveability or fuel economy
relative to the OEM carburetor. These after-market carbure-
tors are usually recalibrated or employ different components
than the stock OEM carburetor. These differences result in
mixture enrichment during accelerations and open throttle
4-13
-------
HC_
1.0
2.0
CO.
2.0
5.0
NOX
1.0
1.0
operation. Components which may differ from the OEM configura-
tion include accelerator pump stroke, float adjustment,
power enrichment, metering jet size, metering rod size or
adjustment, venturi vacuum depression, and the location of
and vacuum signals from spark timing and EGR ports. A
recent study by the California Air Resources Board (Ref. 108),
indicated that substantial emission increases on pre-1975
model year vehicles could occur from a performance carburetor.
Higher emission increase factors were assigned to late model
vehicles because the large emission increase expected and
lower emission standards relative to pre-1975 model year
vehicles.
1972-1974
1975
Carburetor Control Devices: These control include
the idle stop (anti-dieseling) solenoid and dashpots or
positioners for deceleration control. The idle stop solenoid
defect would result in excessive throttle closure (anti-
dieseling) during idling. This results in low engine speed
and rich operation at idle. An improperly adjusted idle
stop solenoid was identified as the cause of an HC 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 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.
Defective dashpots result in more rapid throttle
closure during deceleration. Defective throttle positioners
result in full throttle closure during decelerations. These
4-14
-------
defects result in momentary mixture enrichment (Ref. 3)
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.
Throttle control devices generally affect idle
mixture and are analogous to improper idle adjustment. The
emissions increase resulting from defects or improper adjust-
ment depends on the degree of misadjustment, engine size,
and emission control system. Rich operation, however, is
common as shown by surveillance and inspection programs
(Ref. 12, 16, 78, and 94).
Therefore, the following emission increase factors
were assigned to throttle control devices (idle stop solenoids,
throttle dashpots and throttle positioners) on the basis of
a moderate enrichment (1 to 2 percent CO at idle):
H£ CO^ N0^x
1972-1974 0.1 1.0 0.0
1975 1.0 1.0 0.0
Carburetor Components: Failures in carburetors
are generally related to defects or misadjustments of one or
more of the following specific components. In addition,
most of these components are individually available from
after-market distributors and retailers. Components which
tend to have the same magnitude of emissions increase have
grouped together.
Components with relatively moderate influence on
overall emissions include incorrect metering jet size,
metering rod adjustment, and accelerator pump stroke. No
specific data on the relationship of these components to FTP
emission levels was obtained. However, the general result
of after-market modification or replacement of these compo-
nents is probably mixture enrichment relative to the OEM
4-15
-------
HC.
0.1
0.1
CO
2.0
2.0
NOY
'"" "A
0.0
0.0
configuration. Although post-1975 model year vehicles are
probably more sensitive to these changes than pre-1975 model
year vehicles as a result of the more stringent emission
standards, these components were assigned the following
emissions increase factors on the basis of engineering
judgment:
1972-1974
1975
Defective or improperly adjusted 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 may also increase since
the vacuum is below the throttle plate (Ref. 27) and lean
misfire can occur during closed throttle. The following
emission increase factors were, therefore, assigned:
1972-1974
1975
The choke, power valve, float, and needle valve
can all significantly affect carburetion if defective or
improperly installed or adjusted. These components can
cause higher HC and CO emissions particularly during open-
throttle operation. The degree of emission increase depends
on engine size, and emission control system and nature of
defect or mi sadjustment. This defect may also result in
accelerated catalyst aging for catalyst-equipped vehicles as
4-16
HC^
0.1
1.0
cp.
1.0
1.0
N0y
"A
0.0
0.0
-------
HC
—
2.0
2.0
CO.
10.0
10.0
NOV
— x
0.0
0.0
well as higher emissions (Ref. 12, 16, 17, 70, 78, 92, 93
and 100). The HC/CO emission increase factors were, there-
fore, assigned as follows:
1972-1974
1975
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, however, the failure is
expected to cause slight emission increases of HC from none
catalyst-equipped vehicle and slight HC and CO emission
increases from catalyst-equipped vehicles. Therefore, the
following emission increase factors were assigned on the
basis of engineering judgment:
1972-1974
1975
Gaskets, vacuum diaphragms, needle valves and
other carburetor components are generally sold in rebuilding
kits rather than individually. Carburetor kits are instal-
led in carburetors by the vehicle owner or a mechanic. The
rebuilding process requires disassembly of the carburetor,
complete cleaning in solvents, and reassembly, reinstal1ation
and final adjustment of the carburetor. The carburetor kit
components generally are not defective, however, the chance
of reassembling and readjusting the carburetor to give the
same emissions performance is relatively low. Therefore,
the same emissions increase factors assigned to factory
rebuilt carburetors were assigned to carburetor kits:
4-17
HjC
0.1
0. 1
co.
0.0
0.1
— x
0.0
0.0
-------
1972-1974 1.0 2.0 0.1
1975 1.0 2.0 0.1
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
assigned for throttle control devices were, therefore,
assigned:
H
-------
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.
The following after-market ignition system compo-
nents are discussed below:
• Points
• Condenser
• Distributor cap
• Distributor rotor
t Distributor mechanical advance
t Distributor vacuum advance
• Spark delay valves
• Electronic ignition triggers
• Spark plugs
0 Ignition wires
• Coils
t Ballast resistor
• Electronic ignition circuits
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
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.
4-19
-------
After-market ignition components are sold under
many brand names and private labels. After-market replace-
ments are generally available for OEM ignition components.
In addition, after-market components are also available
which offer improved performance, durability or fuel economy
than the OEM configuration components. After-market electronic
ignition retrofit kits are the best example of this component
category. In general, the same basic design and operating
characteristics are found in OEM and after-market ignition
components. Therefore, the modes of failure and the resulting
emission increases for after-market components were based on
the analysis of OEM components.
Primary Ignition Components: The primary ignition
system includes points, condenser, coil, CD ignition system,
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 NOV (Ref. 12, 78, and 94). On catalyst-equipped
/\
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
A
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:
4-20
-------
Hi
1.0
0.1
CjO
0.0
0.1
— x
0.0
0.0
1972-1974
1975
Distributor Rotor and Cap: A defective distributor
cap and/or rotor increases the resistance of the secondary
ignition circuit and reduces the available firing voltage at
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 basic timing which can effect HC, CO and NO emis-
/\
sions depending on engine speed and/or load 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.
After-market distributor springs and weights are
likely to have a different advance curve than OEM springs.
In particular, after-market advance springs are sold which
intentionally increase the spark advance at a given speed in
order to improve acceleration and performance. This would
Mi
2.0
2.0
CO.
0.0
0.1
NlDx
0.0
0.0
4-21
-------
HC_
0.1
0.1
co.
0.1
0.1
NOX
1.0
1.0
be expected to increase HC and NO emissions and possibly
/\
reduce CO emissions (Ref. 16, 17, and 100). An EPA study,
however, indicated that a commercial after-market distributor
spring did increase NO (30 percent) and HC (13 percent) but
/\
also increased CO (12 percent). These tests were based on
hot start tests on noncatalyst-equipped vehicles. Although
the HC, CO emissions increases are low, the NO emission
A
increase could result in an emission failure.
1972-1974
1975
After-market vacuum advance mechanisms are more
likely to result in retarded advance than after-market
mechanical advance mechanisms. This is because advance
mechanisms are interchangeable over several model years and
more recent components tend to be more available. Recent
vacuum advance characteristics tend to be more retarded than
early curves so that it is more likely to obtain retarded
timing. Actual failure of the vacuum diaphragm will also
cause retarded timing. Emissions of HC decrease due to late
firing and smaller surface to volume ratios. Emissions of
NO decrease due to the combustion occurring at lower compres
/\
sion ratios than normal. Emissions of CO increase because
additional throttle angle is required and mass flow rates
are higher. The following emission increase factors were,
therefore, assigned to distributor advance mechanisms.
HC_ CjO N0.x
1972-1974 0.0 0.1 0.0
1975 0.0 1.0 0.0
Spark Delay Valves: After-market spark delay
valves may be bypassed, missing, or incorrect for the appli-
cation. This will generally result in normal vacuum advance
4-22
-------
during initial throttle opening which increases NO emissions
A
and may also 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 defec-
tive OSAC valves since they result in advanced timing.
HC. C_0 N^x
1972-1974 0.1 0.0 1.0
1975 0.1 0.0 1.0
Electronic Ignition Trigger and Control Circuits:
Several after-market retrofit kits for electronic optical or
magnetic sensing of spark timing are available. 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:
1972-1974
1975
Spark Plugs/Mires: 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
Cg, 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
A
increase but not enough to fail (Ref. 16, 78, 92, 93, and
100). On catalyst vehicles, the excess HC emissions may be
HC.
10.0
10.0
C_0
0.0
0.1
HO
A
0.0
0.0
4-23
-------
HC.
10.0
10.0
CO.
0.0
0.1
N0x
0.0
0.0
partially oxidized to CO. Therefore, the following emission
increase factors were assigned to defective plugs and wires:
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:
• Thermos tatic Air Cleaner (TAG) including
shroud and hose, thermostat, vacuum motor,
vacuum hoses, fresh air inlet
• Air cleaner element
• Manifolds
• Turbocharger and supercharger
Except for turbochargers, superchargers and mani-
folds, after-market components are essentially OEM equivalent
Therefore, failure modes and emission increases resulting
from failures were the same as for OEM components.
TAG 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
/\
be negligible. Vehicles equipped with catalysts are more
sensitive to cold start emissions. Therefore, the following
emission increase factors were assigned to these components:
4-24
-------
1972-1974 0.1 0.0 0.0
1975 1.0 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
/\
(Ref. 92 and 93). The following emission increase factors
were, therefore, assigned:
NO
A
0.0
0.0
TAC Fresh Air Inlet: A defective TAC 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
HC.
0.1
1.0
CO
0.0
0.1
4-25
-------
1972-1974 0.1 0.1 0.0
1975 0.1 0.1 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), has
/\
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 configure'
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
— x
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 PEAK
1972-1973 1.0 0.0
1974-1975 1.0 0.0 1.0
4-26
-------
Manifolds: After-market manifolds are sold as OEM
replacement or specialty. The replacement manifolds are
dimensionally and materially equivalent to the original OEM
manifold. The specialty manifolds have differing configura-
tions and are typically sold for use in conjunction with air
after-market specialty carburetor. Two reports documented
the effect of changes in manifold. One study (Ref. 105),
indicated that emissions from pre-1975 model year vehicles
could either increase or decrease slightly depending on the
specific manifold and engine. The second study (Ref. 108)
indicated that an after-market manifold installed on a 1974
model year vehicle did not significantly affect emissions.
No data, however, was available for catalyst-equipped vehi-
cles. Therefore, the following emissions increase factors
were assigned for after-market intake manifolds:
HiC CO^ fiO
1972-1974 0.1 0.1 0.0
1975 0.1 0.1 0.0
Turbocharger and Supercharger: The turbocharger
and supercharger increases the volumetric efficiency of the
engine due to pressurizing the intake manifold (Ref. 2).
The turbocharger only functions during acceleration or high
load conditions, however, the supercharger operates at all
times. Defective or improperly sized units would be expected
to reduce the air pumped through the engine and, thereby,
result in mixture enrichment (Ref. 2). The emission increase
factors are shown below:
HC CO NO
1972-1974 1.0 2.0 0.0
1975 1.0 2.0 0.0
4-27
-------
ACCEL LUGGING PEAK
1972-1973 1.0 0.1
1974-1975 1.0 0.1 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.
After-market fuel injection systems are distributed
by the same companies which sell to the OEM vehicle and
engine manufacturers utilizing fuel injection systems.
Replacement parts for these systems are distributed by the
vehicle manufacturers as well as through the after-market by
the fuel injection manufacturers. The after-market components
are, therefore, OEM equivalent replacement parts with the
same failure modes and emission increases as for the OEM
component.
The following fuel injection components are dis-
cussed below:
0 Accumulator
• Fuel pressure sensors/regulators
• Throttle linkage and valve
t Injection valves
• Air sensors/switches
t Temperature sensors/switches
• Injectors
4-28
-------
t Triggering switches
t Starting valve
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
emissions as follows:
1972-1973
1974-1975
ACCEL
0.1
0.1
LUGGING PEAK
0.1
0.1
0.1
Fuel Pressure Sensor/Regulators: 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 the FTP. Therefore, the following emission increase
factors were assigned:
1972-1974
1975
HC_
0.1
0.1
C_0
1.0
1.0
N0.x
0.0
0.0
1972-1973
1974-1975
ACCEL
1.0
1.0
LUGGING PEAK
0.1
0.1
1.0
Throttle 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
4-29
-------
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:
ACCEL LUGGING PEAK
1972-1973 1.0 0.1
1974-1975 2.0 0.1 " 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 PEAK
1972-1973 1.0 1.0
1974-1975 1.0 1.0 2.0
Air Flow or Temperature Sensors/Switches (EFI):
Characteristic defects in air or oxygen sensors/switches
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 Op 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
— x
0.0
0.0
4-30
-------
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
NOV
— 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
Hi
2.0
2.0
CO
0.1
1.0
NO
0.1
0.1
Starting 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:
Hi C_i Mix
1972-1974 1.0 5.0 0.0
1975 1.0 5.0 0.0
4-31
-------
4.2.1.5 Engine Systems
The following after-market engine components are
emissions-related:
• Exhaust valves and associated components such
as seals, lifters, springs, guides, cams,
camshafts and timing chains.
• Piston rings.
• Head gaskets.
• Exhaust manifolds/headers.
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.
/\
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. Performance engine components can
also affect emissions, however, the increases are no worse
than from defects in the OEM components (Ref. 105). The
following emission increase factors were, therefore, assigned
to all internal engine components using engineering judgment:
4-32
-------
Hi CO^ N0_x
1972-1974 1.0 1.0 0.0
1975 0.1 0.1 0.0
ACCEL LUGGING PEAK
1972-1973
1974-1975
1.0
1.0
1.0
1.0
1.0
4.2.1.6 Emission Control Systems
In general , there are no after-market sources of
emission control system components since the same vendors
sell the same components both to OEM vehicle manufacturers
and to after-market parts distributors under private labels.
Therefore, the same emission increase factors established
for OEM components were used for after-market components.
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.
X
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)
4-33
-------
• Air injection (AIR)
• Exhaust gas recirculation (EGR)
• xTransmission/speed controlled spark (TCS)
• Orifice spark advance control (OSAC)
• Electronic spark control (ESC)
0 Catalytic reactor (CAT)
• Manifold heat control (Heat riser)
• Electric assist choke
• Staged choke pulldown
0 Decel valve
0 Distributor vacuum deceleration valve
0 Thermal vacuum valve
0 Distributor starting solenoid
0 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 contribues 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
/\
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
HC
0.1
1.0
cp_
1.0
1.0
N0x
0.0
0.0
PCV and EVAP Vacuum Hoses: PCV or EVAP hose
failure (rupture or looseness) results in evaporative emis-
sions and possibly lean misfire. Under high load, crankcase
vapors may be forced into the atmosphere. If an intake
4-34
-------
manifold vacuum hose fails, a lean misfire will result due
to the high air flow at idle (Ref. 3). Catalyst vehicles
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
NO
A
0.0
0.0
EVAP Canister: 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
X
0.0
0.0
EVAP 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 separa-
tor, or fuel tank cap. The following emission increase
factors were assigned to the above EVAP system components on
the basis of engineering judgment:
4-35
-------
1974-1974
1975
EVAP
2.0
2.0
HC
0.0
0.0
CO
0.0
0.0
NO
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
NOX emissions. Failure of the AI system on catalyst vehicles
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
HJL
1.0
2.0
C_0
1.0
5.0
— x
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
H£
0.1
1.0
C£
0.1
1.0
NO
" ""A
0.0
0.0
Air 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,
/\
4-36
-------
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
Hi
0.1
2.0
CO
0.1
5.0
— x
0.0
0.0
EGR 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
/\
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
NO
— x
2.0
2.0
EGR 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
4-37
-------
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,
and Back 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 mani-
folds. 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
c_i
0.0
0.0
NO
A
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:
4-38
-------
HC_ CO^ N£
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
A
produce normal vacuum advance at all times. This results in
a slight HC emission increase and substantial NO increases.
A
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 assigned:
H C CO NO
1972-1974 0.1 0.0 2.0
1975 0.1 0.0 2.0
TCS, 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
A
increased 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):
HC CO NO
1972-1974 0.1 0.1 0.0
1975 0.1 1.0 0.0
4-39
-------
CEC 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:
y\
HC_ C_0 N£x
1972-1974 2.0 2.0 0.0
Orifice Spark Advance Control (OSAC) 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
y\
equipped with OSAC also have other controls; i.e., E6R or
TCS (Ref. 3 and 27). The following emission factors were,
therefore, defined:
N0x
2.0
1.0
Catalytic Reactors (CAT): Catalytic reactors are
not presently available in the after-market nor is after-
market distribution planned in the foreseeable future by any
manufacturer. Therefore, catalysts are not included in this
analysis.
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
1972-1974
1975
H_C
0.1
0.1
CO
0.0
0.0
4-40
-------
closed position (hot manifold) which would delay the warm-up
of the intake manifold and cause lean misfire due to vaporiza
tion 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
CO
0.0
0.1
N0v
— x
0.0
0.0
Electric Assisted 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
A
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
riox
0.0
0.0
Decel Valve: 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:
1972-1974
1975
HC
0. 1
1.0
co.
1.0
1.0
NO
0.0
0.0
4-41
-------
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
NO
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
Mi
1.0
1.0
co.
1.0
1.0
N0x
0.0
0.0
Thermal Vacuum Valve: 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 TVV has been included in those cate-
gories. Failure of a TVV results in normal spark advance at
all temperatures. Therefore, the following emission increase
factors were assigned:
1972-1974
1975
HC
0.1
0.1
CO.
0.0
0.0
N0v
— x
2.0
2.0
4-42
-------
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
NOX
0.1
0.1
4.2.2 Probability of Component Failure Factor
Each component category was assigned a factor
representing the probability of failure between installation
and expiration of the vehicle OEM emission warranty or the
component design life. Supporting data were either unavail-
able or contradictory- Therefore, the factors were assigned
based on the general criteria discussed in paragraph 4.1.3.
The same probability factors were assigned to similar compo-
nents (i.e.; TVV, speed sensors) even if they were used in
different applications. In determining the values for
failure probability, consideration was given to the following
factors :
• Operating environment (temperature, gas
characteristics)
• Normal operating state (activated, deactivated)
• Operating principle (vacuum, mechanical,
electrical)
• Similarity to OEM component
t Need for adjustment, calibration, or alignment
at time of installation
4-43
-------
4.2.2.1 Carburetion Systems
In addition to normal component deterioration,
after-market carburetor components are subject to defects
in installation which can result in a failure condition
existing from the time of installation. The probability of
failure at installation or shortly thereafter is relative
with, nominally OEM replacement carburetors having the lowest
probability of failure (PF=0.30), factory rebuilt carburetors
having a higher probability of failure (PF=0.50), and mechanic
or owner rebuilt carburetors having a relatively high pro-
bability of failure (PF=0.70).
Carburetor components and control devices are
generally quite reliable and are not usually reported as
becoming 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 electrical or mechanical components
were assigned a low probability of failure (PF=0.10) on the
basis of their passive function and freedom from adjustment.
The fuel filter is a standard replacement part with recom-
mended replacements every 2 years. These components are
rarely, if ever, associated with emissions failures (Ref. 12,
16, 78, 94, 101 and 102):
• Electric assist choke heaters
• Idle enrichment systems
• Metering jets
• Gaskets
• Fuel filters
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:
4-44
-------
t Idle stop solenoids
• Throttle dashpots and positioners
• Metering rods
• Choke mechanisms
t Float and needle valves
• Accelerator pumps
• Power valves
• Vacuum break valves
t Staged choke pulldowns
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), freedom
from initial adjustment, and broad performance tolerances
before misfire actually occurs:
• Condensers
t Distributor drive mechanisms
• Electronic ignition triggers
• Coils
• Bal1ast resi stors
• Electronic ignition (CD) circuits
The following primary ignition system components
were assigned a slightly higher probability of failure
4-45
-------
(PF = 0.30) based on more rapid deterioration due to severe
operating conditions or lose of modification. These compo-
nents, however, are designed to last the certification
period (Ref. 70):
t Ignition wires
• Distributor caps and rotors
t Distributor mechanical advance mechanisms
t 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 and the need to carefully install and adjust them:
• Points
t Spark delay valves
The following component was assigned a relatively
higher probability of failure (PF=0.70) based on durability
data, garage experience and PVIM data.
• Spark plugs
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.
The following air induction components were assigned
a low probability of failure (PF=0.10) based on their
durability:
4-46
-------
• TAG shrouds and hoses
• TAC thermostats
t Turbochargers
The following air induction components were assigned
a slightly higher probability of failure (PF=0.30) based on
more rapid deterioration or less durable construction.
• TAC vacuum motors
• TAC vacuum hoses
• TAC fresh air inlets
• Superchargers
After-market specialty intake manifolds were
assigned a relatively high probability of an emissions
increase (PF=0.5) on the basis of published data.
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 desi gn .
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
vari ations :
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:
4-47
-------
• Pressure sensors/regulators
• Air sensors/switches
• Temperature sensors/switches
t Triggering switches
• Electronic fuel injection circuits
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)
• Injection valves
• Solenoid injectors
• Starting valves
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 end of the certification period:
t Valve cam lobes
t Valve guides
• Piston rings
• Gaskets
0 Camshafts
t Exhaust manifolds and headers
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)
was assigned to failure of the valve lifters and springs
4-48
-------
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 para-
graphs 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 vehi-
cle. 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).
4-49
-------
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 Check Valves - 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,
Sensors, 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).
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)
4-50
-------
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. These factors were the same as defined
for OEM components since the symptoms of failure for after-
market components are similar. 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 carburet ion-related components, with the
exception of the fuel filter and idle adjustment, are not
included in scheduled maintenance. Carburetor replacement
or rebuilding is usually performed when noticeable performance
degradation occurs which can be attributed to leaking or
sticking components. 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).
• New or rebuilt replacement carburetors
t Metering jets
• Metering rods
• Chokes
4-51
-------
• Gaskets
• Float and valve
• Idle enrichment systems
• Vacuum break valves
t Power valves
• Accelerator pumps
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
t Dashpot
t Throttle positioner
The fuel filter is usually replaced during scheduled
tune-ups (Ref. 3, 27, and 101). A low probability of no
repair (PR=0.30) was therefore assigned.
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
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
4-52
-------
probability of not replacing these components was, therefore,
quite high (PF=0.90).
• Distributor drives
• Spark delay valves
• Coils
• Ballast resistors
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).
• Mechanical advances
• Vacuum advance including dual diaphragm
distributors
t Ignition wires
t Distributor rotors
• Distributor caps
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
• Condensers
• Electronic ignition trigger switches
• Spark plugs
• Electronic ignition circuits
4-53
-------
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).
t TAG shrouds and hoses
• TAG thermostats
• TAG vacuum motors
• TAG vacuum hoses
• TAG fresh air inlets
• Intake manifolds (OEM replacement or specialty)
Turbochargers and superchargers 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
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:
4-54
-------
• Accumulators
0 Fuel pressure sensors/regulators
• Throttle linkage and valves
t Injection valves
• Injectors
t Temperature sensors/switches
• Fuel distribution manifolds
• Starting valves.
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).
t Air sensors/switches
• Triggering switches
• Electronic fuel injection control circuits
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
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.
4-55
-------
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).
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).
4-56
-------
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, Belts 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.
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).
4-57
-------
EGR 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).
Thermal 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).
Heat 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
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
Valve - 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.
4-58
-------
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
Actual component sales data were not available for
most of the component categories for the reasons stated in
Section 2. This data was, however, estimated from three
independent sources which provided three alternative critical
ity rankings. The three sources were the following:
• Component usage based on OEM engine con-
figurations, recommended replacement inter-
vals and sales volumes
t Service and repair actions reported by
commercial garages
• Component sales by warehouse distributors
The input values assigned to each set of these
sales volume factors are discussed below and are tabulated
in Table 4-4. Appendix B presents the relative sales volume
factors derived from the sales volume input factors.
4.2.4.1 OEM Sales Volume Factors
These sales volume factors were developed during
Phase I (Ref. 107). The input factors used in Phase II
represent the sum of the 1972-1974 model year and 1975 model
year sales volume factors tabulated in the Phase I final
report. The after-market OEM sales factors were multiplied
by 100 to give them the same scale as for after-market
warehouse and garage sales factors. The development of the
OEM sales factors is described in the Phase I final report.
Briefly, however, they were based on the following criteria:
4-59
-------
Table 4-4. SALES VOLUME FACTORS
PART
CODE
1. 1. 1
1. 1. 2
1. 1. 3
1. 2. 1
1. 2. 2
1. 2. 3
1. 3. 1
1. 3. 2
1. 3. 3
1. 3. 4
1. 3. 5
1. 3. 6
1. 3. 7
1. 3. 8
1. 3. 9
I. 3.10
1. 3.11
1. 4. 0
2. 1.
2. 2.
2. 3. 1
2. 3. 2
2. 3. 3
2. 3. 4
2. 3. 5
2. 3. 6
2. 3. 7
2. 4. 0
2. 5. 0
2. 6. 3
2. 7. 0
2. 8. 0
2. 9. 0
2.10. Z
2.11. 0
3. 1. 1
0
0
PART NAME
NEW CARB
REBUILT CARB
SPECIALTY CARB
IDLE STPSOLENQIO
THROTTLE DASHPQT
THRTTL POSITICNR
METERING JETS
METERING RODS
VAC BRK VALVE
CHOKE MECHANISM
ACCELERATCR PUMP
POWER VALVES
GASKETS
REBUILDING KITS
FLOAT AND VALVE
IDLE ADJUSTMENT
IDLE ENRICHMENT
FUEL FILTER
POINTS
CONDENSER
CAP
ROTOR
MECH ADVANCE
VACUUM ADVANCE
DISTRIBUTOR DKIV
DUAL DIAPHM DIST
SPARK DELAY VLV
MAG/OPT TRIGGERS
SPARK PLUGS
IGNITION HIRES
COIL
CAPACITIVE DISCH
BALLAST RESISTOR
El CONTROL CIRCT
IGN TIMING ADJ
TAC SHROUD
OEM
SALES
99
99
5
75
14
7
181
69
100
98
99
98
98
99
99
0
3
381
231
68
98
99
5
99
99
5
43
31
4283
716
99
5
99
31
99
97
SALES
GARAGE
SALES
1515
2567
75
0
0
0
0
0
0
0
0
0
0
8217
8271
0
0
36313
61200
61200
61200
61200
0
0
0
0
0
4868
414481
92604
0
0
0
4868
17252
0
DATA
WAREHOUSE
SALES
83164
80112
4158
16600
8567
0
0
0
17844
43514
0
0
0
82236
0
0
0
129057
179332
179332
93636
109916
2400
10260
12800
0
20200
4C8
3903000
138668
28980
1440
0
3600
0
16000
SALES VOLUME FACTORS
OEM GARAGE WAREHOUSE
SALES SALES SALES
0.
0,
0.
0.
0.0062
O.GC62
O.C003
O.CC47
O.CC09
O.C004
0.0114
O.G043
O.CC63
O.C062
O.C062
O.CC62
,0062
CC62
,0062
r.C
0.0002
O.C240
O.C146
O.CC43
.0062
,0062
,CC03
.GC62
.OC62
O.GG03
0.0027
O.CG20
0.2700
O.Q451
O.CC62
O.C003
O.G062
0.0020
O.GC62
0.0061
0,
0,
0,
0,
0,
0.0014
0.0024
0.0001
O.G
0.0
0.0
0.0
G.O
0.0
c.o
O.C
Q.O
0.0
O.C075
Q.G076
G.O
0.0
C.0333
C.0561
0.0561
0.0561
0.0561
C.O
0.0
O.C
0.0
0.0
0.0045
0.3802
0.0849
0.0
0.0
0.0
0.0045
0.0158
0.0
0.0136
0.0131
0.0007
0.0027
0.0314
0.0
0.0
0.0
0.0029
0.0071
0.0
0.0
0.0
0.0134
0.0
0.0
0.0
0.0211
0.0293
0.0293
0.0153
0.018C
0.0004
0.0017
0.0021
0.0
0.0333
0.0001
0.6374
0.0226
0.0347
0.0002
0.0
0.0006
0.0
0.0026
-------
Table 4-4. SALES VOLUME FACTORS (Continued)
PART
CODE
en
3. 1. 2
3
4
3. 1.
3. 1.
3. 1. 5
3. 2. 0
0
0
0
3. 3.
3. 4.
3. 5.
4. 1.
4. 2. 0
4. 3. 0
4. 4. 0
4. 5. 0
4. 6. 0
4. 7. 0
4. 8. 0
4. 9. 0
4.10. 0
4.11. 0
4.12. 0
4.13. 0
5. 1. 1
5. 1. 2
5. 1. 3
5. 1. 4
5. 1. 5
5. 2. 0
5. 3. 0
5. 4. 1
5. 5. 0
6. 1. 1
6. 1. 2
6. 1. 3
6. 1. 4
6. 2. 1
6. 2. 2
PART NAME
TAC THERMOSTAT
TAC VAC MOTOR
TAC VAC HOSES
TAC FRESH AIR IN
AIR CLEANER ELEM
INTAKE MANIFOLD
TURBOCHARGER
SUPERCHARGER
MFI ACCUMULATOR
FI HI PRES PUMP
FI PRES SENS/KEG
FI THROTTLE VALV
MFI VALVES
EFI AIR SENS/SWH
EFI TEMPSENS/SWH
FI DIST MANIFOLD
EFI INJECTORS
EFI TRIGGER SWCH
EFI CONTROL CIRC
FI STARTING VALV
FI IDLE ADJUST
VALVE LIFTER/SPR
VALVE CAM LOBES
VALVE GUIDES
VALVE SEALS
EXHAUST VALVES
PISTON RINGS
PISTON/RODS
HEAD GASKETS
CAMSHAFTS
PCV VALVE
PCV HOSES
PCV FRSHAIR FLTR
PCV OIL SEPARATR
EVAP CANISTER
EVAP HOSES
GEM
SALES
97
83
83
1
335
5
1
1
0
1
1
1
4
0
0
1
1
0
0
1
0
750
37
725
725
725
725
725
173
5
343
99
244
2
101
99
SALES
GARAGE
SALES
0
0
0
0
53109
0
0
0
0
11
0
0
0
0
0
0
0
0
0
0
0
17419
873
13248
13248
19248
33726
0
2716
873
35778
0
0
0
0
0
DATA
WAREHOUSE
SALES
6800
10000
8476
600
189956
888
0
0
0
1121
0
2400
0
0
0
0
0
0
0
0
0
111097
3404
62544
62544
62544
61312
17468
61920
61312
109660
0
43344
0
0
0
SALES VOLUME
OEM
SALES
0.0061
O.C052
O.CC52
O.CCQ1
O.C211
O.CCQ3
O.CC01
O.C001
o.c
O.CC01
O.OC01
O.C001
0.0003
0.0
o.c
0.0001
O.C001
0.0
o.c
0.0001
0.0
O.C473
O.OC23
0.0457
0.0457
0.0457
0.0457
0.0457
0.0109
O.C003
0.0216
O.CQ62
0.0154
O.C001
0.0064
O.C062
GARAGE
SALES
O.C
0.0
O.C
0.0
0.0487
0.0
o.c
0.0
0.0
0.0000
0.0
0.0
0.0
o.c
0.0
0.0
0.0
o.c
c.c
c.c
0.0
0.0160
C.0008
0.0122
0.0122
0.0177
0.0309
0.0
0.0025
C.0008
0.0328
0.0
0.0
0.0
0.0
o.c
FACTORS
WAREHOUSE
SALES
0.0011
0.0016
0.0014
O.O^Ol
0.0310
0.0001
0.0
0.0
0.0
O.OC02
0.0
0.0004
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
o.c
0.0181
0.0006
0.0102
0.0102
0.0102
0.0100
0.0029
0.0101
0.0100
0.0179
0.0
0.0071
0.0
0.0
0.0
-------
Table 4-4. SALES VOLUME FACTORS (Continued)
ro
PART PART NAME OEM
CODE SALES
6. 2. 3 EVAP FRSM AIR 271
6. 2. 4 EVAP VPRLIG SEP 97
6. 2. 5 EVAP VAPOR CCNTR 49
6. 2. 6 FUEL TANK/CAP 98
6. 3. 1 AI MANIFOLD 96
6. 3. 2 AI HOSES 50
6. 3. 3 AI AIR FILTER 50
6. 3. 4 AI CHECKVALVES 84
6. 3. 5 AI BYPASS/DVRTR 50
6. 3. 6 AI GULP VALVES 0
6. 3. 7 AI PUMP/BELTS 50
6. 4. 1 EGR VALVES 75
6. 4. 2 EGR HOSES/SEALS 72
6. 4. 3 EGR THERMO VALVE 62
6. 4. 4 EGR SOLENOID VLV 27
6. 4. 5 EGR TEMP SWITCH 13
6. 4. 6 EGR SPEED/TRANS 11
6. 4. 7 EGR TIME DELAY 13
6. 4. 8 EGR VAC AMP 21
6. 4. 9 EGR VAC REDUCER 1
6. 4.10 EGR CARB SPACtR 11
6. 4.11 EGR bACKPRES SEN 4
6. 4.12 EGR CHECKVALVE 1
6. 5. 1 TCS VAC SOLENCID 31
6. 5. 2 TCS VAC HOSES 33
6. 5. 3 TCS TIME DELAY 21
6. 5. 4 TCS CEC VALVE 2
6. 5. 5 TCS THERMO VALVE 5
6. 5. 6 TCS TRANS SWITCH 33
6. 5. 7 TCS REVERSE RELY 0
6. 5. 8 TCS TEMP SWITCH 38
6. 6. 1 SCS VACUUM SCLEN 2
6. 6. I SCS VACUM LINE 2
6. 6. 3 SCS TIME DELAY 0
6. 6. 4 SCS SPEED SWITCH 2
6. 6. 5 SCS THERMO VALVE 1
SALES DATA
GARAGE WAREHOUSE
SALES SALES
SALES VOLUME FACTORS
OEM GARAGE WAREHOUSE
SALES SALES SALES
0
0
0
0
0
0
0
0
0
0
c
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
18460
0
0
0
0
8748
0
0
2636
0
716
5800
0
0
0
0
0
0
3000
0
0
0
0
5620
0
0
0
0
0
0
5300
0
0
0
0
0
0.0171
0.0061
0.0031
0.0062
0.0061
O.OC32
0.0032
O.C053
0.0032
O.C
O.G032
O.CC47
O.CC45
O.OC39
O.CC17
0.0008
O.OC07
O.CCC8
O.CC13
O.CC01
O.OC07
0.0003
0.0001
O.CC20
0.0021
O.C013
O.OC01
0.0003
0.0021
0.0
O.C024
O.CC01
O.C001
0.0
O.C001
0.0001
O.C
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
c.o
3.0
0.0
0.0
O.C
0.0
u.O
0.0
0.0
0.0
O.C
0.0
0.0
c.o
0.0
0.0
c.o
0.0
c.o
0.0
0.0
0.0
0.0
O.OC30
0.0
0.0
0.0
0.0
0.0014
0.0
0.0
0.0004
0.0
0.0001
O.OC09
0.0
0.0
0.0
0.0
0.0
0.0
0.0005
0.0
0.0
0.0
0.0
0.0009
0.0
0.0
0.0
0.0
0.0
0.0
0.0009
0.0
0.0
0.0
0.0
0.0
-------
Table 4-4. SALES VOLUME FACTORS (Continued)
I
<7>
CO
PART
CODE
6. 7.
6. 7.
6. 7.
6. 7.
6. 7.
6. 8.
6. 8.
6. 8.
6. 8.
6. 8.
6. 9.
6. 9.
6. 9.
6. 9.
6.10.
6.10.
6.10.
6.10.
6.10.
6.10.
6.10.
7. 1.
7. 2.
7. 3.
7. 3.
8. 1.
1
2
3
4
5
1
2
3
4
5
1
2
3
4
1
2
3
4
5
6
7
n
0
1
2
0
PART NAME
OSAC VAC ORIFICE
CSAC VAC HOStS
OSAC THERMO VALV
OSAC VAC BYPASS
OSAC TEMP SENSOR
ESC ELEC MODULE
ESC HOSES
ESC VAC VALVES
ESC TEMP SWITCH
ESC SPEED SWITCH
CAT BODY
CAT ACTIVE MEDIA
CAT INERTMEOIA
CAT SHELL
HEAT RISER
ELEC ASSIST CHKE
STAGED PULLDOWN
DECEL VALVE
DIST VACDECL VLV
DIST START SCLEN
THERMO VAC VALV
COOLING THERMST
ELECTRICAL SYSTM
HIGH PERF EXHAST
EXHAUST MANIFOLD
DISTR VACUUM VLV
OEM
SALES
12
12
a
5
5
5
4
4
4
7
0
0
0
0
60
29
6
4
1
2
20
101
100
9
173
0
SALES
GARAGE
SALES
0
0
0
c
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
16139
0
1000
46941
0
DATA
WAREHOUSE
SALES
0
0
0
0
0
0
0
0
0
0
0
0
0
0
6446
0
0
3024
0
0
20000
0
0
396
600
0
SALES VOLUME FACTORS
OEM GARAGE WAREHOUSE
SALES SALES SALES
O.QC08
0.0008
O.C
0.0003
O.C003
O.C003
O.CC03
0.0003
O.C003
0.0004
O.C
0.0
0.0
0.0
0.0038
O.CC18
0.0004
O.CCC3
O.CC01
0.0001
0.0013
O.CC64
O.C063
O.CC06
O.C109
O.C
G.O
0.0
0.0
0.0
G.O
0.0
0.0
0.0
0.0
0.0
O.C
0.0
0.0
0.0
c.o
0.0
0.0
0.0
0.0
0.0
0.0
0.0148
c.o
O.CJO9
O.C431
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0311
0.0
0.0
0.0005
0.0
0.0
0.0033
0.0
0.0
0.0001
0.0001
0.0
-------
• Sales or production volume of 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
recommended during the certification design
life.
Some component categories were assigned different
after-market sales volume factors than were used as OEM
factors. These components were either classed only as OEM
or after-market, or the after-market usage would have been
substantially different than OEM usage, i.e., certain
specialty equipment not intended for OEM replacement. The
following after-market sales volume factors were different
than the OEM sales volume:
• Idle mixture and timing adjustments were
deleted, i.e., assigned zero sales volume,
since they are not physical components subject
to after-market replacement.
• Carburetor rebuilding kits were assigned the
OEM carburetor sales volume factor.
• Specialty, i.e., performance, carburetors
were assigned 5 percent of the new carburetor
sales volume factor.
• Mechanical advance was assigned 5 percent of
the OEM distributor sales volume factor to
reflect specialty modifications to the centri-
fugal advance curve.
• CD electronic ignition retrofit systems were
assigned 5 percent of the OEM distributor
sales volume factor.
4-64
-------
0 Intake manifolds were assigned 5 percent of
the OEM engine sales volume factor.
• Turbochargers and superchargers were each
assigned 1 percent of the OEM engine sales
volume factor.
t Specialty cams, camshafts, headers, and
valves were assigned 5 percent of the OEM
sales volume factor.
• After-market catalyst systems were assigned
zero sales volume since they are expected to
remain an OEM supplied replacement component.
4.2.4.2 Garage Sales Volume Factors
These sales volume factors were based on sales
reported in the 1975 Service Job Analysis (Ref. 106). The
categories reflected general service actions and, with some
exceptions, did not report sales volumes by individual compo-
nent categories. For those component categories with reported
sales volume, the actual number in thousands was used.
Sales volume factors of most other categories were assigned
values of zero. However, some factors were assigned values
on the basis of engineering judgment and data from the
warehouse sales survey. These factors and the assumed
values are discussed below:
• Specialty, i.e., performance, carburetors were
assigned 5 percent of the new installed
carburetor sales.
• Individual carburetor components except jets
and carburetor kits were assigned 10 percent
of the overhauled carburetors.
t Condensers were assigned the same sales
volume factor as points, since these components
are generally replaced at the same time.
4-65
-------
t Caps, rotors, and coils were assigned 25 percent
of the total tune-up sales volume.
t Distributors and distributor components were
assigned 5 percent of total tune-up sales
volume.
• Replacement El trigger components were assigned
the sum of trigger wheel and pole piece
replacements.
t Spark plug replacements were assigned the sum
of new replacement and regapped plugs.
• Cams, and camshafts, were both assigned the sum
of new and reground camshafts.
0 Valve guides, seals, and exhaust valves were
assigned the sum of valve replacements and
valve grinding jobs.
• Rings were assigned the number of replacement
sets installed.
t Pistons were assigned 50 percent of the sum
of crankshafts, rod bearings and main bearings.
• Head gaskets were assigned the sum of con-
ditioned cylinder blocks and valve jobs.
• PCV filters were assigned 50 percent of the
air filter replacements.
• All other components were assigned sales
volume factors of zero.
4.2.4.3 Warehouse Sales Volume Factors
These sales volume factors were based on a limited
survey of 25 warehouse distributors. Five responses were
received which represented approximately 1 percent of the
membership of the Automotive Warehouse Distributors Associ-
ation. In addition, the sales of OEM Products, Inc., a
distributor of emission control components was added to the
warehouse sales survey results. OEM Products, Inc., claims
4-66
-------
to distribute components to 1 percent of the warehouse
distributors. It was, therefore, felt that a direct sum of
the six surveys was as accurate as any type of weighted sum.
The results of the survey were used directly for
all components explicitly listed. Some component categories
were not included, however. The following criteria was used
to assign nonzero sales volume factors to these components.
• Specialty, i.e., performance, carburetors
were assigned 5 percent of the new replacement
carburetor sales volume.
• Pumps for fuel injection systems were assigned
1 percent of total fuel pump sales.
• All vacuum solenoid sales were assigned to
TCS solenoid category.
t Air injection pump sales were assigned to the
AI pump and belt category.
• All other components were assigned zero sales
volume.
4.3 RANKINGS OF EMISSION-CRITICAL AFTER-MARKET COMPONENTS
The rankings of emission-critical after-market
components are shown in Tables 4-5 through 4-7. These
rankings are abstracted from the tables shown in Appendix A
which contain detailed rankings for the six combinations of
model-year group and sales volume data source. Tables 4-5
through 4-7 present independent rank-ordered lists for HC,
including evaporative emissions, CO, NO , smoke, and a
/\
composite ranking based on the absolute value of the criti-
cality indices regardless of pollutant.
In general, the order of the rankings depended on
model-year group and sales volume although the same components
generally ranked in the top 25. Most components were critical
4-67
-------
Table 4-5. AFTER-MARKET PART CRITICALITY RANKING
(Automotive Parts Study - EPA Contract 68-01-1957)
WAREHOUSE SALES VOLUME AND EARLY MODEL EMISSION FACTORS
HCT
CO
NOT
(Diesel;
COMPOSITE
I
O1
00
Spark Plugs
Ignition Wires
Rebuilding Kits
Rebuilt Carburetor
Rotor
Cap
Choke Mechanism
New Carburetor
Valve Lifter/Spring
Points
Valve Seals
Exhaust Valves
Specialty Carburetor
Coil
Condenser
PCV Valve
Air Cleaner Element
Spark Delay Valve
Fuel Filter
Distributor Drive
EVAP Fresh Air
AI Hoses
Valve Guides
Head Gaskets
Piston Rings
Rebuilding Kits
Choke Mechanism
Rebuilt Carburetor
New Carburetor
Air Cleaner Element
Valve Lifter/Spring
PCV Valve
Valve Seals
Exhaust Valves
Specialty Carburetor
Vacuum Break Valve
PCV Freshair Filter
Idle Stop Solenoid
Throttle Dashpot
Decel Valve
AI Hoses
Valve Guides
Head Gaskets
Piston Rings
Camshafts
Vacuum Advance
AI Pump/Belts
Intake Manifold
Mechanical Advance
Valve Cam Lobes
Thermal Vac Valve
Spark Delay Valve
EGR Valves
Rebuilt Carburetor
Specialty Carburetor
New Carburetor
EGR Vacuum Amplifier
TCS Vacuum Solenoid
TCS Temp Switch
Mechanical Advance
Exhaust Manifold
High Perf Exhaust
Valve Lifter/Spring
Valve Seals
Exhaust Valves
Air Cleaner Element
FI Throttle Valve
Valve Guides
Head Gaskets
Piston Rings
Camshafts
Valve Cam Lobes
FI Hi Pres Pump
Spark Plugs
Rebuilding Kits
Ignition Wires
Choke Mechanism
Rebuilt Carburetor
New Carburetor
Rotor
Cap
Air Cleaner Element
Valve Lifter/Springs
Thermal Vacuum Valve
PCV Valve
Spark Delay Valve
Points
EGR Valves
Valve Seals
Exhaust Valves
Specialty Carburetor
Vacuum Break Valves
PCV Fresh Air Filter
Coil
Idle Stop Solenoid
Condenser
EGR Vacuum Amplifier
Throttle Dashpot
-------
Table 4-6. AFTER-MARKET PART CRITICALITY RANKING
(Automotive Parts Study - EPA Contract No. 68-01-1957)
GARAGE SALES VOLUME AND EARLY MODEL EMISSION FACTORS
HC
NO"
SMOKE (Diesel)
COMPOSITE
Spark Plugs
Ignition Wires
Cap
Rotor
Rebuilding Kits
Float and Valve
Points
Valve Lifter/Springs
Exhaust Valves
Rebuilt Carburetor
Valve Seals
Condenser
Mag/Opt Triggers
El Control Circuit
New Carburetor
PCV Valve
Piston Rings
Air Cleaner Element
Exhaust Manifold
Fuel Filter
Valve Guides
Specialty Carburetor
Head Gaskets
Valve Cam Lobes
Camshafts
Rebuilding Kits
Float and Valve
Air Cleaner Element
PCV Valve
Valve Lifter/Spring
Rebuilt Carburetor
Exhaust Valves
Valve Seals
New Carburetor
Piston Rings
Exhaust Manifold
Valve Guides
Specialty Carburetor
Head Gasket
Valve Cam Lobes
Camshafts
High Perf Exhaust
FI Hi Pres Pump
Idle Stop Solenoid
Throttle Dashpot
Throttle Positioner
Metering Jets
Metering Rods
Vacuum Break Valve
Choke Mechanism
Exhaust Manifold
Rebuilt Carburetor
Specialty Carburetor
New Carburetor
High Perf Exhaust
Valve Lifter/Spring
Exhaust Valves
Air Cleaner Element
Valve Seals
Piston Rings
Valve Guides
Head Gaskets
Valve Cam Lobes
Camshafts
FI Hi Pres Pump
Spark Plugs
Ignition Wires
Rebuilding Kits
Float and Valve
Cap
Rotor
Air Cleaner Element
PCV Valve
Points
Valve Lifter/Springs
Rebuilt Carburetor
Exhaust Valves
Valve Seals
New Carburetor
Condenser
Mag/Opt Triggers
El Control Circuit
Piston Rings
Exhaust Manifold
Fuel Filter
Valve Guides
Specialty Carburetor
Head Gaskets
Valve Cam Lobes
Camshafts
-------
Table 4-7. AFTER-MARKET PART CRITICALITY RANKING
(Automotive Parts Study - EPA Contract 68-01-1957)
OEM SALES VOLUME AND LATE MODEL EMISSION FACTORS
HC
NOT
SMOKE. (Diesel)
COMPOSITE
Spark Plugs
Ignition Wires
Rebuilding Kits
Float and Valve
Choke Mechanism
Power Valves
EVAP Canister
Rebuilt Carburetor
Heat Riser
PCV Valve
Rotor
Cap
New Carburetor
Vacuum Break Valve
TAG Vacuum Motor
TAG Vacuum Hoses
PCV Fresh/Air Filter
PCV Hoses
EVAP Hoses
Valve Lifter/Springs
Idle Stop Solenoid
EVAP Fresh Air Filter
TAC Shroud
TAG Thermostat
AI Hoses
Rebuilding Kits
Float and Valve
Choke Mechanism
Power Valves
Rebuilt Carburetor
New Carburetor
Accelerator Pump
Metering Rods
Air Cleaner Element
Metering Jets
PCV Valve
Spark Plugs
Vacuum Break Valve
AI Hoses
AI Pump/Belts
PCV Fresh Air Filter
Specialty Carburetor
Vacuum Advance
AI Bypass/Diverter
Valve Lifter/Springs
Idle Stop Solenoid
Ignition Wires
Valve Seals
Exhaust Valves
AI Manifold
EGR Valves
EGR Thermal Valve
Spark Delay Valve
EGR Vacuum Amplifier
Thermal Vacuum Valve
EGR Hoses/Seals
TCS Temp Switch
TCS Trans Switch
TCS Vacuum Solenoid
EGR Solenoid Valve
Rebuilt Carburetor
TCS Time Delay
OSAC Vacuum Orifice
Specialty Carburetor
EGR Carb Spacer
TCS Thermal Valve
New Carburetor
EGR Backpres Sensor
EGR Temp Switch
EGR Time Delay
EGR Speed/Trans Sen
OSAC Vacuum Bypass
ESC Speed Switch
ESC Elec Module
Exhaust Manifold
Valve Lifter/Springs
Valve Seals
Exhaust Valves
Air Cleaner Element
MFI Valves
Valve Guides
Piston Rings
Head Gaskets
FI Throttle Valve
Valve Cam Lobes
FI Pres Sens/Reg
Supercharger
PCV Oil Separator
Camshafts
Turbocharger
FI Dist Manifold
FI Hi Pres Pump
Spark Plugs
Ignition Wires
Rebuilding Kits
Float and Valve
Choke Mechanism
Power Valves
Valve Lifter/Springs
Rebuilt Carburetor
EGR Valves
Valve Seals
Exhaust Valves
New Carburetor
Accelerator Pumps
EVAP Canister
Heat Riser
Metering Rods
Air Cleaner Element
EGR Thermal Vac Valve
Metering Jets
PCV Valve
Rotor
Cap
Vacuum Break Valve
TAC Vacuum Motor
TAC Vacuum Hoses
-------
to more than one pollutant, although not necessarily to the
same degree. Critical after-market components for HC and CO
typically included the following:
• Primary ignition components such as points,
condenser, and coil.
t Secondary ignition components such as spark
plugs and wires, and distributor caps and
rotors.
t Carburetion components such as chokes, power
valves, metering rods, floats and needle
valves.
• Induction components such as air filter
*,
elements.
• After-market carburetors and carburetor
rebuilding kits.
t Mechanical components such as piston rings
and valve train components.
Emissions of NO were dependent on the performance
X
of NO control systems, including the EGR valve and control
/\
components, and carburetion or vacuum control components
which can affect vacuum signals for EGR valve operation or
timing advance.
Smoke emissions were related to 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 if defective or
not-OEM equivalent. 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
4-71
-------
Table 4-8. AFTER-MARKET COMPONENTS WHICH CAN CAUSE
AN EMISSION FAILURE IF IMPROPERLY INSTALLED OR DEFECTIVE
PART OR COMPONENT
Carburetor System
New Carburetor
Rebuilt Carburetors
Idle Stop Solenoid
Throttle Dashpot
Throttle Positioner
Metering Jets
Metering Rods
Vacuum Break Valves
Choke Mechanism
Power Valves
Float and Valve
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 Wires
Coil - Inductive
Ballast Resistor
Spark Delay Valve
Air Induction System
Thermos tatical ly-Controlled
Air Inlet
Vacuum Motor and Hoses
Air Cleaner Element
Turbochargers and Superchargers
Intake Manifolds
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
CO
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
NOX
X
X
Smoke
X
X
4-72
-------
Table 4-8. AFTER-MARKET COMPONENTS WHICH CAN CAUSE
AN EMISSION FAILURE IF IMPROPERLY
INSTALLED OR DEFECTIVE (Cont'd)
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
Engine System
Valve Lifters and Springs
Cams
Valves, Guides and Seats
Seals
Rings
Gaskets
Camshafts
Emission Control System*
PCV Valve
PCV Hoses
PCV Fresh Air Filter
AI Distribution Manifold
AI Hoses
AI Inlet Filter
AI Check Valves
AI Bypass/Diverter 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
CO
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
*These components are not all available in the after-market at
this time but may become available in the future.
4-73
-------
Table 4-8. AFTER-MARKET COMPONENTS WHICH CAN CAUSE
AN EMISSION FAILURE IF IMPROPERLY
INSTALLED OR DEFECTIVE (Cont'd)
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
Heat Riser
Decel Valve
Distributor Vacuum Deceleration Valve
Distributor Starting Solenoid
Thermal Vacuum Valve
EMISSIONS FAILURE
HC
X
X
X
X
X
CO
X
X
X
X
X
X
X
N0x
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
4-74
-------
can be seen from Table 4-8, most of the components would
result in a failure of one or more standards if defective.
As with the OEM components, the criticality rankings
of after-market components were sensitive to changes in the
input parameters. The criticality rankings were generally
dependent on which sales volume factors were used. The
garage sales rankings emphasized ignition, carburetion, and
mechanical component criticality- The OEM sales ranking
included more specialized emission control components. The
warehouse sales rankings reflected primarily ignition and
carburetion components. In all rankings, however, the
lowest ranked components were several orders of magnitude
lower in criticality than the highest ranked components and
the top 5 to 10 components were generally the same although
their order may have been different.
The rankings of critical after-market components
presented above may be compared with a ranking developed
from factors estimated by the Automative Liaison Council's
Automotive Products Emissions Committee (ALC-APEC) which is
shown in Table 4-9. The ALC-APEC rankings do not include
all individual components considered above and consider
failures resulting from defects rather than misapplication
or improper installation. Except for catalysts which were
not included, the ALC-APEC rankings were generally similar
to the after-market part criticality rankings developed
above.
4-75
-------
Table 4-9. AUTOMOTIVE PART CRITICALITY RANKING
(Automotive Liaison Council-Automotive Products Emissions Committee)
HC
CO
NO.
COMPOSITE
Catalyst
Spark Plugs
Points
PCV System
Air Cleaner
EGR System
Carburetor
EVAP System
Thermal Reactor
Air Injection
Emission Control Component
Distributor Advance
Exhaust Valves
Thermostatic Air Cleaner
Exhaust System
Distributor
Catalyst
Air Cleaner
Spark Plugs
Points
Air Injection
Thermal Reactor
Carburetor
PCV System
EGR System
Emission Control Component
Distributor Advance
Thermostatic Air Cleaner
Exhaust Valves
Exhaust System
EVAP System
Distributor
EGR System
Catalyst
Spark Plugs
Distributor Advance
Emission Control Components
Air Cleaner
Carburetor
Points
PCV System
Thermostatic Air Cleaner
Exhaust System
Air Injection
Thermal Reactor
EVAP System
Distributor
Exhaust Valves
Catalyst
Spark Plugs
Carburetor
Air Cleaner
Air Injection
Thermal Reactor
EGR System
Emission Control Component
Points
Distributor Advance
PCV System
Thermostatic Air Cleaner
Distributor
Exhaust Valves
EVAP System
Exhaust System
-------
Section 5
CRITICAL PARAMETERS
This section discusses the critical parameters of
the most emission-critical after-market components. Critical
parameters were defined to include factors or specifications
of the part, component, or system which directly affect the
emissions of one or more pollutants, or which indirectly
affect emissions by affecting the operation of other critical
components; i.e., vacuum control valves. The critical
factors or specifications were generally classified as one
or more of the following:
• Dimensions.
• Materials.
• Flow curve (flow volume or rate as a function
of pressure or vacuum signals).
• Movement characteristics (length, direction,
and speed of travel or actuation signal).
• Electrical properties (resistance, capacitance,
inductance, voltage, current, voltage rise
time and dielectric strength).
• Thermodynamic properties (conductivity,
operating temperature, thermal expansion).
Although discussed individually, these character!'sts are
generally interrelated; i.e., thermal conductivity, depends
on materials while flow curves depend on dimensions.
5-1
-------
Critical parameters were determined for the five
most critical after-market components for each pollutant.
The five most critical components were selected from all
three criticality rankings shown in Tables 4-5, 4-6, and
4-7 in order to encompass as many of the components as
possible. Table 5-1 summarizes the components selected and
their critical parameters. Each of these components is
discussed below.
5.1 CARBURETION SYSTEM COMPONENTS
The following carburetion system components were
among the five most critical in at least one ranking.
• Carburetors
New replacement
Rebuilt replacement
Speciality (performance)
• Carburetor Components
Rebuilding kit
Choke thermostat
Float and needle valve
Power valve
5.1.1 Carburetors
All three subgroups of assembled carburetors have
the same critical performance parameters. These are related
to the flow curve of the carburetor and the air fuel ratio
as a function of air flow rate and vacuum. The fuel metering
rate is controlled by the venturi vacuum at the point were
fuel is admitted. Power enrichment either by vacuum diaphragm
operated valves or by metering rod movement should occur
under similar speed and load conditions for the after-market
carburetor as for the OEM carburetor.
5-2
-------
Table 5-1. SUMMARY OF CRITICAL PARAMETERS OF EMISSION-CRITICAL AFTER-MARKET PARTS
SYSTEM/COMPONENT
Carbureti on System
Rebuilding Kits
Rebuilt Carburetors
New Carburetors
Specialty Carburetors
Choke Thermostats
Float and Valves
Power Valves
Ignition System
Spark Plugs
Wires
Rotors
Caps
Induction System
Air Cleaner Elements
Mechanical System
Exhaust Manifolds
Headers
Valve Lifters/Springs
Exhaust Valves
Valve Seals
Piston Rings
Fuel Injection System
MFI Valves
FI Throttle Valves
Emission Control System
EGR Valves
Thermal Vacuum Valves
EGR Vacuum Amplifiers
Spark Delay Valves
CRITICAL PARAMETERS
Dimensions
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Materials
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Flow Curve
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Movement
X
X
X
X
X
X
X
X
X
X
Electrical
X
X
X
X
Thermodynamic
X
X
X
X
X
X
X
X
X
X
-------
The venturi vacuum depression and, therefore, the
fuel metering rate and air fuel ratio are controlled by the
air velocity through the carburetor. This is dependent on
the dimensions (i.e., cross sectional area) of the carburetor
throats as well as the physical construction of the fuel jet
orifices, vacuum required for diaphragm actuation, and
mechanical adjustments. This requires that the carburetor's
design flow range be compatible with that of the engine, and
that components of the carburetor be generally equivalent in
dimension, adjustment, and operation as the OEM carburetor.
In addition to the fuel metering and air fuel
ratio characteristics, the after-market carburetor must have
equivalent vacuum signals at the E6R, venturi, and or spark
advance ports as the OEM carburetor in order to produce OEM
equivalent vacuum advance and EGR operation. Differences in
these characteristics can significantly affect emissions
performance, particularly of NO .
A
5.1.2 Carburetor Components
Critical parameters of carburetor components vary
by component. However, the dimensions of all the selected
components are critical to their proper function and, conse-
quently, their emissions performance. In establishing their
critical performance parameters, it was assumed that each
would be individually installed as an after-market part in
an OEM carburetor.
5.1.2.1 Rebuilding Kit
In addition to dimensional equivalence, several
components require similar materials as the OEM components;
or materials which have similar properties. In particular,
componets such as gaskets and vacuum diaphragms which are
distributed in carburetor rebuilding kits should be made
5-4
-------
from similar materials as the OEM components to ensure that
compression, sealing, and response or resistance to vacuum,
liquids (gasoline, water, or oil), vapors (fuel vapors,
smoke), and environmental conditions (temperature) are
equivalent to the OEM components.
5.1.2.2 Choke Thermostat
The choke thermostat depends on dimensional equiva-
lence to the OEM part and an equivalent coefficient of
thermal expansion to ensure that the same rotation of the
choke plate occurs over a specified temperature range.
Thermodynamic properties of the thermostat are governed by
the materials used to make the coil spring.
5.1.2.3 Float and Needle Valve
The float and needle valve are frequently replaced
as a set. Both of these components must have dimensional
equivalence to ensure that the same fuel height is maintained
as with the OEM components. This includes installing the
needle valve, valve seat, and float arm in identical locations
of the float chamber as with the OEM components.
5.1.2.4 Power Valve
After-market power valves generally involve replace-
ment of vacuum diaphragms. The replacement diaphragm and
return springs, if replaced, should result in the same
carburetor metering as the OEM components. This requires
that the components have similar elasticity and spring
coefficients so that the valve's response to carburetor
vacuum signals is the same as for the OEM power valve. The
critical parameters for power valve are, therefore, dimensions,
materials, and flow curve.
5-5
-------
5.2 IGNITION SYSTEM COMPONENTS
Four components of the ignition system ranked
among the five most critical components:
t Spark plugs
• Mires
• Rotors
• Caps
5.2.1 Spark Plugs
Spark plugs were the most critical after-market
component for HC emissions in all the rankings. This is due
to the high sales volume of spark plugs and the substantial
effect a plug failure has on HC emissions in particular.
The spark plug is critically dependent on gap length and
relative position in the cylinder. These two parameters are
determined by dimensional equivalence of an after-market
spark plug to the OEM plug.
In general, the durability of spark plugs depends
on how long the gap remains within the allowable tolerance.
Changes in gap length are caused either by plug fouling or
electrical erosion of the electrode. In both cases, the
plug degrades until the required firing voltage is higher
than the available voltage, or the firing time is too short
to ignite the charge. The rate of plug fouling is, in turn,
controlled by the operating temperature of the plug which
depends on materials of construction, design heat range, and
installation technique.
5.2.2 Wires
Wires were critically related to HC emissions in
all rankings. The performance of ignition wires depends on
5-6
-------
their ability to deliver the required firing voltage to the
spark plug. The important properties of wires are, therefore,
electrical properties such as conductivity, capacitance, and
the dielectric strength of the insulation around the wire
and which covers the connectors at each end. These properties
are controlled by selection of the materials used for the
wires and, to a lesser extent, by the dimensions (length and
diameter) of the conductor and insulation.
Wires typically perform satisfactorily after
installation regardless of quality. The durability of the
wire, however, depends on the materials and the ability of
the wire to resist heat stress and vibration.
5.2.3 Rotors
Distributor rotors must have dimensional equivalence
to the OEM rotor. This is required to ensure proper electrode
registration between the rotor terminals and the terminals
on the cap. In addition, the configuration and materials of
construction must prevent arcing of the high voltage through
or across the body of the rotor to ground represented by the
distributor shaft and body. Failure to maintain proper
dimensions, registration and arc resistance will result in
shorter useful life of the rotor and/or cap and changes in
the available firing voltages, spark initiation or duration.
5.2.4 Caps
After-market distributor caps must also be dimension-
ally equivalent to the electrodes and terminals of the OEM
cap. Overall dimensions and configuration may be different,
however, provided that electrical properties of conductivity
and arc resistance are equivalent to the OEM cap.
5-7
-------
5.3 AIR INDUCTION SYSTEM COMPONENTS
The only air induction system component which
ranked among the five most critical components was the air
cleaner element. The critical parameter of the air cleaner
is the flow curve. The flow curve is dependent on both the
cross sectional area and the pressure drop across the filter
media. Factors which affect these parameters include the
element's external dimensions and configuration, and the
depth, density, and nature of the filtering media. Differences
in these factors, however, can result in the same flow
curve.
5.4 MECHANICAL SYSTEM COMPONENTS
Six mechanical components ranked among the five
most critical components. Two components (exhaust manifolds
and headers) ranked high in NO emission-criticality only
/\
because there were only five NO emissions-related components
/\
with nonzero garage sales volume factors. The other four
components were internal engine components (valve lifters/
springs, exhaust valves, valve seals, and piston rings).
5.4.1 Exhaust Manifolds and Headers
Exhaust manifolds and headers are generally associ-
ated with OEM replacement and performance modifications,
respectively. Both components, however, involve flow curves
as critical parameters. The exhaust back pressure at the
cylinder exhaust valves as a function of exhaust flow rate.
Manifolds sold as OEM replacement must have dimensional and
possibly material equivalence to the OEM manifold. The
headers, however, generally are not equivalent to OEM manifold
in any respect.
5-8
-------
5.4.2 Internal Engine Components
The valve train components and piston rings requires
dimensional equivalence to the OEM components. To ensure
equivalent durability, similar material and fabrication
techniques are also necessary. Failure to maintain equivalent
dimensions and physical properties of valve train components
may result in changes in timing, duration, and rate of valve
opening. Non-tfEM equivalent piston rings may result in low
cylinder compression, excessive oil burning or plug fouling,
or excessive crankcase blowby.
5.5 FUEL INJECTION SYSTEM
Two fuel injection components ranked high in smoke
emission-criticality; injection valves and throttle valves.
Both of these components require dimensional equivalence to
the OEM component in order to be installed in a diesel
engine. Both of the components also require equivalent flow
curves to ensure that the same rate of fueling occurs for
given engine speed and load.
5.6 EMISSION CONTROL SYSTEM COMPONENTS
Four emission control components were among the
five most NO emission-critical components; one of the
components is the EGR valve. Three of the components
modulate vacuum signals actuating EGR operation or timing
advance. The components were the following:
• EGR valve
• Thermal vacuum value
t EGR vacuum amplifier
• Spark delay valve
5-9
-------
5.6.1 EGR Valve
The EGR valve opens a passage between the intake
and exhaust manifolds. The valve is actuated by a vacuum
diaphragm and return spring. The critical parameter of the
EGR valve is the flow curve of recirculated exhaust gas as a
function of carburetor flow rate and venturi vacuum. Non-
OEM equivalent vacuum diaphragm or spring operation will
result in different exhaust gas recirculation rate and
may affect either engine performance NO emissions.
y\
5.6.2 Thermal Vacuum Valve
The thermal vacuum valve opens or closes vacuum
ports in response to coolant temperature. The performance
of the valve depends on the thermal conductivity and heat
capacity of the soft solder plug in the base of the valve,
and the ball valves and springs controlling the vacuum
signal. Equivalent performance is generally provided by
dimensional and material equivalence of the OEM and after-
market components.
5.6.3 EGR Vacuum Amplifier
The EGR vacuum amplifier is a vacuum switch which
regulates a manifold vacuum signal in response to weaker
venturi vacuum signals. The operation of the EGR valve
depends on the diaphragm and spring tension of the vacuum
amplifier switch. These parameters are regulated by the
dimensions and material of the component.
5.6.4 Spark Delay Valve
The spark delay valve is an in-line air bleed
which restricts airflow in one direction. The valve typically
5-10
-------
consists of a restricted orifice and check valve. The
critical parameter of the spark delay valve is the porosity
or leak down rate in both flow directions. These factors
are generally governed by materials and dimensions, however,
alternative designs can yield the same flow curve.
5-11
-------
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 after-market components selected for testing are
discussed in paragraph 6.1. The test protocol recommended
for the 25 components is discussed in paragraph 6.2.
6.1 SELECTION OF COMPONENTS
The after-market components selected for testing
primarily include 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 involving
after-market component installation on catalyst-equipped
vehicles were generally not reported. Some components
recommended for testing may be included as OEM components in
on-going or planned restorative maintenance and characteriza-
tion programs and, therefore, may be subsequently deleted.
Components have been chosen from those which
appear on either Table 4-5 or 4-7 since these rankings
provided the best estimate of current and future criticality
Table 4-5 was based on the pre-catalyst emission increase
factors and warehouse distributor sales volumes. Table 4-7
6-1
-------
was based on the OEM sales volume factors and post-1975
emission increase factors.
Table 6-1 summarizes the components recommended
for testing. Several components have more than one basic
operating design. One each of these multiple configurations
should be tested where appropriate.
6.1.1 Carburetion System Components
Carburetion components are critical to both HC and
CO emissions. Carburetor replacement may also be critical
to NO if EGR or timing advance vacuum signals differ from
A
the OEM carburetor. The following carburetion components
were recommended for testing on both air injection and
nonair injection-equipped vehicles:
t New carburetors
t Rebuilt carburetors
t Specialty carburetors
t Choke thermostats
• Floats and valves
• Power valves
t Metering jets
• Dashpots
• Carburetor rebuilding kits
The other major carburetor components (gaskets, accelerator
pumps, throttle positioners, and idle adjustments) are not
recommended for testing due to their low criticality as
after-market components or because they have been recommended
for testing as OEM components.
At least four representative units from each
recommended component category should be tested on each
selected vehicle. Each component would be installed in
accordance with the vehicle and/or component manufacturer's
6-2
-------
Table 6-1. AFTER-MARKET COMPONENTS RECOMMENDED FOR TESTING
COMPONENT
TEST CONDITIONS
Carburetion System
New Carburetor
Rebuilt Carburetor
Specialty Carburetor
Carburetor Rebuilding Kit
Choke Thermostat
Float and Valve
Metering Jet
Dashpot
Ignition System
Spark Plugs
Ignition Wires
Points
Condenser
Coil
Distributor Cap
Distributor Rotor
Vacuum Advance Unit
Retrofit CD Electronic Ignition
Optical/Magnetic Retrofit
El Distributor System
Replacement Distributor
Engine System
Valve Lifters/Springs
Intake Manifold/Headers
Emission Control System
PCV Valve
Decel Valve
Spark Delay Valve
Thermal Vacuum Valve
OEM •
OEM -
OEM -
OEM •
OEM •
OEM •
Lean
OEM •
OEM
OEM
OEM
OEM
OEM
OEM
OEM
OEM
OEM
OEM
OEM
OEM
OEM
OEM
OEM
OEM
OEM
After-market
After-market
After-market
Rebuilding Kit
After-market
After-market
• OEM - Rich
After-market
After-
After-
After-
After-
After-
After-
After-
After-
After-
market
market
market
market
market
market
market
market
market
After-market
After-market
After-market
After-market
After-market
After-market
After-market
After-market
6-3
-------
instructions. Prior to installing each component, the test
vehicle would receive a baseline test with all engine,
ignition and carburetion components inspected and set to
specification. The test of the after-market component would
then provide a measure of the emissions resulting from a
direct replacement of the OEM component with the recommended
after-market component.
OEM metering jets may be replaced with nonequiva-
lent after-market jets. The OEM jet may be replaced with a
larger jet in order to improve driveability and performance.
Although unlikely, it is also possible that the OEM jet
would be replaced by a smaller jet to improve fuel economy.
Therefore, four jet sizes are recommended for each vehicle
selected for testing: OEM supplied jet, two larger jet
sizes (0.010" and 0.020"), and one smaller jet size (0.005").
This range of metering jets should include the probable range
of jet size changes.
The emissions performance of carburetor rebuilding
kits are highly dependent on the thoroughness and competence
of the mechanic performing the repair. In order to minimize
the chance of error in rebuilding the carburetor, each test
vehicle would be sent to the same reputable independent
service garage. The mechanics would be aware that a study
of carburetor rebuilding practices was being performed.
Representative carburetors from each major carburetor
manufacturer should be included.
6.1.2 Ignition System Components
Ignition components are critically related to HC
and CO emissions. Some components may also affect NO emis-
A
sions. The following after-market ignition system components
are recommended for testing on both air injection and nonair
injection-equipped vehicles:
6-4
-------
• Spark plugs
• Ignition wires
• Points
• Condenser
t Coil
• Distributor caps
• Distributor rotors
• Vacuum advance units
• Electronic ignition (CD) retrofit systems
t Optical/magnetic retrofit El systems
• Replacement distributor
All of the above components are direct replacements
to OEM components. Therefore, each selected vehicle would
be tested with the OEM component installed and all ignition
and carburetion components set to manfacturers. The after-
market component would then be installed and all ignition
and carburetion component specifications rechecked and
reset, if necessary, to specification. Several after-market
components representative of each category should be tested.
6.1.3 Air Induction System
No after-market air induction components are
recommended for testing since they ranked low in emissions
criticality.
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.
6-5
-------
6.1.5 Mechanical Components
Two after-market engine components are recommended
for testing: replacement valve lifters and springs, and a
combination of specialty intake manifold and exhaust headers.
Valve lifters and springs ranked relatively high in critical-
ity due to high after-market sales volume. These components,
however, are usually not replaced during the emissions
warranty period. Two engines are recommended to be tested
with the OEM valve components installed and then with the
replacement after-market components installed.
One representative combination of specialty intake
manifold and exhaust headers is recommended for testing.
Although these components rank relatively low in emissions
criticality, they do represent typical performance modifica-
tions which can be expected on post-1975 model-year vehicles.
6.1.6 Emission Control Components
The following emission control components are
recommended for testing due to their expected impact on
emissions and availability in the after-market. Although
they are generally considered to be OEM distributed compo-
nents, after-market sources do exist.
• PCV valve
t Decel valve
• Spark delay valve
t Thermal vacuum valve
The selected vehicles would be tested with OEM
components and then with the recommended replacement component
6-6
-------
installed. Several different sources of each component
should be used if available.
6.2 TEST PROTOCOL
The after-market components selected for testing
would all be subjected to the following general test protocol
t Select representative test vehicles.
t Set all components to nominal specifications.
• Precondition test vehicle.
• Perform baseline tests with OEM components.
• Replace OEM component with after-market
components.
• Precondition test vehicle.
t Perform tests with after-market components.
• Perform restorative maintenance.
• Precondition test vehicle.
• Perform baseline test.
• 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:
6-7
-------
• Pelleted catalyst with air
• Pelleted catalyst without air
• Monolith catalyst with air
• Monolith catalyst without air
Testing is not recommended on pre-1975 model-year
or noncatalyst-equipped vehicles since they represent small
and decreasing fractions of the vehicle population. In
addition, the majority of existing data on after-market
equipment is based on pre-catalyst vehicles.
6.2.2 Precondi tioning
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 both to the baseline and after-market
test. Preconditioning 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
wi th 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. Carburetor or mechanical component
6-8
-------
replacements would be performed by reputable independent
garages under contractor supervision.
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
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 carburetion components and those compo-
nents 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 omission
by the short test, the following two short tests are
recommended:
• 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
6-9
-------
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.
The components listed below are recommended for
testing using the short tests only. These components are
expected to have significant affect on hot running emissions
in addition to cold start emissions 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
followi ng:
• Carburetion System
Float and valve
Power valve
Metering jet
Dashpot
• Ignition System
Spark plugs
Wi res
Cap
Rotor
Points
Coil
Condenser
Vacuum advance
Electronic ignition systems
Replacement distributors
6-10
-------
• Engine Mechanical System
Valve lifters and springs
Intake manifold/headers
• Emission Control System
PCV valve
Spark delay valve
E6R valve
Thermal vacuum valve
6.2.5.2 FTP Tests
Several carburetor 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:
t Choke
t Specialty carburetor
• New replacement carburetor
• Rebuilt carburetor
• Carburetor rebuilding kit
• PCV valve
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 (4) except for
the cold-start driving schedule, accumulated mileage, and
calibrations. The Key Mode test should be performed using
6-11
-------
NDIR analyzers for HC, CO, and NO emissions and the appro-
/\
priate 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.
6-12
-------
REFERENCES
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R-l
-------
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R-2
-------
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37. McWhannel , D.C., "Performance and Emission Characteris-
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39. CassJdy, J.F., "Electronic Closed Loop Controls for the
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40. Mullins, P.J., "Low-Cost Fuel Injection," Automotive
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41. Ganly, J.T., and G.S. Springer, "Physical and Chemical
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April , 1974.
42. Sweeney, M.P. and M.L. Brubacker, "Exhaust Hydrocarbon
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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 Ingnition 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, 0. 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
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Requirements of the 1970 Clean Air Amendments," PB-224
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82. "NAS Report on Technological Feasibility of 1975 - 76
Motor Vehicle Emission Standards. Evaluation of Catalyst
as Automotive Exhaust Treatment Devices," National
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83. Gomph, Henry L., "Evaluation of GM 1976 Prototype
Vehicles, A Catalytic Exhaust Manifold Systems," PB-218
686/4, June, 1972.
R-6
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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,
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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
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PB-190 264, March, 1970.
91. "Study of Catalytic Control of Exhaust Emissions for
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Catalytic Converters," Preliminary Report, Project M-
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96. Panzer, J., "Idle Emissions Testing: Some Effects of
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January, 1974.
R-7
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98. "The Effect of Ignition Timing Modifications on Emissions
and Fuel Economy," EPA-ECTD Report #76-4 AW, October,
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April 1975 and April 1976.
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Chicago, 1976.
107. "Effect of Automotive Parts on Vehicle and Engine
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Conversion," Report No. VE-76-49, California Air Resources
Board, July 30, 1976, revised November 1, 1976.
R-8
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Appendix A
CRITICALITY INDEX RANKINGS
-------
PART
CODE
2. 5. 0
2. 6. 0
1. 3. 8
5. 1. 1
5. 1. 4
5. 1. 5
1. 3. 9
1. 3. 4
1. 3. 6
6. 2. 1
1. 1. 2
2. 3. 2
2. 3. 1
1. 1. 1
6. 1. 2
6. 2. 2
2. 1. 0
6. 2. 3
2. 7. 0
2. 9. 0
5. 1. 3
5. 2. 0
6. 2. 6
6. 2. 4
2. 3. 5
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
CRITICALITY INDEX RANKING - OEM SALES VOLUME
PRINCIPAL RANKING - HC
EARLY MODEL
PART
NAME
SPARK PLUGS
IGNITION WIRES
REBUILDING KITS
VALVE LIFTER/SPR
VALVE SEALS
EXHAUST VALVES
FLOAT AND VALVE
CHCKE MECHANISM
POWER VALVES
EVAP CANISTER
REBUILT CARB
ROTOR
CAP
NEW CARB
PCV HOSES
EVAP HOSES
POINTS
EVAP FRSH AIR
COIL
BALLAST RESISTOR
VALVE GUIDES
PISTON RINGS
FUEL TANK/CAP
EVAP VPRLIG SEP
DISTRIBUTOR DRIV
RANK
1
Z
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
ML
CI
0.189E+00
0.677E-01
0.786E-02
0.709E-02
0.411E-02
0.411E-02
0.337E-02
0.334E-02
0.334E-02
0.318E-02
0.290E-02
0.187E-02
0.185E-02
0.174E-02
0.107E-02
0.107E-02
0.728E-03
0.569E-03
0.562E-03
0.562E-03
0.411E-03
0.411E-03
0.371E-03
0.367E-03
0.312E-03
RANK
67
68
1
5
7
8
2
3
4
88
6
63
62
9
87
89
60
90
69
71
18
19
93
91
64
CI
0.0
0.0
0.393E-01
0.709E-02
0.411E-02
0.411E-02
0.168E-01
0.167E-01
0.167E-01
0.0
0.562E-02
0.0
C.O
C.337E-02
C.O
0.0
0.0
0.0
0.0
0.0
0.411E-03
0.411E-03
0.0
0.0
0.0
RANK
61
62
48
89
92
93
49
44
46
102
11
56
55
17
99
103
53
104
63
65
91
94
107
105
58
CI
0.0
0.0
0.0
0.0
0.0
0.0
G.O
C.O
0.0
0.0
0.281E-03
0.0
€.0
0.168E-03
0.0
9.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
RANK
46
47
31
1
2
3
32
27
29
71
19
39
38
18
69
72
36
73
48
50
6
7
76
74
42
CI
0.0
0.0
0.0
0.709E-02
0.411E-02
0.411E-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
0.411E-03
0.411E-03
0.0
0.0
0.0
-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
CRITICALITV INDEX RANKING - OEM SALES VOLUME
PRINCIPAL RANKING - CO
EARLY MODEL
PART PART
CODE NAME
1. 3. 8 REBUILDING KITS
1. 3. 9 FLOAT AND VALVE
1. 3. 4 CHCKE MECHANISM
1. 3. 6 POWER VALVES
5. 1. 1 VALVE LIFTER/SPR
1. 1. 2 REBUILT CARB
5. 1. 4 VALVE SEALS
5. I. 5 EXHAUST VALVES
1. 1. 1 NEW CARB
I. 3. 5 ACCELERATOR PUMP
1. 3. 2 METERING RODS
3. 2. 0 AIR CLEANER ELEM
1. 3. 1 METERING JETS
6. 1. 1 PCV VALVE
1. 3. 3 VAC BRK VALVE
6. 1. 3 PCV FRSHAIR FLTR
1. 2. 1 IDLE STPSCLENOID
5. 1. 3 VALVE GUIDES
5. 2. 0 PISTON RINGS
1. 1. 3 SPECIALTY CARB
6. 3. 2 AI HOSES
6. 3. 7 AI PUMP/BELTS
4.12. 0 FI STARTING VALV
1. 2. 2 THROTTLE DASHPOT
5. 4. 1 HEAD GASKETS
RANK
3
7
8
9
4
11
5
6
14
35
40
42
43
32
34
41
45
21
22
29
27
28
55
68
44
• ML ~
CI
0.786E-02
0.337E-02
0.334E-02
0.334E-02
0.709E-02
0.290E-02
0. 4116-02
0.411E-02
0.174E-02
0.168E-03
0.117E-03
0.106E-03
0.103E-03
0.195E-03
0.170E-03
0.108E-03
0.709E-04
0.411E-03
0.411E-03
0.205E-03
0.221E-03
0.221E-03
0.284E-04
0.132E-04
0.981E-04
w^* »^
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
LU
CI
0.393E-01
0.168E-01
0.167E-01
0.167E-01
0.709E-02
0.562E-02
0.411E-02
0.411E-02
0.337E-02
0.337E-02
0.235E-02
0.211E-02
0.205E-02
0.195E-02
0.170E-02
0.108E-02
0.709E-03
Q.411E-03
0.411E-03
0.397E-03
0.221E-03
0.221E-03
0.142E-03
0.132E-03
0.981E-04
RANK
48
49
44
46
89
11
92
93
17
45
42
73
41
98
43
100
38
91
94
14
109
114
87
39
96
NUA —
CI
0.0
0.0
0.0
0.0
0.0
0.281E-03
0.0
0.0
0.168E-03
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
c.o
0.0
0.199E-03
0.0
0.0
0.0
0.0
0.0
RANK
31
32
27
29
1
19
2
3
18
28
25
4
24
68
26
70
21
6
7
20
78
83
65
22
8
:>nu*e — —
CI
0.0
0.0
0.0
0.0
0.709E-02
0.0
0.411E-02
0.411E-02
0.0
6.0
0.0
0.528E-03
0.0
0.0
0.0
0.0
0.0
0.411E-03
0.411E-03
0.0
0.0
0.0
0.0
0.0
0.981E-04
-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
i
01
PART
CODE
6.
6.
2.
6.
6.
6.
6.
6.
6.
6.
1.
6.
6.
1.
6.
6.
1.
6.
6.
6.
6.
6.
6.
6.
7.
4.
4.
3.
4.
10.
4.
5.
5.
5.
4.
1.
5.
7.
1.
4.
5.
1.
4.
4.
4'.
4.
7.
8.
8.
3.
1
3
7
8
7
2
8
6
1
4
2
3
1
3
10
5
1
11
5
7
6
4
5
1
2
CRITICALITY INDEX RANKING - OEM SALES VOLUME
PRINCIPAL RANKING - NOX
EARLY MODEL
PART
NAME
EGR VALVES
EGR THERMO VALVE
SPARK DELAY VLV
EGR VAC AMP
THERMO VAC VALV
EGR HOSES/SEALS
TCS TEMP SWITCH
TCS TRANS SWITCH
TCS VAC SOLENOID
EGR SOLENOID VLV
REBUILT CARB
TCS TIME DELAY
OSAC VAC ORIFICE
SPECIALTY CARB
EGR CARB SPACER
TCS THERMO VALVE
NEW CARB
EGR BACKPRES SEN
EGR TEMP SWITCH
EGR TIME DELAY
EGR SPEED/TRANS
OSAC VAC BYPASS
ESC SPEED SWITCH
ESC ELEC MODULE
EXHAUST MANIFOLD
RANK
115
116
38
52
54
57
60
63
64
U7
11
69
62
29
122
72
14
123
118
120
119
73
79
85
49
ni. — —
CI
0.0
0.0
0.122E-03
0.357E-04
0.340E-04
0.227E-04
0.216E-04
0.187E-04
0.176E-04
0.0
0.290E-02
0.119E-04
0.204E-04
0.205E-03
0.0
0.851E-05
0.174E-02
0.0
0.0
0.0
0.0
0.851E-05
0.397E-05
0.284E-05
0.545E-04
•"^ ^^
RANK
95
97
65
102
131
96
112
110
107
98
6
108
117
20
104
109
9
105
99
101
100
119
124
121
30
cu
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.562E-02
0.0
0.0
Q.397E-03
0.0
0.0
0.337E-02
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.545E-04
RANK
1
2
3
4
5
6
7
a
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
CI
0.463E-02
0.211E-02
0.122E-02
0.715E-03
0.681E-03
0.454E-03
0.431E-03
0.374E-03
Q.352E-03
0.306E-03
0.281E-03
0.238E-03
0.204E-03
0.199E-03
0.187E-03
0.170E-03
0.168E-03
0.159E-03
0.148E-03
0.148E-03
0.125E-03
0.851E-04
0.794E-04
0.567E-04
0.545E-04
RANK
84
86
44
91
129
85
103
101
96
87
19
98
109
20
93
100
18
94
88
90
89
112
118
114
133
anuK
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
CI
-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
CRITICALITY INDEX RANKING - OEM SALES VOLUME
PRINCIPAL RANKING - SMOKE
EARLY MODEL
PART
CODE
5.
5.
5.
3.
4.
5.
5.
5.
5.
4.
4«
6.
3.
5.
3.
4.
4.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
2.
5.
1.
2.
4.
1.
4.
3.
1.
5.
5.
4.
8.
2.
1.
1.
1.
2.
2.
2.
3.
3.
1
4
5
0
0
3
0
1
2
6
0
4
0
0
0
0
0
1
2
3
1
2
3
1
2
PART
NAME
VALVE LIFTER/SPR
VALVE SEALS
EXHAUST VALVES
AIR CLEANER ELEM
MFI VALVES
VALVE GUIDES
PISTON RINGS
HEAD GASKETS
VALVE CAM LOBES
FI THROTTLE VALV
FI PRES SENS/REG
PCV OIL SEPARATR
SUPERCHARGER
CAMSHAFTS
TURBQCHARGER
FI DIST MANIFOLD
FI HI PRES PUMP
NEW CARB
REBUILT CARB
SPECIALTY CARB
IDLE STPSCLENOID
THROTTLE DASHPCT
THRTTL PGSITIONR
METERING JETS
METERING RODS
RANK
4
5
6
42
107
21
22
44
61
106
91
53
77
83
88
99
100
14
11
29
45
68
75
43
40
HI, —
CI
0.709E-02
0.411E-02
0.411E-02
0.106E-03
0.0
0.411E-03
0.411E-03
0.981E-04
0.210E-04
0.0
0.170E-05
0.352E-04
0.567E-05
0.284E-05
0.189E-05
0.420E-06
0.630E-07
0.174E-02
0.290E-02
0.205E-03
0.709E-04
0.132E-04
0.662E-05
0.103E-03
0.117E-03
_«**
RANK
5
7
8
12
80
18
19
25
36
79
38
32
42
50
48
55
56
9
6
20
17
24
28
13
11
uu
CI
0.709E-02
0.411E-02
C.411E-02
0.211E-02
0.0
C.411E-03
0.411E-03
C.981E-04
C.210E-04
C.O
0.170E-04
0.340E-04
0.113E-C4
0.284E-05
0.378E-05
0.315E-06
0.630E-07
0.337E-02
0.562E-02
0.397E-03
C.709E-03
0.132E-03
G.662E-G4
C.205E-02
0.235E-02
RANK
89
92
93
73
81
91
94
96
90
80
79
101
76
97
75
37
78
17
11
14
38
39
40
41
42
CI
0.0
0.0
G.O
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
o.o
0.0
0.0
C.O
0.315E-06
0.0
0.168E-03
0.281E-03
0.199E-03
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
anuisc — —
CI
0.709E-02
0.411E-02
0.411E-02
0.528E-03
0.454E-03
0.411E-03
0. 4116-03
0.981E-04
0.210E-04
0.156E-04
0.936E-05
0.340E-05
0.312E-05
0.284E-05
0.104E-05
0.315E-06
0.630E-07
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 - GARAGE SALES
PRINCIPAL RANKING - HC
EARLY MODEL
PART
CODE
2. 5. 0
2. 6. 0
2. 3. 1
2. 3. 2
1. 3. 8
1- 3. 9
2. 1. 0
5. 1. 1
5. 1. 5
1. 1. 2
5. 1. 4
2. 2. 0
2. 4. 0
2.10. 0
1. 1. 1
6. 1. 1
5. 2. 0
3. 2. 0
7. 3.
1. 4.
5. 1.
1. 1. 3
5. 4. 1
5. 1. 2
5. 5. 0
2
0
3
PART
NAME
SPARK PLUGS
IGMTICM HIRES
CAP
ROTOR
REBUILDING KITS
FLOAT AND VALVE
POINTS
VALVE LIFTER/SPR
EXHAUST VALVES
REBUILT CAHB
VALVE SEALS
CONDENSER
MAG/OPT TRIGGERS
El CONTROL CIRCT
NEW CAR8
PCV VALVE
PISTON RINGS
AIR CLEANER ELEM
EXHAUST MANIFOLD
FUEL FILTER
VALVE GUIDES
SPECIALTY CARS
HEAD GASKETS
VALVE CAM LOBES
CAMSHAFTS
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
rn,
CI
0.266E+00
0.127E+00
0.168E-01
0.168E-01
0.950E-02
0.410E-02
0.281E-02
0.240E-02
0.159E-02
0.109E-02
0.109E-02
0.561E-03
0.447fc-03
0.447E-03
0.388E-03
0.295E-03
0.278E-03
0.244E-03
0.215E-03
0.167E-03
0.109E-03
Q.448E-04
0.224E-04
0.721E-05
0.721E-05
RANK
42
43
34
35
1
2
32
5
7
6
8
33
41
47
9
4
10
3
11
31
12
13
14
15
16
uu
CI
0.0
0.0
0.0
c.o
0.475E-01
0.205E-01
0.0
C.240E-02
0.159t-02
C.212h-02
C.109E-02
0.0
C.O
0.0
C.750E-03
C.295E-02
0.278E-03
0.487E-02
C.215E-03
C.O
0.109E-03
0.867t-04
0.224E-04
C.72lt-C5
C.721E-05
RANK
31
32
23
24
16
17
21
60
64
2
63
22
30
36
4
69
65
43
1
2C
62
3
67
61
68
CI
:.o
C.O
0.0
0.0
0.0
0.0
0.0
3.0
0.0
D.106E-C3
C.O
0.0
0.0
C.O
3.375E-J4
0.0
C.O
0.0
0.215E-03
0.0
0.0
0.433E-04
0.0
0.0
0.0
RANK
39
40
31
32
24
25
29
1
2
12
4
30
38
44
11
67
5
3
133
28
6
13
7
8
9
inuNt ----
CI
O.G
0.0
O.C
0.0
0.0
0.0
0.0
0.240E-02
0.159E-02
0.0
0.109E-02
0.0
0.0
0.0
0.0
0.0
0.278E-03
0.122E-02
0.0
0.0
0.109E-03
0.0
0.224E-04
0.721E-05
0.721E-05
-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
PART
CODE
1. 3. 8
1. 3. 9
3. 2. 0
6. 1. 1
5. 1. 1
1. 1. 2
f 5. 1. 5
oo 5. 1. 4
1. 1. 1
5. 2. 0
7. 3. 2
5. 1. 3
1. 1. 3
5. 4. 1
5. 1. 2
5. 5. 0
7. 3. 1
4. 2. 0
1. 2. 1
1. 2. 2
1. 2. 3
1. 3. 1
1. 3. 2
1. 3. 3
1. 3. 4
PART
NAPE
REBUILDING KITS
FLOAT AND VALVE
AIR CLEANER ELEM
PCV VALVE
VALVE LIFTER/SPR
REBUILT CARS
EXHAUST VALVES
VALVE SEALS
NEW CARB
PISTON RINGS
EXHAUST MANIFOLD
VALVE GUIDES
SPECIALTY CARB
HEAD GASKETS
VALVE CAM LOBES
CAMSHAFTS
HIGH PERF EXHAST
FI HI PRES PUMP
IDLE STPSCLENOID
THROTTLE OASHPCT
THRTTL POSITIONR
METERING JETS
METERING RODS
VAC BRK VALVE
CHOKE MECHANISM
NDEX
IPAL
EARLY
RANK
5
6
18
16
8
10
9
11
15
17
19
21
22
23
24
25
26
27
28
29
30
31
32
33
34
RANKING - G
RANKING - C
MODEL
HC
CI
0.950E-02
0.410E-02
0.244E-03
0.295E-03
0.240E-02
0.109E-02
0.159E-02
0.109E-02
0.388E-03
0.278E-03
0.215E-03
0.109E-03
0.448E-04
0.224E-04
0.721E-05
0.721E-05
0.917E-06
0.101E-07
0.0
0.0
0.0
0.0
0.0
0.0
0.0
ARAGE
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
SALES
f rfc
CI
0.475E-01
0.205E-01
0.487E-02
0.295E-02
0.240E-02
0.212E-02
0.159E-02
0.109E-02
0.750E-03
0.278E-03
0.215E-03
0.109E-03
0.867E-04
0.224E-04
0.721E-05
0.721E-05
0.917E-C6
0.101E-07
0.0
0.0
0.0
0.0
0.0
0.0
0.0
RANK
16
17
43
69
60
2
64
63
4
65
1
62
3
67
61
68
5
48
6
7
8
9
i-e
11
12
CI
0.0
0.0
0.0
0.0
0.0
0.106E-03
0.0
0.0
0.375E-04
0.0
0.215E-03
0.0
0.433E-04
0.0
0.0
0.0
0.917E-06
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
RANK
24
25
3
67
1
12
2
4
11
5
133
6
13
7
8
9
132
10
14
15
16
17
18
19
20
SMOKE
CI
0.0
0.0
0.122E-02
0.9
0.240E-02
0.0
0.159E-02
0.109E-02
0.0
0.278E-03
0.0
0.109E-03
0.0
0.224E-04
0.721E-05
0.721E-05
0.0
0.101E-07
0.0
0.0
0.0
0.0
0.0
0.0
0.0
-------
PART
CODE
7. 3, 2
1. 1. 2
1. 1. 3
1. 1. 1
7. 3. 1
1. 2. 1
1. 2. 2
1. 2. 3
1. 3. 1
1. 3.
1. 3.
1. 3. 4
1. 3. 5
1. 3. 6
1. 3. 7
1. 3. 8
1. 3. 9
1. 3.10
1. 3.11
1. 4. 0
2. 1. 0
2. 2. 0
2. 3. 1
2. 3. 2
2. 3. 3
2
3
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
CRITICALITY INDEX RANKING - GARAGE SALES
PRINCIPAL RANKING - NOX
EARLY MODEL
PART
NAPE
EXHAUST MANIFOLD
REBUILT CARB
SPECIALTY CARS
NEW CARB
HIGH PERF EXHAST
IDLE STPSGLENOID
THROTTLE OASHPOT
THRTTL PCSITIONR
METERING JETS
METERING RODS
VAC BRK VALVE
CHGKE MECHANISM
ACCELERATOR PUMP
POWER VALVES
GASKETS
REBUILDING KITS
FLOAT AND VALVE
IDLE ADJUSTMENT
IDLE ENRICHMENT
FUEL FILTER
POINTS
CONDENSER
CAP
ROTOR
MECH ADVANCE
RANK
19
10
22
15
26
28
29
30
31
32
33
34
35
36
37
5
6
38
39
20
7
12
3
4
40
nu -— —
CI
0.2156-03
0.109E-02
0.448E-04
0.388E-03
0.917E-06
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.950E-02
0.410E-02
0.0
0.0
0.167E-03
0.281E-02
0.561E-03
0.168E-01
0.168E-01
0.0
RANK
11
6
13
9
17
19
20
21
22
23
24
25
26
27
28
1
2
29
30
31
32
33
34
35
36
CI
0.215E-03
0.212E-02
0.867E-04
C.750E-03
G.917E-06
C.O
0.0
0.0
0.0
0.0
0.0
C.O
C.O
0.0
0.0
0.475E-01
0.205E-01
C.O
0.0
0.0
0.0
C.O
0.0
0.0
0.0
RANK
1
2
3
4
5
6
7
8
9
1C
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
CI
D.215E-03
0.106E-03
0.433E-04
0.375E-G4
0.917E-06
r.o
0.0
0.0
0.0
0.0
0.0
3.0
0.0
1.0
0.0
0.0
0.0
C.O
0.0
0.0
0.0
0.0
0.0
0.0
0.0
RANK
133
12
13
11
132
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
iPIUIV
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
0.3
CI
-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
CRITICALITY INDEX RANKING - GARAGE SALES
PRINCIPAL RANKING - SMOKE
EARLY MODEL
PART
CODE
5.
5.
3.
5.
3> 5.
^ 5.
0 5.
5.
5.
4.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
2.
1.
2.
1.
4.
1.
5.
2.
1.
1.
1.
2.
2.
2.
3.
3.
3.
3.
3.
3.
3.
3.
3.
1
5
0
4
0
3
1
2
0
0
1
2
3
1
2
3
1
2
3
4
5
6
7
8
9
PART
NAPE
VALVE LIFTER/SPR
EXHAUST VALVES
AIR CLEANER ELEM
VALVE SEALS
PISTON RINGS
VALVE GUIDES
HEAD GASKETS
VALVE CAM LOBES
CAMSHAFTS
FI HI PRES PUMP
NEW CARB
REBUILT CARB
SPECIALTY CARB
IDLE STPSOLENOID
THROTTLE DASHPCT
THRTTL POSITIONR
METERING JETS
METERING RODS
VAC BRK VALVE
CHOKE MECHANISM
ACCELERATOR PUMP
POWER VALVES
GASKETS
REBUILDING KITS
FLOAT AND VALVE
RANK
8
9
18
11
17
21
23
24
25
27
15
10
22
28
29
30
31
32
33
34
35
36
37
5
6
ML
CI
0.240E-02
0.159E-02
0.244E-03
0.109E-02
0.278E-03
0.109E-03
0.224E-04
0.721E-05
0.721E-05
0.101E-07
0.388E-03
0.109E-02
0.448E-04
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.950E-02
0.410E-02
RANK
5
7
3
8
10
12
14
15
16
18
9
6
13
19
20
21
22
23
24
25
26
27
28
1
2
LU
CI
G.240E-02
0.159E-02
0.487E-02
C.109E-02
0.278E-03
0.109E-03
C.224E-04
0.721E-05
C.721E-05
0.101E-07
Q.750E-03
0.212E-02
0.867E-04
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.475E-01
0.205E-01
RANK
60
64
43
63
65
62
67
61
68
48
4
2
3
6
7
8
9
10
11
12
13
14
15
16
17
I^UA
CI
0.0
0.0
0.0
c.o
0.0
0.0
0.0
G.O
0.0
0.0
0.375E-04
0.106E-03
0.433E-04
0.0
0.0
0.0
0.0
J.O
0.0
0.0
0.0
0.0
0.0
c.o
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
inuivc — —
CI
0.240E-02
0.159E-02
0.122E-02
0.109E-02
0.278E-03
0.109E-03
0.224E-04
0.721E-05
0.721E-05
0.101E-07
0.0
0.0
0.0
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. 68-01-1*57
CRITICALITY INDEX RANKING
PRINCIPAL RANKING
EARLY MODEL
WAREHOUSE SALES
HC
PART PART
CODE NAME
2. 5. 0 SPARK PLUGS
2. 6. 0 IGNITICN WIRES
1. 3. 8 REBUILDING KITS
1. 1. 2 REBUILT CARB
2. 3. 2 ROTOR
2. 3. 1 CAP
1. 3. 4 CHOKE MECHANISM
1. 1. 1 NEW CARB
5. 1. 1 VALVE LIFTER/SPR
2. 1. 0 POINTS
5. 1. 4 VALVE SEALS
5. 1. 5 EXHAUST VALVES
1. 1. 3 SPECIALTY CARB
2. 7. 0 COIL
2. 2. 0 CONDENSER
6. 1. 1 PCV VALVE
3. 2. 0 AIR CLEANER ELEM
2. 3. 7 SPARK DELAY VLV
1. 4. 0 FUEL FILTER
2. 3. 5 DISTRIBUTCR DRIV
6. 2. 3 EVAP FRSH AIR
6. 3. 2 AI HOSES
5. 1. 3 VALVE GUIDES
5. 4. 1 HEAD GASKETS
5. 2. 0 PISTON RINGS
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
CI
0.446E+00
0.340E-01
0.169E-01
0.608E-02
0.539E-02
0.459E-02
0.384E-02
0.379E-02
0.272E-02
0.146E-02
0.919E-03
0.919E-03
0.442E-03
0.426E-03
0.293E-03
0.161E-03
0.155E-03
0.148E-03
0.105E-03
0.105E-03
0.100E-03
0.100E-03
0.919E-04
0.910E-04
0.901E-04
RANK
49
50
1
3
44
43
2
4
6
41
8
9
10
51
42
7
5
47
40
45
79
16
17
18
19
uu — — —
CI
0.0
0.0
0.846E-01
G.118E-C1
C.O
0.0
C.192E-01
C.733E-02
0.272E-02
C.O
C.919E-03
C.919E-03
0.856E-03
C.O
0.0
C.161E-02
C.310E-02
0.0
C.O
0.0
0.0
C.100E-03
0.919E-C4
0.910E-04
0.901E-04
RANK
36
37
23
4
31
30
19
6
65
28
68
69
5
38
29
74
48
2
27
33
80
85
67
72
70
CI
0.0
0.0
0.0
0.589E-03
0.0
0.0
C.O
0.367E-Q3
0.0
0.0
0.0
0.0
0.428E-03
0.0
0.0
0.0
0.0
3.148E-02
0.0
0.0
0.0
0.0
0.0
C.O
0.0
RANK
40
41
25
13
33
32
21
12
1
30
2
3
14
42
31
67
4
38
29
36
73
78
6
7
8
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.272E-02
0.0
0.919E-03
0.919E-03
0.0
0.0
0.0
0.0
0.776E-03
0.0
0.0
0.0
0.0
0.0
0.919E-04
0.910E-04
0.901E-04
-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
PART
CODE
1.
1.
1.
1.
3.
5.
6.
5.
5.
1.
1.
6.
1.
1.
6.
6.
5.
5.
5.
5.
2.
6.
3.
2.
5.
3.
3.
1.
1.
2.
1.
1.
1.
1.
1.
3.
1.
2.
2.
10.
3.
1.
4.
2.
5,
3.
3.
3.
3.
1.
8
4
2
1
0
1
1
4
5
3
3
3
1
2
4
2
3
1
0
0
4
7
0
3
2
PART
NAME
REBUILDING KITS
CHCKE MECHANISM
REBUILT CARB
NEW CARB
AIR CLEANER ELEM
VALVE LIFTER/SPR
PCV VALVE
VALVE SEALS
EXHAUST VALVES
SPECIALTY CARB
VAC BRK VALVE
PCV FRSHAIR FLTR
IDLE STPSCLENOID
THROTTLE DASHPOT
DECEL VALVE
AI HOSES
VALVE GUIDES
HEAD GASKETS
PISTON RINGS
CAMSHAFTS
VACUUM ADVANCE
AI PUMP/BELTS
INTAKE MANIFOLD
MECH ADVANCE
VALVE CAM LOBES
NDEX
IPAL
EARLY
RANK
3
7
4
8
17
9
16
11
12
13
28
31
33
36
37
22
23
24
25
26
62
41
44
45
46
RANKING - WAREHOU
RANK ING - CO
MODEL
HC
CI
0.169E-01
0.384E-02
0.608E-02
0.379E-02
0.155E-03
0.272E-02
0.161E-03
0.919E-03
0.919E-03
0.442E-03
0.787E-04
0.495E-04
0.407E-04
0.210E-04
0.133E-04
0.100E-03
0.919E-04
0.910E-04
0.901E-04
0.901E-04
0.0
0.819E-05
0.653E-05
0.588E-05
0.500E-05
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
SE SALES
CI
C.846E-01
0.192E-01
0.118E-01
C.733E-02
0.310E-02
0.272E-02
C.161E-02
0.919E-03
C.919E-03
0.856E-03
C.787E-03
C.495E-03
C.407E-03
C.210E-03
0.133E-03
C.100E-03
C.919E-C4
C.910E-04
0.901E-04
C.901E-C4
0.251E-04
0.819E-C5
C.653E-05
C.588E-05
C.5CGE-C5
RANK
23
19
4
6
48
65
74
68
69
5
18
76
13
14
129
85
67
72
70
73
32
90
49
1C
66
Mnv _____
CI
0.0
0.0
0.589E-03
0.367E-03
0,0
0.0
3.0
0.0
0.0
0.428E-03
0.0
0.0
G.O
0.0
0.0
0.0
G.O
0.0
0.0
0.0
%0
0.0
c.o
3.588E-04
C.O
RANK
25
21
13
12
4
1
67
2
3
14
20
69
15
16
126
78
6
7
8
9
35
83
52
34
10
SMOKE
CI
0.0
0.0
0.0
0.0
0.776E-03
0.272E-02
0.0
0.919E-03
0.919E-03
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.919E-04
0.910E-04
0.901E-04
0.901E-04
0.0
0.0
0.0
0.0
0.500E-05
-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
CRITICALITY INDEX RANKING - WAREHOUSE SALES
PRINCIPAL RANKING - NOX
EARLY MODEL
PART PART
CODE NAKE
6.10. 7 THERMO VAC VALV
2. 3. 7 SPARK DELAY VLV
6. 4. 1 EGR VALVES
1. 1. 2 REBUILT CARB
1. 1. 3 SPECIALTY CARB
1. 1. 1 NEW CARB
6. 4. 8 EGR VAC AMP
6. 5. 1 TCS VAC SOLENOID
6. 5. 8 TCS TEMP SWITCH
2. 3. 3 MECH ADVANCE
7. 3. 2 EXHAUST MANIFOLD
7. 3. 1 HIGH PERF EXHAST
1. 2. 1 IDLE STPSCLENOID
1. 2. 2 THROTTLE DASHPOT
1. 2. 3 THRTTL PCSITIONR
1. 3. 1 METERING JETS
1. 3. 2 METERING RODS
1. 3. 3 VAC BRK VALVE
1. 3. 4 CHOKE MECHANISM
1. 3. 5 ACCELERATOR PUMP
1. 3. 6 POWER VALVES
1. 3. 7 GASKETS
1. 3. 8 REBUILDING KITS
1. 3. 9 FLOAT AND VALVE
1. 3.10 IDLE ADJUSTMENT
RANK
27
18
92
A
13
8
38
40
42
45
50
52
33
36
53
54
55
28
7
56
57
58
3
59
60
CI
0.882E-04
0.148E-03
0.0
0.608E-02
0.442E-03
0.379E-02
0.132E-04
0.826E-05
0.779E-05
0.588E-05
0.490E-06
0.647E-07
0.407E-04
0.210E-04
0.0
0.0
0.0
0.787E-04
0.384E-02
0.0
0.0
0.0
0.169E-01
0.0
0.0
RANK
131
47
87
3
10
4
94
99
106
24
28
30
13
14
31
32
33
11
2
34
35
36
1
37
38
uu
CI
0.0
0.0
0.0
0.118E-C1
0.856E-03
0.733E-02
C.O
C.O
0.0
0.588E-05
0.490E-06
0.647E-07
C.407E-C3
C.21CE-C3
C.O
C.O
0.0
0.787E-03
0.192E-01
C.O
0.0
0.0
0.846E-01
0.0
C.O
* — ""~ "•"*•
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
CI
D.176E-02
0.148E-02
0.928E-03
0.589E-03
0.428E-03
0.367E-03
0.265E-03
0.165E-03
0.156E-03
0.588E-04
Q.490E-06
0.647E-07
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
o.o
C.O
0.0
o.o
0.0
RANK
129
38
84
13
14
12
91
96
103
34
133
132
15
16
17
18
19
20
21
22
23
24
25
26
27
snu*
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
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
CI
-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
CRITICALITY INDEX RANKING - WAREHOUSE SALES
PRINCIPAL RANKING - SMOKE
EARLY MODEL
PART
CODE
5. 1.
5. 1.
5. 1.
3>
I
i—"
^
3.
4.
5.
5.
5.
5.
5.
4.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
2.
4.
1.
4.
2.
5.
1.
2.
1.
1.
1.
2.
2.
2.
3.
3.
3.
3.
3.
3.
3.
3.
1
4
5
0
0
3
1
0
0
2
0
1
2
3
1
2
3
1
2
3
4
5
6
7
8
PART
NAME
VALVE LIFTER/SPR
VALVE SEALS
EXHAUST VALVES
AIR CLEANER ELEM
FI THROTTLE VALV
VALVE GUIDES
HEAD GASKETS
PISTON RINGS
CAMSHAFTS
VALVE CAM LOBES
FI HI PRES PUMP
NEW CAK8
REBUILT CARB
SPECIALTY CARB
IDLE STPSCLENOID
THROTTLE DASHPCT
THRTTL PCSITIONR
METERING JETS
METERING RODS
VAC BRK VALVE
CHCKE MECHANISM
ACCELERATOR PUMP
POWER VALVES
GASKETS
REBUILDING KITS
RANK
9
11
12
17
70
23
24
25
26
46
51
8
4
13
33
36
53
54
55
28
7
56
57
58
3
ML
CI
0.272E-02
0.919E-03
0.919E-03
0.155E-03
0.0
0.919E-04
0.910E-04
0.901E-04
0.901E-04
0.500E-05
0.183E-06
0.379E-02
0.608E-02
0.442E-03
0.407E-04
0.210E-04
0.0
0.0
0.0
0.787E-04
0.384E-02
0.0
0.0
0.0
0.169E-01
RANK
6
8
9
5
64
17
18
19
20
25
29
4
3
10
13
14
31
32
33
11
2
34
35
36
1
cu
CI
C.272E-02
C.919E-03
0.919E-03
C.310E-02
0.0
C.919E-04
0.910E-04
C.901E-04
0.901E-04
0.500E-05
C.183E-06
C.733E-02
0.118E-01
C.856E-03
C.407E-03
0.210E-03
0.0
C.O
0.0
C.787E-03
C.192E-01
C.O
0.0
0.0
0.846E-01
RANK
65
68
69
48
55
67
72
70
73
66
53
6
4
5
13
14
15
16
17
18
19
20
21
22
23
CI
0.0
G.O
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.367E-03
0.589E-03
0.428E-03
G.O
0.0
Q.O
0.0
0.0
0.0
o.o
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
anuisc — — — -
CI
0.272E-02
0.919E-03
0.919E-03
0.776E-03
0.970E-04
0.919E-04
0.910E-04
0.901E-04
0.901E-04
0.500E-05
0.183E-06
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
-------
AUTCMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
CRITICALITY INDEX RANKING - OEM SALES VOLUME
PRINCIPAL RANKING - HC
LATE MODELS
PART
CODE
2.
2.
1.
1.
1.
3> 1.
1 6.
en 1.
6.
6.
2.
2.
1.
1.
3.
3.
6.
6.
6.
5.
1.
6.
3.
3.
6.
5.
6.
3.
3.
3.
3.
2.
1.
10.
1.
3.
3.
1.
3.
1.
1.
1.
1.
2.
1.
2.
2.
1.
1.
3.
0
0
8
9
4
6
1
2
1
1
2
1
1
3
3
4
3
2
2
1
1
3
1
2
2
PART
NAME
SPARK PLUGS
IGNITION MIRES
REBUILDING KITS
FLOAT AND VALVE
CHCKE MECHANISM
POWER VALVES
EVAP CANISTER
REBUILT CARB
HEAT RISER
PCV VALVE
ROTOR
CAP
NEW CARB
VAC BRK VALVE
TAC VAC MCTOR
TAC VAC HCSES
PCV FRSHAIR FLTR
PCV HCSES
EVAP HCSES
VALVE LIFTER/SPR
IDLE STPSCLENCID
EVAP FRSH AIR
TAC SHROUC
TAC THERMOSTAT
AI HOSES
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
CI
0.189E+00
0.677E-01
0.786E-02
0.337E-02
0.334E-02
0.334E-02
0.318E-02
0.290E-02
0.238E-02
0.195E-02
0.187E-02
0.185E-02
0.174E-02
0.170E-02
0.141E-02
0.141E-02
0.108E-02
0.107E-02
0.107E-02
0.709E-03
0.709E-03
0.569E-03
0.550E-03
0.550E-03
0.441E-03
RANK
12
22
1
2
3
4
90
5
27
11
37
38
6
13
31
32
16
52
53
20
21
91
79
80
14
CI
0.189E-02
C.677E-03
C.393E-01
0.168E-01
0.167E-01
0.167E-01
0.0
0.562E-02
0.238E-03
0.195E-02
0.936E-04
C.927E-04
C.337E-02
0.170E-02
0.141E-G3
0.141E-03
0.108E-02
0.312E-C4
0.312E-04
0.709E-C3
0.709E-03
0.0
0.0
C.O
C.110E-02
RANK
61
62
48
49
44
46
102
11
127
98
56
55
17
43
70
71
100
99
1C3
89
38
104
68
69
109
INUA —
CI
0.0
0.0
0.0
0.0
0.0
0.0
3.0
0.281E-03
0.0
0.0
0.0
0.0
0.168E-03
0.0
0.0
0.0
0.0
0.0
0.0
C.O
C.O
0.0
0.0
0.0
C.O
RANK
46
47
31
32
27
29
71
19
123
68
39
38
18
26
55
56
70
69
72
1
21
73
53
54
78
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
0.709E-02
0.0
0.0
0.0
0.0
0.0
-------
cr>
0
1
PART
CODE
1. 3. 8
1. 3. 9
1. 3. 4
1. 3. 6
1. 1. 2
1. 1. 1
1. 3. 5
1. 3. 2
3. 2.
1. 3.
6. 1. 1
2. 5. 0
1. 3. 3
6. 3. 2
6. 3. 7
6. 1. 3
1. 1. 3
2. 3. 4
6. 3. 5
5. 1. 1
1. 2. 1
2. 6. 0
5. 1. 4
5. 1. 5
6. 3. 1
AUTOCTIVE PARTS STUDY - EPA CONTRACT NO. 68-C1-1957
CRITICALITY INDEX RANKING - OEM SALES VOLUME
PRINCIPAL RANKING - CO
LATE MODELS
PART
NAPE
REBUILDING KITS
FLCAT AND VALVE
CHCKE KECH4AIISK
POWER VALVES
REBUILT CARS
NEW CARB
ACCELERATOR PUMP
METERING RODS
AIR CLEANER ELEM
METERING JETS
PCV VALVE
SPARK PLUGS
VAC BRK VA1VE
AI HOSES
AI PUMP/BELTS
PCV FRSHAIR FLTR
SPECIALTY CARB
VACUUM ADVANCE
AI BYPASS/DVRTR
VALVE LIFTER/SPR
IDLE STPSCLENOID
IGNITICN WI«ES
VALVE SEALS
EXHAUST VALVES
AI MANIFOLD
RANK
3
4
5
6
8
13
38
42
44
45
10
1
14
25
26
17
29
102
32
20
21
2
27
28
43
HL
CI
0.786E-02
0.337E-02
0.334E-02
0.334E-02
0.290E-02
0.174E-02
0.168E-03
0.117E-03
0.1Q6E-03
0.103E-03
0.195E-02
0.189E+00
0.170E-02
0.441E-03
0.441E-03
0.108E-02
0.404E-03
0.0
0.315E-03
0.709E-03
0.709E-03
0.677E-01
0.411E-03
0.411E-03
0.109E-03
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
uu
CI
0.393E-01
G.168E-01
C.167E-01
C.167E-01
C.562E-02
C.337E-02
C.337E-C2
C.235E-02
0.211E-02
0.205E-02
G.195E-Q2
0.189E-C2
0.170E-02
0.110E-02
C.110E-02
0.108E-C2
C.993E-03
C.936E-03
C.788E-03
C.709E-03
0.709E-03
0.677E-03
0.411E-03
0.411E-03
0.272E-03
RANK
48
49
44
46
11
17
45
42
73
41
98
61
43
109
114
100
14
57
112
89
38
62
92
93
108
CI
0.0
0.0
0.0
0.0
0.281E-03
0.168E-03
C.O
0.0
0.0
0.0
0.0
0.0
C.O
C.O
0.0
0.0
0.199E-03
0.0
0.0
C.O
0.0
0.0
0.0
0.0
0.0
RANK
31
32
27
29
19
18
26
25
4
24
68
46
26
78
83
70
20
41
81
1
21
47
2
3
77
^nuist — —
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.704E-03
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.709E-02
0.0
0.0
0.411E-02
0.411E-02
0.0
-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
I
I—•
~«l
PART
CODE
6. 4. 1
6. 4. 3
2. 3. 7
6. 4. 8
6.10. 7
6. 4. 2
6. 5. 8
6. 5. 6
6. 5. 1
6. 4. 4
1. 1. 2
6. 5. 3
6. 7. 1
1. 1. 3
6. 4.10
6. 5. 5
1. 1. 1
6. 4.11
6. 4. 5
6. 4. 7
6. 4.
6. 7.
6. 8. 5
6. 8. 1
7. 3. 2
6
4
CRITICALITY INDEX RANKING - OEM SALES VOLUME
PRINCIPAL RANKING - NOX
LATE MODELS
PART
NAME
EGR VALVES
EGR THERMO VALVE
SPARK DELAY VLV
EGR VAC AMP
THERMO VAC VALV
EGR HOSES/SEALS
TCS TEMP SWITCH
TCS TRANS SWITCH
TCS VAC SCLENOID
EGR SOLENOID VLV
REBUILT CARB
TCS TIME DELAY
OSAC VAC ORIFICE
SPECIALTY CARS
EGR CAKB SPACER
TCS THERMC VALVE
NEW CARB
EGK BACKPRtS SEN
EGR TEMP SWITCH
EGR TIME DELAY
EGR SPEED/TRANS
OSAC VAC BYPASS
ESC SPEED SWITCH
ESC ELfcC MODULE
EXHAUST MANIFOLD
RANK
115
116
40
55
56
59
60
62
63
117
8
67
61
29
122
71
13
123
118
120
119
72
78
82
52
HI.
CI
0.0
0.0
0.122E-03
0.357E-04
0.340E-04
0.227E-04
0.216E-04
0.187E-04
0.176E-04
0.0
0.290E-02
0.119E-04
0.204E-04
0.404E-03
0.0
0.851E-05
0.174E-02
0.0
0.0
0.0
0.0
0.851E-05
0.397E-05
0.284E-05
0.545E-04
___— _
RANK
96
98
77
103
131
97
113
111
108
99
5
109
118
17
105
110
6
106
100
102
101
120
125
122
47
LU
CI
c.o
c.o
c.o
0.0
0.0
0.0
0.0
0.0
0.0
0.0
C.562E-02
C.O
G.O
C.993E-03
0.0
0.0
0.337E-02
0.0
0.0
0.0
c.o
0.0
0.0
c.o
0.545E-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
CI
0.463E-02
0.211E-02
0.1226-02
0.715E-03
0.681E-03
0.454E-03
0.431E-03
0.374E-03
0.352E-03
0.306E-03
0.281E-03
0.238E-03
0.204E-03
0.199E-03
0.187E-03
0.170E-03
0.168E-03
0.159E-03
0.148E-03
0.148E-C3
0.125E-03
0.851E-04
0.794E-04
0.567E-04
0.545E-04
RANK
84
86
44
91
129
85
103
101
96
87
19
98
109
20
93
100
18
94
88
90
89
112
118
114
133
inu*
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.3
0.0
0.0
0.0
0.0
0.0
0.3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
CI
-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
CO
CRITICALITY INDEX RANKING - OEM SALES VOLUME
PRINCIPAL RANKING - SMOKE
LATE MODELS
PART PART
CODE NAME
5. 1. 1 VALVE LIFTER/SPR
5. 1. 4 VALVE SEALS
5. 1. 5 EXHAUST VALVES
3. 2. 0 AIR CLEANER ELEM
4. 5. 0 MFI VALVES
5. 1. 3 VALVE GUIDES
5. 2. 0 PISTON RINGS
5. 4. 1 HEAD GASKETS
4. 4. 0 FI THROTTLE VALV
5. 1. 2 VALVE CAM LOBES
4. 3. 0 FI PRES SENS/REG
3. 5. 0 SUPERCHARGER
6. 1. 4 PCV OIL SEPARATR
5. 5. 0 CAMSHAFTS
3. 4. 0 TURBOCHARGER
4. 8. 0 FI DIST MANIFOLD
4. 2. 0 FI HI PR£S PUMP
1. 1. 1 NEW GARB
1. 1. 2 REBUILT CARB
1. 1. 3 SPECIALTY CARB
1. 2. 1 IDLE STPSCLENOID
1. 2. 2 THROTTLE DASHPCT
1. 2. 3 THRTTL POSITIONR
1. 3. 1 METERING JETS
1. 3. 2 METERING RODS
RANK
20
27
28
44
107
53
54
70
106
85
88
74
76
99
86
97
100
13
8
29
21
39
48
45
42
HI,
CI
0.709E-03
0.411E-03
0.411E-03
0.106E-03
0.0
0.411E-04
0.411E-04
0.981E-05
0.0
0.210E-05
0.170E-05
0.567E-05
0.454E-05
0.284E-06
0.189E-05
0.420E-06
0.630E-07
0.174E-02
0.290E-02
0.404E-03
0.709E-03
0.132E-03
0.662E-04
0.103E-03
0.117E-03
W_»Mi
RANK
20
23
24
9
83
48
49
59
82
66
55
58
65
74
64
73
75
6
5
17
21
33
42
10
8
cu
CI
0.709E-03
C.411E-03
0.411E-03
0.211E-02
0.0
C.411E-04
0.411E-C4
C.981E-05
C.O
C.210E-05
0.170E-04
C.113E-04
0.34QE-C5
0.284E-06
0.3786-05
Q.315E-06
0.630E-07
0.337E-02
0.562E-02
0.993E-03
0.709E-03
C.132E-03
Q.662E-04
0.205E-02
0.235E-02
RANK
89
92
93
73
81
91
94
96
80
90
79
76
101
97
75
37
78
17
11
14
38
39
40
41
42
NUA
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
C.O
0.0
0.0
0.315E-06
0.0
C.168E-03
0.281E-03
0.199E-03
0.0
0.0
0.0
C.O
0.0
RANK
i
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
iHUIVC ----
CI
0.709E-02
0.411E-02
0.411E-02
0.704E-03
0.454E-03
0.411E-03
0.411E-03
0.981E-04
0.388E-04
0.210E-04
0.119E-04
0.397E-05
0.340E-05
0.284E-05
0.132E-05
0.315E-06
0.630E-07
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 - GARAGE SALES
PRINCIPAL RANKING - HC
LATE MODELS
PART
CODE
2.
2.
2.
2.
1.
1.
f 6.
- 1.
10 2.
2.
1.
2.
3.
5.
7.
1.
5.
5.
1.
2.
5.
5.
5.
7.
5.
5.
6.
3.
3.
3.
3.
1.
1.
4.
10.
1.
1.
2.
1.
3.
4.
1.
1.
1.
2.
2.
1.
4.
3.
1.
0
0
1
2
8
9
1
2
0
0
1
0
0
1
2
0
5
4
3
0
0
3
1
1
2
PART
NAPE
SPARK PLUGS
IGNITICN MIRES
CAP
ROTOR
REBUILDING KITS
FLOAT AND VALVE
PCV VALVE
REBUILT CARB
MAG/OPT TRIGGERS
El CONTROL CIRCT
NEW CARB
POINTS
AIR CLEANER ELEM
VALVE LIFTER/SPR
EXHAUST MANIFOLD
FUEL FILTER
EXHAUST VALVES
VALVE SEALS
SPECIALTY CARB
CONDENSER
PISTON RINGS
VALVE GUIDES
HEAD GASKETS
HIGH PERF EXHAST
VALVE CAM LOBES
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
Ml,
CI
0.266E+00
0.127E+00
0.168E-01
0.168E-01
0.950E-02
0.410E-02
0.295E-02
0.109E-02
0.447E-03
0.447E-03
0.388E-03
0.281E-03
0.244E-03
0.240E-03
0.215E-03
0.167E-03
0.159E-03
0.109E-03
0.881E-04
0.561E-04
0.278E-04
0.109E-04
0.224E-05
0.917E-06
0.721E-06
™^« »»
RANK
5
7
8
9
1
2
4
6
21
22
10
11
3
12
14
15
16
17
13
18
19
20
23
24
25
cu —
CI
0.266E-02
0.127E-02
0.842E-03
0.842E-03
0.475E-01
C.205E-01
0.295E-02
0.212E-02
0.447E-05
0.447E-05
0.750E-03
0.281E-03
C.487E-02
0.240E-03
0.215E-03
G.167E-03
0.159E-03
0.109E-03
0.217E-03
C.561E-04
0.278E-04
0.109E-04
0.224E-05
C.917E-06
0.721E-06
RANK
31
32
23
24
16
17
69
2
30
36
4
21
43
60
1
20
64
63
3
22
65
62
67
5
61
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.106E-03
0.0
C.O
0.375E-04
0.0
0.0
0.0
0.215E-C3
0.0
0.0
0.0
0.433E-04
C.O
0.0
0.0
0.0
0.917E-06
0.0
RANK
39
40
31
32
24
25
67
12
38
44
11
29
2
1
133
28
3
4
13
30
5
6
7
132
8
:>nu*t
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
0.162E-02
0.240E-02
0.0
0.0
0.159E-02
0.109E-02
0.0
0.0
0.278E-03
0.1096-03
0.224E-04
0.0
0.721E-05
-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
CRITICALITY INDEX RANKING - GARAGE SALES
PRINCIPAL RANKING - CO
LATE MODELS
PART
CODE
1. 3. 8
1. 3. 9
3. 2. 0
6. 1. 1
2. 5. 0
1. 1. 2
i 2. 6. 0
£ 2. 3. 1
2. 3. 2
1. 1. 1
2. 1. 0
5. 1. 1
1. 1. 3
7. 3. 2
1. 4. 0
5. 1. 5
5. 1. 4
2. 2. 0
5. 2. 0
5. 1. 3
2. 4. 0
2.10. 0
5. 4. 1
7. 3. 1
5. 1. 2
PART
NAME
REBUILDING KITS
FLOAT AND VALVE
AIR CLEANER ELEM
PCV VALVE
SPARK PLUGS
REBUILT GARB
IGNITICN WIRES
CAP
ROTOR
NEW CARB
POINTS
VALVE LIFTER/SPR
SPECIALTY CARB
EXHAUST MANIFOLD
FUEL FILTER
EXHAUST VALVES
VALVE SEALS
CONDENSER
PISTON RINGS
VALVE GUIDES
MAG/OPT TRIGGERS
El CONTROL CIRCT
HEAD GASKETS
HIGH PERF EXHAST
VALVE CAM LOBES
RANK
5
6
13
7
1
8
2
3
4
11
12
14
19
15
16
17
18
20
21
22
9
10
23
24
25
nu — — —
CI
0.950E-02
0.410E-02
0.244E-03
0.295E-02
0.266E+00
0.109E-02
0.127E+00
0.168E-01
0.168E-01
0.388E-03
0.281E-03
0.240E-03
0.881E-04
0.215E-03
0.167E-03
0.159E-03
0.109E-03
0.561E-04
0.278E-04
0.109E-04
0.447E-03
0.447E-03
0.224E-05
0.917E-06
0.721E-06
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
uu — —
CI
0.475E-01
C.205E-01
C.487E-02
0.295E-02
0.266E-C2
0.212E-02
0.127E-02
0.842E-03
G.842E-03
0.750E-03
0.281E-C3
0.240E-03
0.217E-03
0.215E-03
C.167E-03
0.159E-03
0.1C9E-03
0.561E-04
C.278E-04
C.109E-G4
0.447E-05
0.447E-05
C.224E-05
C.917E-06
0.721E-06
RANK
16
17
43
69
31
2
32
23
24
4
21
60
3
1
20
64
63
22
65
62
30
36
67
5
61
niUA — — — — —
CI
0.0
0.0
0.0
0.0
0.0
0.106E-03
0.0
0.0
0.0
0.375E-04
0.0
0.0
0.433E-04
3.215E-03
C.O
C.O
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.917E-06
0.0
RANK
24
25
2
67
39
12
40
31
32
11
29
1
13
133
28
3
4
30
5
6
38
44
7
132
8
anui\c — — — —
CI
0.0
0.0
0.162E-02
0.0
0.0
0.0
0.0
0.0
0.0
6.0
0.0
0.240E-02
0.0
0.0
0.0
0.159E-02
0.109E-02
0.0
0.278E-03
0.109E-03
0.0
0.0
0.224E-04
0.0
0.721E-05
-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
CRITICALITY INDEX RANKING - GARAGE SALES
PRINCIPAL RANKING - NOX
LATE MODELS
PART
CODE
7. 3. 2
1. 1. 2
1. 1. 3
1. 1. 1
7. 3. 1
> 1. 2. 1
^ 1. 2. 2
^ 1. 2. 3
1. 3. 1
1. 3. 2
1. 3. 3
1. 3. 4
1. 3. 5
1. 3. 6
1. 3. 7
1. 3. 8
1. 3. 9
1. 3.10
1. 3.11
1. 4. 0
2. 1. 0
2. 2. 0
2. 3. 1
2. 3. 2
2. 3. 3
PART
NAME
EXHAUST MANIFOLD
REBUILT CARB
SPECIALTY CARB
NEW CARB
HIGH PERF EXHAST
IDLE STPSCLENOID
THROTTLE DASHPCT
THRTTL POSITIONR
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
MECH ADVANCE
RANK
15
8
19
11
24
28
29
30
31
32
33
34
35
36
37
5
6
38
39
16
12
20
3
4
40
ni.
CI
0.215E-03
0.109E-02
0.881E-04
0.388E-03
0.917E-06
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.950E-02
0.410E-02
0.0
0.0
0.167E-03
0.281E-03
0.561E-04
0.168E-01
0.168E-01
0.0
• *•••
RANK
14
6
13
10
24
28
29
30
31
32
33
34
35
36
37
1
2
38
39
15
11
18
8
9
40
CI
0.215E-03
C.212E-02
0.217E-03
0.750E-03
0.917E-06
0.0
0.0
C.O
0.0
0.0
C.O
0.0
0.0
0.0
C.O
0.475E-01
C.205fc-01
C.O
0.0
C.167E-03
C.261E-03
C.561E-C4
C.842E-03
C.842E-03
C.O
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
CI
0.215E-03
0.106E-03
0.433E-04
0.375E-04
0.917E-06
C.O
G.O
0.0
0.0
0.0
0.0
0.0
C.O
n.o
0.0
0.0
0.0
C.O
0.0
0.0
0.0
0.0
0.0
0.0
0.0
RANK
133
12
13
11
132
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
anuiv
0.0
0.0
0.0
0.0
0.0
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.c
0.0
0.0
0.0
0.0
0.0
0.0
0.0
CI
-------
PART
CODE
5. 1. 1
3. 2. 0
5. 1. 5
4
0
5. 1.
5. 2.
5. 1. 3
5. 4. 1
5. 1. 2
5. 5. 0
4. 2. 0
1. 1. 1
1. 1. 2
1. 1. 3
1. 2. 1
1. 2. 2
1. 2. 3
1. 3. 1
1. 3. 2
1. 3. 3
1. 3. 4
1. 3. 5
1. 3. 6
1. 3. 7
1. 3. 8
1. 3. 9
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
CRITICALITY INDEX RANKING - GARAGE SALES
PRINCIPAL RANKING - SMOKE
LATE MODELS
PART
NAME
VALVE LIFTER/SPR
AIR CLEANER ELEM
EXHAUST VALVES
VALVE SEALS
PISTON RINGS
VALVE GUIDES
HEAD GASKETS
VALVE CAM LOBES
CAMSHAFTS
FI HI PRES PUMP
NEW GARB
REBUILT CARB
SPECIALTY CARB
IDLE STPSCLENOID
THROTTLE DASHPOT
THHTTL PCSITIONR
METERING JETS
METERING RODS
VAC BRK VALVE
CHCKE MECHANISM
ACCELERATOR PUMP
POWER VALVES
GASKETS
REBUILDING KITS
FLOAT AND VALVE
RANK
14
13
17
18
21
22
23
25
26
27
11
8
19
28
29
30
31
32
33
34
35
36
37
5
6
ML
CI
0.240E-03
0.244E-03
0.159E-03
0.109E-03
0.278E-04
0.109E-04
0.224E-05
0.721E-06
0.721E-06
0.101E-07
0.388E-03
0.109E-02
0.881E-04
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.950E-02
0.410E-02
RANK
12
3
16
17
19
20
23
25
26
27
10
6
13
28
29
30
31
32
33
34
35
36
37
1
2
CI
C.240E-03
0.487E-02
0.159E-03
C.109E-03
G.278E-04
C.109E-04
0.224E-05
C.721E-C6
C.721E-06
C.101E-07
0.750E-03
0.212E-02
0.217E-03
G.O
C.O
C.O
0,0
0.0
0.0
0.0
0.0
C.O
0.0
0.475E-01
0.205E-01
RANK
60
43
64
63
65
62
67
61
68
48
4
2
3
6
7
8
9
10
11
12
13
14
15
16
17
IMUA — — —
CI
0.0
0.0
C.O
0.0
C.O
0.0
0.0
C.O
0.0
0.0
0.375E-04
Q.106E-Q3
0.433E-04
0.0
C.O
G.O
0.0
0.0
C.O
0.0
0.0
0.0
0.0
o.o
0.0
RANK
i
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
CI
0.240E-02
0.162E-02
0.159E-02
0.109E-02
0.278E-03
0.109E-03
0.224E-04
0.721E-05
0.7216-05
0.101E-07
0.0
0.0
0.0
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 - WAREHOUSE SALES
PRINCIPAL RANKING - HC
LATE MODELS
PART
CODE
2.
2.
1.
1.
2.
2.
f l-
ro 1.
00 A
o .
1.
1.
6.
6.
3.
1.
3.
5.
3.
1.
6.
3.
2.
2.
6.
1.
5.
6.
3.
1.
3.
3.
3.
1.
1.
1.
3.
10.
1.
1.
2.
1.
1.
1.
2.
3.
2.
3.
1.
10.
4.
0
0
8
2
2
1
4
1
1
3
3
1
3
3
1
4
1
1
2
2
0
7
0
4
0
PART
NAME
SPARK PLUGS
IGNITION WIRES
REBUILDING KITS
REBUILT GARB
ROTOR
CAP
CHOKE MECHANISM
NEW CARB
PCV VALVE
SPECIALTY CARB
VAC BRK VALVE
HEAT RISER
PCV FRSHAIR FLTR
TAC VAC MCTOR
IDLE STPSCLENOID
TAC VAC HOSES
VALVE LIFTER/SPR
TAC SHROUD
THROTTLE OASHPOT
AI HOSES
AIR CLEANER ELEM
SPARK DELAY VLV
POINTS
DECEL VALVE
FUEL FILTER
RANK
1
2
3
^
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
nu — —
CI
0.446E+00
0.340E-01
0.169E-01
0.608E-02
0.539E-02
0.459E-02
0.384E-02
0.379E-02
0.161E-02
0.870E-03
0.787E-03
0.663E-03
0.495E-03
0.441E-03
0.407E-03
0.374E-03
0.272E-03
0.235E-03
0.210E-03
0.200E-03
0.155E-03
0.148E-03
0.146E-03
0.133E-03
0.105E-03
RANK
5
13
1
3
15
17
2
4
8
7
9
25
11
26
12
29
14
59
18
10
6
56
19
20
22
uu
CI
C.446E-Q2
0.340E-03
C.846E-01
C.118E-01
0.269E-03
0.229E-C3
0.192E-01
0.733E-02
0.161E-02
0.214E-02
0.787E-03
C.663E-04
0.495E-03
0.441t-04
0.407E-03
0.374E-04
0.272E-03
0.0
0.21Ce-C3
0.500E-03
Q.310E-02
C.O
Q.146E-03
0.133E-03
C.105E-03
RANK
36
37
23
4
31
30
19
6
74
5
18
126
76
45
13
46
65
43
14
85
48
2
28
129
27
NUX
CI
0.0
C.O
0.0
0.5B9E-03
0.0
0.0
C.O
0.367E-03
0.0
0.428E-03
0.0
0.0
0.0
0.0
C.O
0.0
0.0
C.O
C.O
0.0
C.O
0.148E-G2
C.O
0.0
0.0
RANK
40
41
25
13
33
32
21
12
67
14
20
123
69
49
15
50
1
47
16
78
2
38
30
126
29
5HUKt
CI
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.272E-02
0.0
0.0
0.0
0.103E-02
0.0
0.0
0.0
0.0
-------
I
ro
PART
CODE
1.
1.
1.
1.
2.
3.
I.
6.
1.
6.
6.
1.
2.
5.
2.
2.
2.
1.
2.
6.
6.
1.
5.
5.
6.
3.
3.
1.
1.
5.
2.
1.
1.
3.
3.
1.
2.
6.
1.
3.
3.
3.
2.
i.
10.
3.
4.
1.
1.
10.
8
4
2
1
0
0
3
1
3
2
3
1
0
1
2
4
1
2
0
4
5
0
4
5
1
AUTCMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
CRITICALITY INDEX RANKING - WAREHOUSE SALES
PRINCIPAL RANKING - CO
LATE MODELS
PART
NAME
REBUILDING KITS
CHCKE MECHANISM
REBUILT CARB
NEW CARB
SPARK PLUGS
AIR CLEANER ELEM
SPECIALTY CARB
PCV VALVE
VAC bRK VALVE
AI HOSES
PCV FRSHAIR FLTR
IDLE STPSCLENOIO
IGNITION HIRES
VALVE LIFTER/SPR
ROTOR
VACUUM ADVANCE
CAP
THROTTLE DASHPOT
POINTS
DECEL VALVE
AI BYPASS/DVRTR
FUEL FILTER
VALVE SEALS
EXHAUST VALVES
HEAT RISER
RANK
3
7
4
8
1
21
10
9
11
20
13
15
2
17
5
62
6
19
23
24
32
25
28
29
12
in.
CI
0.169E-01
0.384E-02
0.608E-02
0.379E-02
0.446E+00
0.155E-03
0.870E-03
0.161E-02
0.787E-03
0.200E-03
0.495E-03
0.407E-03
0.340E-01
0.272E-03
0.539E-02
0.0
0.459E-02
0.210E-03
0.146E-03
0.133E-03
0.430E-04
0.105E-03
0.919E-04
0.919E-04
0.663E-03
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
uu —
CI
0.846E-01
G.192E-C1
0.118E-01
0.733E-02
G.446E-02
0.310E-02
0.214E-02
C.161E-02
0.787E-03 .
0.500E-03
0.495E-03
0.407E-03
0.340E-03
0.272E-03
Q.269E-03
C.251E-03
0.229E-03
0.210E-03
0.146E-03
0.133E-03
0.108E-03
0.105E-03
0.919E-04
0.919E-04
C.663E-04
RANK
23
19
4
6
36
48
5
74
18
85
76
13
37
65
31
32
30
14
28
129
88
27
68
69
126
CI
0.0
0.0
0.589E-03
0.367E-03
0.0
C.O
0.428E-03
0.0
0.0
0.0
o.o
0.0
0.0
0.0
o.o
0.0
0.0
o.o
0.0
0.0
0.0
C.O
0.0
0.0
0.0
RANK
25
21
13
12
40
2
14
67
20
78
69
15
41
1
33
35
32
16
30
126
81
29
3
4
123
inuisc — —
CI
0.0
0.0
0.0
0.0
0.0
0.103E-02
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.272E-02
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.919E-03
0.919E-03
0.0
-------
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
PART
CODE
6.10. 7
2. 3. 7
6. 4. 1
1. 1. 2
1. 1. 3
1. 1. 1
> 6. 4. 8
ro 6. 5. 1
01 6. 5. 8
2. 3. 3
7. 3. 2
7. 3. 1
1. 2. 1
1. 2. 2
1. 2. 3
1. 3. 1
1. 3. 2
1. 3. 3
1. 3. 4
1. 3. 5
1. 3. 6
1. 3. 7
1. 3. 8
1. 3. 9
1. 3.10
CRITICALITY INDEX RANKING - WAREHOUSE SALES
PRINCIPAL RANKING - NOX
LATE MODELS
PART
NAME
THERMO VAC VALV
SPARK DELAY VLV
EGR VALVES
REBUILT CARB
SPECIALTY CARB
NE* CARB
EGR VAC AMP
TCS VAC SOLENOID
TCS TEMP SWITCH
MECH ADVANCE
EXHAUST MANIFOLD
HIGH PERF EXHAST
IDLE STPSCLENOID
THROTTLE OASHPOT
THRTTL POSITICNR
METERING JETS
METERING RODS
VAC BHK VALVE
CHCKE MECHANISM
ACCELERATOR PUMP
POWER VALVES
GASKETS
REBUILDING KITS
FLOAT AND VALVE
IDLE ADJUSTMENT
RANK
30
22
92
4
10
8
36
42
43
46
49
52
15
19
53
54
55
11
7
56
57
58
3
59
60
nv, — —
CI
0.882E-04
0.148E-03
0.0
0.608E-02
0.870E-03
0.379E-02
0.132E-04
0.826E-05
0.779E-05
0.588E-05
0.490E-06
0.647E-07
0.407E-03
0.210E-03
0.0
0.0
0.0
0.787E-03
0.384E-02
0.0
0.0
0.0
0.169E-01
0.3
0.0
RANK
131
56
88
3
7
4
95
100
107
37
41
45
12
18
46
47
48
9
2
49
50
51
1
52
53
CI
0.0
C.O
C.O
C.118E-01
C.214E-02
Q.733E-02
C.O
0.0
0.0
C.568E-05
C.490E-06
C.647E-07
0.407E-03
C.210E-03
C.O
0.0
0.0
C.787E-03
C.192E-01
C.O
C.O
0.0
0.846E-01
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
CI
0.176E-02
0.148E-02
0.928E-03
0.589E-03
0.428E-03
0.367E-03
0.265E-03
0.165E-03
3.156E-03
0.588E-04
0.490E-06
0.647E-07
0.0
0.0
0.0
0.0
0.0
C.O
3.0
0.0
0.0
0.0
0.0
0.0
C.O
RANK
129
38
84
13
14
12
91
96
103
34
133
132
15
16
17
18
19
20
21
22
23
24
25
26
27
:>nu*
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
CI
-------
PART
CODE
5. 1. 1
3. 2. 0
5. 1. 4
5. 1. 5
4. 4. 0
3> 5. 1. 3
^ 5. 4. 1
en 5* 2. 0
5. 5. 0
5. 1. 2
4. 2. 0
1. 1. 1
1. 1. 2
1. 1. 3
1. 2. 1
1. 2. 2
1. 2. 3
1. 3. 1
1. 3. 2
1. 3. 3
1. 3. 4
1. 3. 5
1. 3. 6
1. 3. 7
1. 3. 8
AUTOMOTIVE PARTS STUDY - EPA CONTRACT NO. 68-01-1957
CRITICALITY INDEX RANKING - WAREHOUSE SALES
PRINCIPAL RANKING - SMOKE
LATE MODELS
PART
NAME
VALVE LIFTER/SPR
AIR CLEANER ELEM
VALVE SEALS
EXHAUST VALVES
FI THROTTLE VALV
VALVE GUIDES
HEAD GASKETS
PISTON RINGS
CAMSHAFTS
VALVE CAM LOBES
FI HI PRES PUMP
NEW CARB
REBUILT CARB
SPECIALTY CARB
IDLE STPSCLENQID
THROTTLE DASHPOT
THRTTL POSITIONR
METERING JETS
METERING RODS
VAC BRK VALVE
CHOKE MECHANISM
ACCELERATOR PUMP
POWER VALVES
GASKETS
REBUILDING KITS
RANK
17
21
28
29
70
38
39
40
41
48
51
8
4
10
15
19
53
54
55
11
7
56
57
58
3
HC
CI
0.272E-03
0.155E-03
0.919E-04
0.919E-04
0.0
0.919E-05
0.910E-05
0.901E-05
0.901E-05
0.500E-06
0.183E-06
0.379E-02
0.608E-02
0.870E-03
0.407E-03
0.210E-03
0.0
0.0
0.0
0.787E-03
0.384E-02
0.0
0.0
0.0
0.169E-01
RANK
14
6
23
24
65
32
33
34
35
40
43
4
3
7
12
18
46
47
48
9
2
49
50
51
1
^u
CI
0.272E-C3
0.310E-02
C.919E-04
0.919E-04
c.o
0.919E-05
G.91CE-05
0.9C1E-05
0.901E-05
0.500E-06
C.183E-06
0.733E-02
0.118E-01
C.214E-02
C.407E-03
0.210E-03
C.O
0.0
C.O
0.787E-03
0.192E-01
0.0
0.0
0.0
C.846E-01
RANK
65
48
68
69
55
67
72
70
73
66
53
6
4
5
13
14
15
16
17
18
19
20
21
22
23
CI
0.0
0.0
0.0
3.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.367E-03
C.589E-03
0.428E-03
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
onu»vc — -— —
CI
0.272E-02
0.1D3E-02
0.919E-03
0.919E-03
0.241E-03
0.919E-04
0.910E-04
0.901E-04
0.901E-04
0.500E-05
0.183E-06
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
-------
Appendix B
CRITICALITY INDEX INPUT PARAMETER VALUES
-------
PART
NAME
NEW CARB
REBUILT CARB
SPECIALTY CARB
IDLE STPSOLENOIO
THROTTLE OASHPOT
THRTTL PGSITICNR
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
MECH ADVANCE
VACUUM ADVANCE
DISTRIBUTOR DRIV
DUAL DIAPHI* DIST
SPARK DELAY VLV
MAG/OPT TRIGGERS
SPARK PLUGS
IGNITION HIRES
COIL
CAPACITIVE OISCH
BALLAST RESISTOR
El CONTROL CIRCT
IGN TIMING ADJ
TAC SHROLD
JASCLI
— PRE-1975 —
EVAP
0.1
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
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
3.0
0.0
0.0
0.0
HC
1.0
1.0
1.0
0.1
0.1
0.1
0.1
0.1
0.1
2.0
C.I
2.0
0.1
2.0
2.0
0.0
0.1
0.1
1.0
1.0
2.0
2.0
0.1
0.0
1.0
0.0
0.1
10.0
10.0
10.0
1.0
1.0
1.0
10.0
0.0
0.1
CO
2.0
2.0
2.0
1.0
1.0
1.0
2.0
2.0
1.0
10.0
2.0
10.0
0.0
10. 0
10.0
0.0
1.0
0.0
0.0
0.0
0.0
0.0
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
NCX
0.1
0.1
1.0
0.0
0.0
o.c
O.J
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
9.0
0.0
1.0
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
EMISS
ION INCREASE
— POST-1975 ~
HC
1.0
1.0
2.0
1.0
1.0
1.0
0.1
3.1
1.0
2.3
0.1
2.0
0.1
2.0
2.0
0.0
1.0
0.1
0.1
0.1
2.0
2.0
O.I
0.0
0.1
0.0
0.1
10.0
10.0
10.0
0.1
0.1
0.1
10.0
0.0
1.3
CO
2.0
2.0
5.0
1.0
1.0
1.0
2.3
2.0
1.0
10.0
2.0
10.0
0.1
10.0
10.0
0.0
1.0
0.1
0.1
0.1
0.1
3.1
0.1
1.0
0.1
1.0
0.0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.0
0.0
NOX
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
0.0
0.0
0.0
0.0
0.0
0.0
1.0
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
FACTOR
s
- DIESEL (SMOKE) -
PRE-1974
ACCEL
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
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
3.0
POST-1974 —
ACCEL
0.0
0.0
0.0
0.0
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.c
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
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
c.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
c.o
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
PROBABILITY
FACTORS SALES VOLUME
EARLY
FAIL
0.30
0.50
0.70
0.30
0.30
0.30
0.10
0.30
0.30
0.30
0.30
0.30
0.10
0.70
0.30
0.0
0.10
0.10
0.50
0.10
0.30
0.30
0.30
0.30
0.10
0.30
0.50
0.10
0.70
0.30
0.10
0.10
0.10
0.10
0.0
0.10
NO FACTORS
REPL OEM GARAGE WAREHOUSE
0.90 0.0062 0.0014 0.0136
0.90 0.0062 0.0024 0.0131
0.90 0.0003 0.0001 0.0007
0.50 0.0047 0.0 0.0027
0.50 0.0009 0.0 0.0014
0.50 0.0004 0.0 0.0
0.90 0.0114 0.0 0.0
0.90 0.0043 0.0 0.0
0.90 0.0063 0.0 0.0029
0.90 0.0062 0.0 0.0071
0.90 0.0062 0.0 0.0
0.90 0.0062 0.0 0.0
0.90 0.0062 0.0 0.0
0.90 0.0062 0.0075 0.0134
0.90 0.0062 0.0076 0.0
0.0 0.0 0.0 0.0
0.90 0.0002 0.0 0.0
0.50 0.0240 0.0333 0.0211
0.10 0.0146 0.0561 0.0293
0.10 0.0043 0.0561 0.0293
0.50 0.0062 0.0561 0.0153
0.50 0.0062 0.0561 0.0180
0.50 0.0003 0.0 '0.0004
0.50 0.0062 0.0 0.0017
0.50 0.0062 0.0 0.0021
0.90 0.0003 0.0 0.0
0.90 0.0027 0.0 C.0033
0.10 0.0020 0.0045 0.0001
0.10 0.2700 0.3802 0.6374
0.50 0.0451 0.0849 0.0226
0.90 0.0062 0.0 0.0047
0.10 0.0003 0.0 0.0002
0.90 0.0062 0.0 0.0
0.10 0.0020 0.0045 0.0006
0.0 0.0062 0.0158 0.0
0.90 0.0061 0.0 0.0026
-------
PART
NAME
TAG THERMOSTAT
TAG VAC MOTOR
TAG VAC HOSES
TAG FRESH AIR IN
AIR CLEANER ELEM
INTAKE MANIFOLD
TURBCCHARGER
SUPERCHARGER
MFI ACCUMULATOR
FI HI PRES PUMP
FI PRES SENS/REG
FI THROTTLE VALV
MFI VALVES
EF1 AIR SENS/SWH
EFI TEMPSENS/SHH
FI OIST MANIFOLD
EFI INJECTORS
EFI TRIGGER SUCH
EFI CONTROL CIRC
FI STARTING VALV
FI IDLE ADJUST
VALVE LIFTER/SPR
VALVE CAM LOBES
VALVE GUIDES
VALVE SEALS
EXHAUST VALVES
PISTON RINGS
PISTON/RODS
HEAD GASKETS
CAMSHAFTS
PCV VALVE
PCV HOSES
PCV FRSHAIR FLTR
PCV OIL SEPARATR
EVAP CANISTER
EVAP HOSES
JASCLIf
— PRE-1975 —
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
0.1
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
10.0
0.0
0.1
10.0
10.0
HC
0.1
0.1
0.1
0.1
0.1
0.1
1.0
1.0
0.0
0.1
0.1
0.0
0.0
1.0
1.0
0.1
0.1
2.0
0.1
1.0
0.1
1.0
1.0
1.0
1.0
1.0
1.0
0.1
1.0
1.0
0.1
0.1
0.1
1.0
0.0
0.1
cc
0.0
0.0
0.0
0.1
2.0
0.1
2.0
2.0
0.0
0.1
1.0
0.0
0.0
5.0
5.0
0.1
2.0
0.1
0.1
5.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.1
1.0
1.0
1.0
0.0
1.0
1.0
0.0
0.0
NOX
0.0
0.0
0.0
0.0
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
0.1
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
EMISSION INCREASE
"t t
— POST-1975 —
HC
1.0
1.3
1.0
0.1
0.1
0.1
1.0
1.0
0.0
0.1
0.1
0.0
0.0
1.3
1.3
0.1
0.1
2.3
0.1
1.0
1.0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
1.3
0.1
1.0
0.1
0.0
0.1
CO
0.0
0.1
0.1
0.1
2.0
0.1
2.0
2.0
0.0
0.1
1.0
0.0
0.0
5.0
5.0
0.1
2.0
1.0
0.1
5.0
1.0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
1.0
0.1
1.0
0.1
0.0
0.1
NOX
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
0.1
0.0
0.1
0.1
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
FACTOR
s
- DIESEL (SMOKE) -
PRE-1974
ACCEL
0.0
0.0
0.0
0.0
1.0
0.0
1.0
1.0
0.1
0.1
1.0
1.0
1.0
0.0
0.0
0.1
0.0
0.0
0.1
0.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.1
1.0
1.0
0.0
0.0
0.0
0.1
0.0
0.0
LUG
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.1
0.1
0.1
0.1
1.0
0.0
0.0
0.1
0.0
0.0
0.1
0.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.1
1.0
1.0
0.0
0.0
0.0
0.1
0.0
0.0
POST-1974 —
ACCEL
0.0
0.0
0.0
0.0
1.0
0.0
1.0
1.0
0.1
0.1
1.0
2.0
1.0
0.0
0.0
0.1
0.0
0.0
0.1
0.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.1
1.0
1.0
0.0
0.0
0.0
0.1
0.0
0.0
LUG
0.0
0.0
0.0
0.0
0.0
G.O
0.1
0.1
0.1
0.1
0.1
O.I
1.0
0.0
0.0
0.1
o.c
0.0
0.1
0.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.1
1.0
1.0
0.0
0.0
0.0
0.1
0.0
0.0
PEAK
0.0
0.0
0.0
0.0
1.0
0.0
1.0
1.0
0.1
0.1
1.0
2.0
1.0
0.0
0.0
0.1
0.0
0.0
0.1
0.0
2.0
1.0
1.0
1.0
1.0
1.0
1.0
0.1
1.0
1.0
0.0
0.0
0.0
0.1
0.0
0.0
PROBABILITY
FACTORS SALES VOLUME
EARLY
FAIL
0.10
0.30
0.30
0.30
0.10
0.50
0.10
0.30
0.01
0.10
0.30
0.50
2.00
0.30
0.30
0.10
0.50
0.30
0.10
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
0.30
0.30
0.10
NO FACTORS
REPL OEM GARAGE WAREHOUSE
0.90 0.0061 0.0 0.0011
0.90 0.0052 0.0 0.0016
0.90 0.0052 0.0 0.0014
0.90 0.0001 0.0 0.0001
0.50 0.0211 0.0487 0.0310
0.90 0.0003 0.0 0.0001
0.30 0.0001 0.0 0.0
0.30 0.0001 0.0 0.0
0.90 0.0 0.0 0.0
0.10 0.0001 0.0000 0.0002
0.90 0.0001 0.0 0.0
0.90 0.0001 0.0 0.0004
0.90 0.0003 0.0 0.0
0.10 0.0 0.0 0.0
0.90 0.0 0.0 0.0
0.50 0.0001 0.0 0.0
0.90 0.0001 0.0 0.0
0.10 0.0 0.0 0.0
0.10 0.0 0.0 0.0
0.90 0.0001 0.0 0.0
0.30 0.0 0.0 0.0
0.50 0.0473 0.0160 0.0181
0.90 0.0023 0.0008 0.0006
0.90 0.0457 0.0122 0.0102
0.90 0.0457 0.0122 0.0102
0.90 0.0457 0.0177 0.0102
0.90 0.0457 0.0309 0.0100
0.10 0.0457 0.0 0.0029
0.90 0.0109 0.0025 0.0101
0.90 0.0003 0.0008 0.0100
0.30 0.0216 0.0328 0.0179
0.50 0.0062 0.0 0.0
0.70 0.0154 0.0 0.0071
0.90 0.0001 0.0 0.0
0.50 0.0064 0.0 0.0
0.50 0.0062 0.0 0.0
-------
PART
NAME
EVAP FRSH AIR
EVAP VPRL1G SEP
EVAP VAPOR CONTR
FUEL TANK/CAP
AI MANIFOLD
AI HOSES
AI AIR FILTER
AI CHECKVALVES
AI BYPASS/DVRTR
AI GULP VALVES
AI PUMP/BELTS
EGR VALVES
EGR HOSES/SEALS
EGR THERMO VALVE
EGR SOLENOID VLV
EGR TEMP SWITCH
EGR SPEED/TRANS
EGR TIME DELAY
EGR VAC AMP
EGR VAC REUUCER
EGR CARB SPACER
EGR BACKPRES SEN
EGR CHECKVALVE
TCS VAC SOLENOID
TCS VAC HOSES
TCS TIME DELAY
TCS CEC VALVE
TCS THERMO VALVE
TCS TRANS SWITCH
TCS REVERSE RELY
TCS TEMP SWITCH
SCS VACUUM SOLEN
SCS VACUM LINE
SCS TIME DELAY
SCS SPEED SWITCH
SCS THERMO VALVE
iASCLU
— PRE-1975 —
EVAP
2.0
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
G.O
0.0
0.0
3.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
c.o
0.0
HC
0.0
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
0.1
0.1
C.I
2.0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
CO
c.o
c.o
0.0
c.o
1.0
1.0
0.1
0.1
0.1
0.1
1.0
G.O
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.3
0.0
0.0
0.3
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
NOX
0.0
0.0
0.0
0.0
0.0
3.0
0.0
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
3.0
2.0
2.0
2.0
2.0
2.0
3.0
2.0
2.0
2.0
EMISSION INCREASE
— POST-1975 —
HC
0.0
0.3
0.0
0.3
2.0
2.3
1.0
1.3
2.0
2.0
2.0
3.0
0.1
0.0
0.0
0.0
0.0
3.0
0.1
0.0
0.0
0.0
0.3
3.1
0.1
3.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
CO
0.0
0.0
0.0
3.0
5.0
5.0
1.0
1.0
5.0
5.0
5.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.3
1.3
0.0
0.1
0.0
0.0
0.0
0.0
0.0
1.0
0.0
0.0
0.0
NOX
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
o.o
0.0
0.0
2.C
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
FACTOR
s
- DIESEL (SMOKE)
PRE-1974
ACCEL
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
C.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
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
0.3
0.0
0.0
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-1974 —
ACCEL
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
LUG
0.0
0.0
0.0
0.0
0.0
c.c
o.c
0.0
0.0
0.0
o.c
0.0
0.0
0.0
c.o
0.0
0.0
o.o
c.o
0.0
0.0
c.o
0.0
0.0
0.0
0.0
c.o
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
o.c
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
0.3
0.0
0.0
0.0
0.0
0.0
0.0
PROBABILITY
FACTORS SALES VOLUME
EARLY
FAIL
0.10
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
NO FACTORS
REPL OEM GARAGE
0.50 0.0171 0.0
0.90 0.0061 0.0
0.90 0.0031 0.0
0.90 0.0062 0.0
0.90 O.C061 0.0
0.70 0.0032 0.0
0.70 0.0032 0.0
0.50 0.0053 0.0
0.50 0.0032 0.0
0.50 0.0 0.0
0.73 0.0032 0.0
0.70 0.0047 0.0
0.50 0.0045 0.0
0.90 0.0039 0.0
0.90 0.0017 0.0
0.90 0.0008 0.0
0.90 0.0007 3.0
0.90 O.C008 0.0
0.90 0.0013 0.0
0.90 0.0001 0.0
0.90 0.0007 0.0
0.90 0.0003 0.0
0.90 0.0001 0.0
0.90 0.0020 0.0
0.50 0.0021 0.0
0.90 0.0013 0.0
0.90 0.0001 0.0
0.90 0.0003 0.0
0.90 0.0021 0.0
0.90 0.0 0.0
0.90 0.0024 0.0
0.90 0.0001 0.0
0.50 0.0001 0.0
0.90 0.0 0.0
0.90 0.0001 0.0
0.90 0.0001 0.0
WAREHOUSE
0.0030
0.0
0.0
0.0
0.0
0.0014
0.0
0.0
0.0004
0.0
0.0001
0.0009
0.0
0.0
0.0
0.0
0.0
0.0
0.0005
0.0
0.0
0.0
0.0
0.0009
0.0
0.0
0.0
0.0
0.0
0.0
0.0009
0.0
0.0
0.0
0.0
0.0
-------
EMISSION INCREASE FACTORS
PROBABILITY
PART
NAME
OSAC VAC ORIFICE
OSAC VAC HOSES
OSAC THERMO VALV
OSAC VAC BYPASS
OSAC TEMP SENSOR
ESC ELEC MODULE
ESC HOSES
ESC VAC VALVES
ESC TEMP SWITCH
ESC SPEED SWITCH
CAT BODY
CAT ACTIVE MEDIA
CAT INERTMEDIA
CAT SHELL
HEAT RISER
ELEC ASSIST CHKE
STAGED PULLDOWN
DECEL VALVE
DIST VACDECL VLV
DIST START SOLEN
THERMO VAC VALV
COOLING THERPST
ELECTRICAL SYSTM
HIGH PERF EXHAST
EXHAUST MANIFOLD
DISTR VACUUM VLV
OAiULU
— PRE-1975 ~
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
c.o
0.0
0.0
0.0
0.0
0.0
0.0
HC
0.1
0.1
0.1
0.1
0.1
0.1
0.1
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
0.1
0.1
0.1
CO
0.0
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
0.1
0.1
0.0
NOX
1.0
0.0
1.0
1.0
1.0
2.0
0.0
2.0
2.0
2.0
0.0
3.0
0.0
0.0
0.0
0.0
0.0
0.0
2.0
0.0
2.0
0.0
0.0
0.1
0.1
0.1
Mt
— POST-1975 —
HC
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.0
0.0
0.0
0.0
1.0
0.1
0.1
1.0
0.1
1.0
0.1
0.0
0.0
0.1
0.1
C.I
CO
0.0
1.0
0.0
0.0
0.0
0.0
1.0
o.c
0.0
0.0
0.0
0.0
0.0
0.0
0.1
1.0
1.0
1.0
0.0
1.0
0.0
0.0
0.0
0.1
0.1
0.0
NOX
1.0
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
0.1
0.1
0.1
uie
PRE-1974
ACCEL
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
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
atHinuM:)
POST-1974 —
ACCEL
0.0
0.0
0.0
O.C
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
LUG
0.0
0.0
0.0
0.0
0,0
0.0
c.o
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
c.o
0.0
0.0
0.0
0.0
0.0
0.0
0.0
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
l-Al 1
EARLY
FAIL
0.30
0.10
0.30
0.30
0.10
0.10
0.10
0.10
0.10
0.10
0.0
0.0
0.0
0.0
0.70
0.10
0.30
0.30
0.30
0.10
0.30
0.0
0.0
0.10
0.10
0.30
UKJ> iALCi VULUnC
NO FACTORS
REPL OEM GARAGE MAREHOI
0.90 0.0008 0.0 0.0
0.50 0.0008 0.0 0.0
0.90 0.0 0.0 0.0
0.90 0.0003 0.0 0.0
0.90 0.0003 0.0 0.0
0.90 0.0003 0.0 0.0
0.50 0.0003 0.0 0.0
0.90 0.0003 0.0 0.0
0.90 0.0003 0.0 0.0
0.90 0.0004 0.0 0.0
0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0
0.0 0.0 0.0 0.0
0.90 0.0038 0.0 0.0011
0.90 0.0018 0.0 0.0
0.90 0.0004 0.0 0.0
0.90 0.0003 0.0 0.0005
0.90 0.0001 0.0 0.0
0.50 0.0001 0.0 0.0
0.90 0.0013 0.0 0.0033
0.0 0.0064 0.0148 0.0
0.0 0.0063 0.0 0.0
0.10 0.0006 0.0009 0.0001
0.50 0.0109 0.0431 0.0001
0.90 0.0 0.0 0.0
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
340/2-76-002
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Effect of Automotive Parts on Vehicle and Engine
Emissions
Phase II - After-Market Parts
5. REPORT DATE
March 1877
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Richard R. Carlson
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Olson Laboratories, Inc.
421 East Cerritos Avenue
Anaheim, California 92805
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-01-1957
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Protection Agency
Mobile Source Enforcement Divison
401 M Street S.W.
Washington, D.C. 20460
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
is. ABSTRACT
final' report documents the methodology and results of Phase II 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 II of the
study investigated the emission-criticality of after-market equipment not installed
or distributed by the original engine or vehicle manufacturers.
A computer model was developed to calculate and rank-order an index repre-
senting the criticality of each component type. Separate.rankings were developed
for HC, CO, NO and smoke (heavy-duty diesel engines) emissions using three indepen-
dent sets of iffput data. 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
compononto wao PGCommondod to develop or rofino data on emission increases and
symptoms of failure.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS [c! COS AT I Field/Group
13. DISTRIBUTION STATEMEN1
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Farm 2220-1 (9-73)
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