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United States Environmental Protection Agency
Office of Air and Radiation
MOTOR VEHICLE TAMPERING SURVEY - 1987
August 1988
FIELD OPERATIONS AND SUPPORT DIVISION
OFFICE OF MOBILE SOURCES
Washington, D.C.
U.S. Environmental Protection Agency
Region V, Library
230 South Dearborn Street
Chicago, Illinois 60604
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TABLE OF CONTENTS
EXECUTIVE SUMMARY 1
Introduction 1
Conclusions 3
BACKGROUND 8
SURVEY METHODS 10
Site Descriptions 13
RESULTS 19
Vehicle Tampering 19
Site and Aggregate Totals 19
Types of Tampering 21
Vehicle Characteristics and Tampering 25
Manufacturer 25
Vehicle Type 27
Vehicle Age 28
Impact of I/M and Antitampering Programs 32
Tampering Trends for Selected Sites 37
Correlation Between Tampering and Idle Emissions 41
Fuel Switching 46
Fuel Switching Indicators and Overlap 46
Fuel Switching Trends 50
Fuel Switching by Vehicle Type 54
Fuel Switching and Catalyst Tampering 54
Gasoline Lead Concentrations 58
APPENDICIES
A. Relevant Portions of Clean Air Act 59
B. Survey and Data Recording Procedures ., 60
C. Emission Cutpoints for I/M Areas 73
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LIST OF FIGURES
1. Tampering rates for selected components by program
type 5
2. (a) Overall tampering by vehicle age for vehicles
not covered by I/M and/or antitampering programs.
(b) Comparison of catalyst tampering by vehicle age
between vehicles covered and not covered by a
catalyst inspection program 7
3. Breakdown of surveyed vehicles by condition and
extent of tampering 20
4. Tampering rates by manufacturer: 1987 survey 26
5. Distribution of unleaded vehicles surveyed
among tampering, fuel switching, and idle test
categories 42
6. (a) Overlap of fuel switching indicators among
misfueled vehicles for which all three indicators
were inspected.
(b) Breakdown of misfueled vehicles in 6(a) by
prevalence of each indicator 49
7. Effectiveness of plumbtesmo test and inlet restrictor
inspection in identifying misfueled vehicles in the
1983-1987 surveys. Only includes vehicles which
have not been subject to an ATP with plumbtesmo .... 51
8. Overlap of catalyst tampering and fuel switching
among catalyst-equipped vehicles - 1987 survey 55
9. (a) Overlap of indicators used by ATPs to detect
missing/damaged catalysts. Only includes vehicles
for which all three indicators were inspected and
are not covered by an ATP with plumbtesmo testing.
(b) Breakdown of vehicles in 9(a) by prevalence
each indicator combination 57
10. Distribution of lead concentrations in leaded fuel
sampled from fuel switched vehicles. Percentages
based on all fuel switched vehicles, including
those using unleaded fuel (<0.05 gpg.) 59
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LIST OF TABLES
1. 1987 Tampering Survey Summary 22
2. Prevalence of Tampering by Component 23
3. Component-Specific Tampering Rates (percent) by
Survey Location - 1987 Survey 24
4. Tampering Percentage (and Sample Size) by Model
Year and Vehicle Age at Time of Survey 29
5. Percentage of Catalyst Removal (and Sample Size)
among Catalyst-Equipped Vehicles by Model Year
and Vehicle Age at Time of Survey 30
6. Classification of 1987 Survey Sites by Program
Status (and Model Year Coverage of Program) 35
7. Tampering and Fuel Switching Rates by Program Type:
1987 Survey 35
8. Comparison of 1987 Survey Sample to Actual
Nationwide Vehicle Fleet 36
9. Tampering Prevalence among Vehicles and Components
Covered by Antitampering Programs in ATP-only
Areas Surveyed between 1982-1987 38
10. Tampering Prevalence among Vehicles and Components
Covered by Antitampering Programs in I/M + ATP
Areas Surveyed between 1982-1987 39
11. Idle Test Failure Rates (Percent) by
Pollutant and Vehicle Condition 44
12. Mean Idle Emissions for Tampered and Okay Vehicles
Within Each Program Type 44
13. Fuel Switching Rates among Unleaded Vehicles by
Site and Indicator: 1987 Survey 52
14. Combined Tampering and Fuel Switching Rates
- 1987 Survey 53
15. Prevalence of Fuel Switching Indicators by Vehicle
Type 55
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EXECUTIVE SUMMARY
INTRODUCTION
Under the direction of the Field Operations and Support
Division (FOSD) of the Environmental Protection Agency (EPA),
contract personnel from Colorado State University (CSU)
conducted a survey of light-duty motor vehicle tampering in
15 cities between March and September, 1987. The areas surveyed
and the total number of vehicles inspected are listed below.
Miami, FL 450 Nashville, TN 505
El Paso, TX 500 Atlanta, GA 531
Houston, TX 500 Spokane, WA 382
Dallas, TX 508 Portland, OR 531
Tulsa, OK 500 Fresno, CA 500
Maryland (DC Suburbs) 450 New Orleans, LA 500
Newark, NO 431 Covington, KY 500
Charlotte, NC 600
TOTAL 7,388 vehicles
The objectives of this survey were:
1. To make local measurements of the types and extent of
tampering and fuel switching.
2. To extend and update the knowledge gained from earlier
surveys on:
a. The effect of vehicle inspection and maintenance
(I/M) programs and antitampering programs (ATPs)
on tampering and fuel switching.
b. The relationship between tampering and vehicle
idle emissions.
c. The distribution of tampering by vehicle age,
type, manufacturer, and other variables of
interest.
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To achieve these objectives, the inspection teams
visually examined emission control devices and measured the
idle hydrocarbon (HC) and carbon monoxide (CO) emissions of
each vehicle. To provide information on fuel switching, the
inspectors sampled gasoline from the tanks of vehicles (for
later laboratory lead analysis), tested for lead deposits in
tailpipes using Plumbtesmo test paper, and checked the
integrity of the fuel filler inlet restrictors. Four cate-
gories were used to summarize the condition of the inspected
vehicles:
1. Tampered - at least one control device removed or
rendered inoperative
2. Arguably Tampered - possible but not clear-cut
tampering (i.e., may have resulted from either
tampering or malmaintenance)
3. Malfunctioning
4. Okay - all control devices present and apparently
operating properly
These brief but thorough inspections were performed with the
consent of the vehicle owners in a variety of settings more
fully detailed elsewhere in this report.
The site selection in recent tampering surveys has been
based more on the need to evaluate control program effective-
ness than the desire to methodically sample the U.S. vehicle
population. Fourteen of the fifteen cities in the 1987 survey,
for example, have an inspection/ maintenance (I/M) and/or an
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antltampen'ng program (ATP), even though somewhat less than
half of the vehicles nationwide are subject to such programs.
The presence of only one non-I/M site in the 1987 survey
makes it inappropriate to use this survey as representative
of the nationwide vehicle population. Rather, the 1987 survey
sample is an appropriate tool for evaluating tampering prevalence
at any particular site, and for evaluating control program
effectiveness where "before" and "after" data exist. This
report will refrain from comparing the overall 1987 survey
results with prior surveys because of the overrepresentation
of control programs in the survey sample.
CONCLUSIONS
Tampering among vehicles not covered by I/M and/or anti-
tampering programs was 32%, compared to 20%, 18%, and 16% for
those vehicles covered by I/M-only, ATP-only, and I/M + ATP,
respectively. Such comparisons between program categories
should be made carefully, since some of the control programs
cover only newer model years of vehicles, which historically
have lower tampering rates than the older vehicles not covered
by the control programs.
Because of the large variation in program types and
coverages, the vehicles are classified based on the program
restrictions within each site. In Tulsa, for example, only
the 1979 and newer vehicles are covered by the area's anti-
tampering program; the 1975-1978 vehicles are thus classified
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as "non-I/M". The effectiveness of control programs in
deterring tampering among components and model years covered
by each specific program will be investigated later in this
report.
Fuel-Related Tampering
The prevalence of vehicles with missing or damaged
catalytic converters within each program type is depicted in
Figure 1. A vehicle can be considered to have a missing or
inoperative catalyst if the converter has been removed, the
inlet restrictor is tampered, or the plumbtesmo test is positive.
(These three criteria are used by many antitampering programs.)
A missing or damaged converter can increase HC and CO emissions
by an average of 475% and 425%, respectively. For vehicles
equipped with three-way converters, substantial increases in
NOx emissions would also be expected. In addition, converter
tampering on trucks was found to be greater than on automobiles
(6% vs. 4%).
Fuel switching, defined as the presence of any of three
2
specific indicators , was found in 14% of the unleaded vehicles
not covered by I/M and/or ATPs in the 1987 survey. Fuel
The emissions increases mentioned in this report are
from a study of three-way catalyst vehicles presented in
Anti-Tampering and Anti-Misfuel ing Programs to Reduce
in-use Emissions from Motor vehicles"!t^A-AA-l T5-83-10,
December 31,1983.
2
The three fuel switching indicators are: a tampered fuel
filler inlet restrictor, a positive Plumbtesmo tailpipe
test, or a gasoline lead concentration of more than 0.05 gram
per gal 1 on.
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Component
Catalytic Converter
Inlet Restrictor
Positive Plumbtesmo
27.
27.
17.
12%
Tampering (%)
13%
non-I/M
I/M-only
ATP-only
I/M + ATP
Figure 1. Tampering rates for selected components by
program type.
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switching among vehicles in I/M-only, ATP-only, and I/M + ATP
areas was 9%, 5%, and 5%, respectively. The pattern of overlap
among the three misfueling indicators is discussed in detail
later in this report. While the emissions impact of fuel
switching depends upon its duration and certain vehicle
characteristics, emission increases of 475% for HC and 425% for
CO can easily occur.
Catalyst Tampering and Vehicle Age
The probability that a vehicle has been tampered with
is clearly related to its age, as has been shown in previous
surveys. This is evident in Figure 2(a), which depicts
overall tampering as a function of vehicle age for those
vehicles not covered by I/M and/or antitampering programs.
Figure 2(b) compares the impact of vehicle age on catalyst
tampering among vehicles covered and not covered by converter
inspection programs. Overall, converter tampering is much
lower on vehicles covered by converter inspection programs
than on vehicles not covered by such programs (10% vs. 2%),
and the effectiveness of inspection programs is particularly
noticeable among the oldest vehicles surveyed (vehicles that
are most likely to be tampered with).
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Overall Tampering (Z)
60
3 4 5 6 7 8 9 10 11 12 13
Vehicle Age (years)
(a)
Catalyst Tampering (%)
40
Vehicles Not
Covered
Vehicles
Covered
10 -
10 11 12 13
Figure 2 (a)
2(b)
6789
Vehicle Age (years)
Cb)
Overall tampering by vehicle age for vehicles
not covered by 1/M and/or antitampering programs.
Comparison of catalyst tampering by vehicle
age between vehicles covered and not covered by a
catalyst inspection program.
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BACKGROUND
EPA estimates that motor vehicle emissions nationwide
account for 58% of the total carbon monoxide (CO), 38% of the
airborne lead, 27% of the hydrocarbons (HC), and 34% of
o
the oxides of nitrogen (NOx) emitted into the atmosphere. As
a result, a major focus of the nation's efforts to achieve
compliance with clean air standards has been the control of
emissions from mobile sources. The first pollution control
devices were installed on vehicles in 1962, and most light-
duty vehicles manufactured since 1968 have been equipped with
a variety of emission control devices to meet required
emissions standards.
The 1977 amendments to the Clean Air Act (sections
203(a)(3)(A) and (B), found in Appendix A) make it illegal for
automobile dealers, repair and service facilities, and fleet
operators to disconnect or render inoperative emission control
devices or elements of design. Regulations issued under section
211(c) of the Act (40 CFR Part 80) prohibit retailers and
wholesale purchaser-consumers from introducing or allowing the
introduction of leaded gasoline into vehicles labeled "unleaded
gasoline only". The EPA's Field Operations and Support Division
(FOSD), formerly the Mobile Source Enforcement Division (MSED),
National Air Pollutant Emission Estimates, 1940-1986,
EPA-4bU/4-8/-U24, January,
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is responsible for enforcing the tampering and misfueling
provisions of the Act.
Before 1978, the EPA had data suggesting that tampering
with emission control devices and misfueling of "unleaded only"
vehicles with leaded gasoline were occurring. Variability in
the inspection procedures, however, prevented an accurate
assessment of the nature and extent of the tampering. As a
result, the Agency began conducting nationwide tampering
surveys of light-duty motor vehicles in 1978 to determine the
rates and types of tampering and fuel switching. These
annual surveys have been conducted either by FOSD directly or
by EPA's National Enforcement Investigations Center (NEIC)
under the direction of FOSD. Consistent inspection procedures
were used throughout these surveys to permit comparisons and
identification of trends..
The uses for the tampering surveys have evolved since the
first survey was conducted in 1978. Since 1983, the tampering
survey results for some locations have been used to calculate
credits for State Implementation Plans (SIPs), the measures
taken by State and local governments to achieve ambient air
quality standards by reducing mobile source emissions. Data
from the surveys is also used in the default database for the
Agency's mobile source computer model (currently MOBILES and
being updated to MOBILE4) to estimate both the emissions
loading impact and the reductions that may be achieved by
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various control programs. Comparing survey results before
and after implementation of a control program is an excellent
method for evaluating program effectiveness. Sites for the
surveys are chosen in light of the need for data on specific
areas either currently operating or considering programs, as
well as the continuing need to monitor the types and extent
of tampering and fuel switching nationwide.
SURVEY METHODS
The 1987 tampering survey was conducted for FOSD by the
National Center for Vehicle Emissions Control and Safety at
Colorado State University (CSU). Approximately 400 to 600
vehicles were inspected in each of 15 cities between March
and September, 1987, and the entire survey includes 7,388
vehicles. The mix of vehicles inspected was assumed to be a
self-weighting sample, and no attempt was made to approximate
the national vehicle mix.
Each inspection team consisted of at least four members:
three CSU personnel, one or two EPA representatives, and fre-
quently a State or local agency representative. The CSU
personnel, assisted by the State or local person, performed
the actual inspections, while the EPA representative(s)
monitored the survey. Each vehicle inspection included the
fol1 owing:
1. Basic vehicle identification data recorded (year,
make, model) ;
2. All emission control systems checked;
3. Idle HC and CO emissions measured;
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4. Fuel sample collected from unleaded-only vehicles for
lead analysis;
5. Tailpipe tested for lead deposits using Plumbtesmo
test paper; and
6. Integrity of fuel inlet restrictor checked.
A number of changes have been incorporated into the
survey methodology in 1987. The most significant change was
the elimination of the limiter cap inspection, which has
greatly reduced the number of arguably tampered vehicles and
concurrently increased the percentage of okay vehicles.
Minor changes in the survey include the reelassification of a
removable nozzle adaptor in the inlet restrictor as "tampered".
In previous surveys this condition was coded "okay". This
particular change did not noticeably increase the inlet
restrictor tampering rate, since only 10 vehicles were affected
"Non-Stock" codes (considered properly functioning) have also
been added for the catalytic converter and inlet restrictor,
and additional classification codes were added for the EGR
control valve and sensor. The inspection and recording
procedures are detailed in Appendix B.
The survey data base has been reviewed by CSU and EPA to
ensure its accuracy, and has been offered to the major
automotive manufacturers to review the classification and
reporting of their respective vehicles.
4 (R\
PIumbtesmo^ is a registered trademark, and appears hereafter
without theฎ. It is manufactured by Machery-Nagel , Duren, W.
Germany, and marketed by Gal 1ard-Schlesinger Chemical Corp.,
Carle Place, New York.
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The tampering survey included only 1975 and newer
light-duty cars and trucks fueled with gasoline. For the
purposes of the tampering surveys, a vehicle is considered
to be "unleaded" if a dash label, tank label, or filler inlet
restrictor is observed at the time of the inspection, or if
the emission control label indicates an unleaded fuel
requirement (i.e., catalyst-equipped). A vehicle's designation
as "unleaded" or "leaded" may be changed upon subsequent
review of the data. Fuel switching rates are thus based
only on the population of unleaded vehicles surveyed.
Similarly, tampering rates for specific components are based
only on the vehicles originally equipped with the component.
The inspections were performed with the consent of the
vehicle owners at either roadside pullovers or inspection
stations. The survey was designed to minimize the refusal
rate of potential survey participants. A high refusal rate
increases the uncertainty in the data gathered, since
individuals who have tampered with or misfueled their vehicles
are less likely to allow their vehicles to be surveyed. The
overall refusal rate was very low (4%), however, and no
survey sites had a refusal rate over 10%. A brief description
of each survey site follows. Unless otherwise noted, the
survey sites within a given city were changed daily.
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SITE DESCRIPTIONS
Miami, FL - ATP-only
Dates: March 23 - 27, 1987
Vehicles Surveyed: 450
Fuel Samples: 307
Refusal Rate: 4%
The Metro-Dade Police Department provided officers to
stop potential survey participants, and the inspectors solicited
permission to conduct the inspections. Miami's inspection
program consists of a random roadside tampering check of 1%
of the vehicle fleet (1975 and newer). The tampering
inspection covers all emission control devices, and includes
a Plumbtesmo test.
El Paso, TX - I/M + ATP
Dates: April 6 - 10, 1987
Vehicles Surveyed: 500
Fuel Samples: 399
Refusal Rate: 4%
Houston, TX - ATP-only
Dates: April 13 - 17, 1987
Vehicles Surveyed: 500
Fuel Samples: 418
Refusal Rate: 4%
Dallas, TX - ATP-only
Dates: April 20 - 24, 1987
Vehicles Surveyed: 508
Fuel Samples: 399
Refusal Rate: 7%
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Roadside pullovers in El Paso, Houston, and Dallas were
conducted with the assistance of the Texas Department of
Public Safety. The decentralized antitampering program in
each city includes Plumbtesmo testing and inspection of the
catalytic converter and inlet restrictor on 1980 and newer
vehicles, and inspection of the PCV, evaporative, air pump,
and EGR systems on 1968 and later vehicles. El Paso also has
an I/M program for checking tailpipe CO emissions.
Tulsa, OK - ATP-only
Dates: April 27 - May 1, 1987
Vehicles Surveyed: 500
Fuel Samples: 427
Refusal Rate: 3%
The Tulsa survey was conducted in Tulsa (four days) and
Sepulpa. The Oklahoma Highway Patrol, Tulsa Police Department,
and Sepulpa Police Department assisted with the roadside
pullovers. Tulsa's decentralized antitampering program
includes a check of all emission control components and
Plumbtesmo testing on 1979 and newer vehicles.
Maryland (DC Suburbs) - I/M + ATP
Dates: May 11 - 15, 1987
Vehicles Surveyed: 450
Fuel Samples: 346
Refusal Rate: 1%
The Maryland survey was conducted in the Maryland suburbs
of Washington, D.C. The Maryland State Police assisted with
the roadside pullovers. Maryland's control program covers
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the last 12 model years, and consists of an annual,
centralized I/M program, and an inspection of the catalytic
converter, inlet restrictor, and air injection system upon
change of ownership.
Newark, New Jersey - I/M + ATP
Dates: May 18 - 22, 1987
Vehicles Surveyed: 431
Fuel Samples: 331
Refusal Rate: 8%
The Newark survey was conducted using roadside pullovers
in Newark, Jersey City, Secaucus, Paramus, and Ridgewood with
the help of the local law enforcement officers in these
municipalities. New Jersey's centralized I/M + ATP includes
inspection of the catalytic converter and inlet restrictor
on 1975 and newer vehicles.
Charlotte, NC - I/M + ATP
Dates: June 1-5, 1987
Vehicles Surveyed: 600
Fuel Samples: 499
Refusal Rate: 0%
Roadside pullovers were conducted with the assistance of
the Charlotte Police Department. Charlotte's I/M + ATP covers
the last twelve model years and includes inspection of the
catalytic converter, air injection system, PCV system, inlet
restrictor, and heated air intake.
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Nashville, TN - I/M-only
Dates: June 8 - 12, 1987
Vehicles Surveyed: 505
Fuel Samples: 395
Refusal Rate: 3%
The Metro Police assisted with the roadside pullovers.
Nashville's centralized I/M program covers the last twelve
model years.
Atlanta, 6A - I/M + ATP
Dates: June 15 - 19, 1987
Vehicles Surveyed: 531
Fuel Samples: 445
Refusal Rate: 9%
Roadside pullovers were conducted in Atlanta, Sandy
Springs, Smyrna, Tucker, and Lilburn with the assistance of
the Georgia State Police. The decentralized I/M + ATP in the
Atlanta area (four counties) covers the last twelve model
years and includes inspection of all emission control devices.
Spokane, VJA - I/M-only
Dates: August 13 - 17, 1987
Vehicles Surveyed: 382
Fuel Samples: 327
Refusal Rate: 3%
The Spokane survey was conducted at the city's centralized
inspection station the entire week. Spokane's I/M program
covers the last thirteen model years.
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Portland. OR - I/M + ATP
Dates: August 20 - 24, 1987
Vehicles Surveyed: 531
Fuel Samples: 453
Refusal Rate: 9%
The roadside pullovers were conducted in Portland,
Oregon City, Tualatin, Gresham, and Beaverton with the
assistance of the local law enforcement agencies. Portland's
centralized biennial I/M + ATP includes a check of all
emission control devices on 1975 and newer vehicles.
Fresno, CA - I/M + ATP
Dates: July 27 - 31, 1987
Vehicles Surveyed: 500
Fuel Samples: 442
Refusal Rate: 2%
The California Highway Patrol assisted with the roadside
pullovers. Fresno's decentralized, biennial I/M + ATP covers
the last 20 model years, and includes a check of all emission
control devices on all vehicles.
New Orleans, LA - non-I/M
Dates: August 24 - 28, 1987
Vehicles Surveyed: 500
Fuel Samples: 442
Refusal Rate: 2%
The New Orleans survey was conducted at the city's main
safety inspection facility the entire week.
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Covington, KY - ATP-only
Dates: August 31 - Sept. 4, 1987
Vehicles Surveyed: 500
Fuel Samples: 338
Refusal Rate: 3%
Roadside pullovers were conducted at five locations in
Boone, Campbell, and Kenton counties with the assistance of
the local law enforcement agencies. The decentralized ATP in
these three counties includes all emission control devices
and Plumbtesmo testing on all 1980 and newer vehicles.
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RESULTS
A. VEHICLE TAMPERING
1. Site and Aggregate Totals
The vehicles surveyed have been classified into four
categories established by previous surveys: tampered,
arguably tampered, malfunctioning, and okay. Each vehicle
was classified by the worst state of any component in the
vehicle. For example, a vehicle would be classified as
"tampered" if any one component had been tampered, even if
all other components were functioning properly. A vehicle
classified as "okay" must have all observed components
functioning properly . The criteria used for component
classification are presented in Appendix B. This overall
tampering rate is useful only as a rough indicator of the
emissions impact of a tampering problem, since the different
components making up the rate may have widely varying emissions
imp!ications.
The proportion of inspected vehicles with at least one
tampered component was 19%. One-third of the surveyed vehicles
displayed some form of malfunction, arguable tampering, or
clear tampering of emission control components. The specific
distribution of surveyed vehicles among these categories is
depicted in Figure 3.
An "okay" vehicle, however, may still be classified as
fuel switched (see section B.I., Fuel Switching Indicators
and Overlap of this report).
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The frequency distribution of tampering instances for
those vehicles classified as "tampered" is also shown in
Figure 3. Forty-one percent of the tampered vehicles had
multiple components tampered, and 14% had four or more
instances of tampering.
Table 1 summarizes the 1987 survey data by site. As
in previous surveys, the overall tampering in 1987 varies
considerably from site to site. This can be attributed
to the variety of program configurations among the cities
surveyed and to geographic differences.
Table 1 also contains the refusal rate at each survey
site. The overall refusal rate for the survey was very low
(4%), and no survey site had a refusal rate exceeding 10%.
2. Types of Tampering
The tampering rates for all emission control components
and systems surveyed in 1987 are presented in Table 2. The
component-specific tampering rates for the 1987 survey are
presented by survey site in Table 3. Only those vehicles
originally equipped with a particular component are considered
when computing the tampering rate for that component.
Table 2 shows that air pump system tampering remains the
single most tampered component (8% of equipped vehicles).
Also of interest is the slight but measurable tampering found
with the oxygen sensor and computer control system. Because
of the difficulty in inspecting the oxygen sensors (no determi-
nation could be made on nearly 200 vehicles), tampering with
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TABLE 1
1987 Tampering Survey Summary
Survey
Location
Miami, FL
El Paso, TX
Houston, TX
Dallas, TX
Tulsa, OK
Mary! and
(DC Suburbs)
Newark, NJ
Charlotte, NC
Nashville, TN
Atlanta, GA
Spokane, WA
Portland, OR
Fresno, CA
New Orleans, LA
Covington, KY
Number of
Vehicl es
450
500
500
508
500
450
431
600
505
531
382
531
500
500
500
Tampering
Rate (%)
23
26
23
19
20
12
17
15
20
15
19
8
21
23
19
Misfuel ing
Rate (%)
4
9
7
9
10
2
4
5
10
4
8
3
12
7
7
Survey
Type*
R
R
R
R
R
R
R
R
R
R
C
R
R
C
R
Refusal
Rate (%)
4
4
4
7
3
1
8
0
3
9
3
9
2
2
3
OVERALL
7,388
19
*R = roadside pullovers, C = centralized inspection stations
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TABLE 2
Prevalence of Tampering by Component
Tampering
Component/System Rate (%)
Catalytic Converter 4
Filler Neck 6
Restri ctor
Air Pump System 8
Air Pump Belt 7
Air Pump/Valve 5
Aspirator* 2
PCV System 5
Evaporative 5
Control System
EGR System 6
EGR Control Valve 5
EGR Sensor 4
Heated Air Intake 2
Oxygen Sensor 1
Computer System 1
* Vehicles with aspirated air systems are not equipped with
other listed air-injection components, nor do conventional
systems include aspirators.
------- OCR error (C:\Conversion\JobRoot\00000A3X\tiff\2000U8PH.tif): Unspecified error
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this component may be significantly different than is reported
here. As the vehicle fleet equipped with oxygen sensors and
computers ages, the tampering rates for these relatively new
devices may increase.
Table 3 shows the wide variation in tampering from site
to site for any given component. Air pump system tampering
for example, ranged from 2% in Charlotte to 18% in Miami.
This range is partly due to the effectiveness of I/M and
antitampering programs (as will be discussed later in this
report), geographic location, and socioeconomic background.
3. Vehicle Characteristics and Tampering
The next section of this report investigates the impact
on tampering of three vehicle characteristics: manufacturer,
vehicle type (car or truck), and age.
Manufacturer. Figure 4 presents the 1987 tampering
rates for each major manufacturer. The smaller foreign
manufacturers have been combined into two groups, Other
European and Other Asian. Vehicle tampering was higher among
vehicles of domestic manufacture than among those of foreign
manufacture. Overall, tampering with domestically manufac-
tured vehicles was over three times that found for the
foreign manufactured vehicles (23% vs. 7%).
A number of factors might explain the difference in
tampering prevalence among manufacturers. Differences in
design may make some vehicles more tamper-prone than others.
-------
-26-
M
\
\
1
A
t
1
rui u r -
GGHSPQ 1
25%
22%
Chrv<= 1 er/AMC 1 1
20%
Volksw
Dther EL
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a 17%
n
il ODeqn
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Ar~ ""
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Toypta 1
7%
A Mazda 1
5%
A Nissan 1
.
1
Other
5%
Asian 1
5%
A 1 ' Honda 1
I
2%
Tampering (%)
Figure 4. Tampgring by Manufacturer:
1987 Survey.
-------
-27-
Changing market share history results in different age distri-
butions for vehicles of different makes, and vehicle age is
clearly related to tampering prevalence. Tampering rates
seem to vary with geographic location and socioeconomic
background, so the owner demographics for different makes may
affect the likelihood of tampering.
Vehicle Type. The overall tampering prevalence for
light-duty trucks (LDTs) was 17%, compared to 19% for automo-
biles (LDVs). The 1987 survey is the first in which overall
tampering with cars exceeded that for trucks. While the
overall tampering rate is less meaningful than the rates for
individual components, even the component-specific truck rates
tend to converge upon the usually lower automobile rates. As
was mentioned earlier, the most critical components (e.g.,
catalytic converters) are still tampered with more frequently
on trucks.
Many factors may be contributing to the convergence in car
and truck tampering. Since most of 'the vehicles surveyed in
1987 were subject to control programs, the relative car and
truck tampering rates may reflect increased emphasis on truck
tampering detection by the inspection programs. Also, the
proportion of imported trucks within the total truck population
surveyed has increased from 15% to 23% between 1982 and 1987,
with many of the smaller trucks being utilized as cars.
-------
-28-
Since imported vehicles are tampered with much less frequently
than domestic vehicles, the increase in imported trucks within
the truck population surveyed may be contributing to the lower
truck tampering prevalence. Another contributing factor may
be the delayed impact of closed loop technology on truck
tampering relative to car tampering. Closed loop technology
first became widespread on trucks in 1983, while it has been
widely used on cars since 1981. Any tampering deterrence^
from closed loop technology should thus be evident on cars
first and then later on trucks.
Vehicle Age. Table 4 relates vehicle age and model year
with tampering prevalence for the 1978-1987 surveys. Catalytic
converter removal rates are similarly related to vehicle age
and model year in Table 5. The results from any given survey
are entered diagonally in each table.
The results in Tables 4 and 5 indicate that vehicle
tampering increases directly with vehicle age. Examining
Table 4 diagonally (by survey) shows that tampering increases
consistently with vehicle age in each survey conducted. In
the 1987 survey, for example, the tampering rate increases
from 1% for first year (1987) vehicles to 65% among the 1975
model year vehicles surveyed.
Table 5 shows a similar, though less pronounced, increase
in catalyst removal. The catalyst tampering rate remains
negligible tor the first five years of a vehicle's life, and
then increases thereafter. This delay in catalyst tampering
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-31-
is understandable, since the emission control components on
all new vehicles are warranted for 5 years/50,000 miles by
the manufacturer, providing an incentive to maintain the
catalysts on vehicles still under warranty. A similar delay
in overall tampering is not readily apparent in Table 4, but
becomes evident when only non-I/M vehicles are examined
(Figure 2(a)). Examining these tables in this manner has the
advantage of comparing data collected during one survey in
one set of locationss but ignores the possible effects of
model year differences (i.e., technology), geography, or
program coverage on tampering.
Two additional ways of analyzing Tables 4 and 5 address
the impact of model year on tampering rates. Analyzing the
tables horizontally (holding the model year constant) provides
a look at the tampering rates over time for the vehicles of
a particular model year. This approach shows the same distinct
increase in tampering with vehicle age for all model years
since 1975. (The 1974 and 1973 data sets are too small to
permit any conclusions.) The increase in tampering, however,
is less pronounced for newer model year vehicles. For
example, the tampering incidence for 1982 model year vehicles
increases from 1% in their first year to 19% by their sixth
year of use. In contrast, the tampering incidence for 1978
model year vehicles increased from 7% to 39% over the first
six years of their use. A similar examination of Table 5
reveals that converter tampering also remains lower for newer
model year vehicles.
-------
-32-
Tables 4 and 5 can also be examined vertically (holding
vehicle age constant), which provides a look at the tampering
rates for different model year vehicles of the same age.
This approach permits a crude examination of trends in tamper-
ing adjusted for vehicle age. Examining Table 4 vertically,
for example, shows a decrease in overall tampering from the
1978 survey to the 1987 survey for vehicles in their third
year of use. A similar vertical analysis of Table 5 does not
show any clear pattern or trend in age-specific catalyst
tampering.
The comparisons made in the two preceding paragraphs
involve observations made in different survey locations during
different years, and are affected by the site selection in
each survey. An increasing percentage of the 1981 and newer
vehicles in recent surveys have been covered by antitampering
programs, which could contribute to the lower tampering found
among newer vehicles. The impact of improved technology on
tampering could be more accurately assessed by examining only
vehicles from non-I/M areas, but only one non-I/M area was
surveyed in 1987. The representativeness of the 1987 survey
sample will be discussed later in this report.
4. Impact of I/M and Antitampering Programs
Inspection and maintenance (I/M) programs require vehicles
to meet specific idle emission standards. Vehicles registered
in areas with these programs are required to be periodically
-------
-33-
tested to assure that they comply with the specific idle
emission cutpoints established by these jurisdictions. In
addition to reducing emission levels by stimulating better
owner maintenance, I/M programs may deter some tampering with
emission control components. Data from previous surveys has
tended to support this proposition, since tampering in I/M
areas has historically been lower than in non-I/M areas.
Some local areas have also instituted antitampering
programs (ATPs), which involve periodic vehicle inspections
to check the integrity of specific emission control components.
Antitampering programs vary greatly in the components inspected
and the vehicle model years covered, so that a vehicle or
component which would be inspected in one program area might
not be inspected in a different program area. Successful
antitampering programs should reduce existing tampering and
deter future tampering with the components and model years
covered by the program.
Classifying the survey areas into program types is made
difficult by the considerable variation in control programs.
Miami's antitampering program, for example, is a random
roadside inspection of 1% of the vehicle fleet (1975 and
newer) for all emission control devices. Tulsa also has an
antitampering program, but inspects all 1979 and newer vehicles
for all emission control devices. The antitampering program
in Houston includes inspection of all emission control devices
on 1980 and newer vehicles, but only the PCV, evaporative,
air pump, and EGR systems on 1968-1979 vehicles.
-------
-34-
In order to minimize these variations in program types
and model year coverages, the vehicles in the 1987 survey can
be classified by the model year restrictions applicable in the
program areas surveyed. These classifications are shown in
Table 6, and the tampering and fuel switching rates by program
type are listed in Table 7. Since Tulsa's program only covers
1979 and newer vehicles, for example, only those model year
vehicles are classified as "ATP-only"; the 1975-1978 vehicles
surveyed in Tulsa are classified as "non-I/M". This method
of classification does not take into consideration the compo-
nents inspected by each program, a program's effectiveness,
or the frequency of inspection. Any comparisons between
program types (i.e., I/M-only vs. non-I/M) should thus be
made carefully.
Another factor hindering comparisons in Table 7 is the
overrepresentation in the survey sample of areas with some
kind of control program. This is a deliberate feature of the
survey's design, as was discussed earlier, and focuses
attention on evaluating the effectiveness of specific indivi-
dual programs. Table 8 compares the proportion of the 1987
survey sample and the national vehicle fleet under control
programs. Because of the need to evaluate control program
effectiveness, the survey greatly overrepresents the portion
of the national vehicle fleet under control programs. Vehicles
covered by a control program comprised Bl% of the survey
sample, while only approximately 38% of the national vehicle
-------
-35-
Table 6
Classification of 1987 Survey Sites by Program Status
(and Model Year Coverage of Program)
T/M T/Mnn1i<
non-I/M
New Orleans, LA (all years)
Tulsa, OK (1975-1978)
Covington, KY (1975-1979)
ATP-only
Miami , FL (all years)
Houston, TX (all years)
Dallas, TX (all years)
Tulsa, OK (1979-1987)
Covington, KY (1980-1987)
I/M-only
Nashville, TN (all years)
Spokane, WA (all years)
I/M + ATP
El Paso, TX (all years)
Newark, NJ (all years)
Charlotte, NC (all years)
Atlanta, GA (all years)
Portland, OR (all years)
Fresno, CA (all years)
M a ry 1 a n d
(DC Suburbs) (all years)
Table 7
Tampering and Fuel Switching Rates by Program Type:
1987 Survey
Program
Type
non- I/M*
I/M-only
ATP-only
I/M + ATP
Tampering
Rate (%)
32
20
18
16
Fuel Switching
Rate (%)
14
9
5
5
*the non-I/M rates are included for the sake of completeness,
and should not be considered representative of non-I/M areas
nationwide.
-------
-36-
TABLE 8
Comparison of 1987 Survey Sample to Actual Nationwide
Vehicle Fleet
Program . Percentage within Approx. Percentage of
Type Survey Sample (%) Nationwide Fleet (%)*
non-I/M 9 62
I/M-only 12 11
I/M + ATP 48 18
ATP-only 31 9
* From Provisional Estimates of the Population of Counties:
July 1, 1986, U.S. Department ot Commerce - Bureau or the
Census, August, 1987.
-------
-37-
fleet were under such programs. The surveyed vehicles not
covered by a control program consist of all the vehicles in
New Orleans and the older vehicles in Covington and Tulsa,
and should not be considered representative of non-I/M areas
nationwi de.
5. Tampering Trends for Selected Sites
The impact of I/M and antitampering programs in specific
locations can be examined by comparing the 1987 survey data
with that from earlier surveys. Comparisons made between
surveys widely spaced in time, however, must take into con-
sideration the differences in average vehicle age in each
survey. The average miles traveled per vehicle surveyed in
1987, for example, is one-third greater than it was in 1982.
Since vehicle mileage correlates with vehicle age, which is
directly related to tampering prevalence, a significant
increase in tampering might be expected to have occurred
between 1982 and 1987, if all other factors remained constant
(car/truck distribution, owner demographics, etc.). Inferences
regarding program effects should thus be made with this in
mind.
Tables 9 and 10 present tampering data for the five
ATP-only and seven I/M + ATP sites surveyed, respectively.
Because of the large number of programs represented in Tables
9 and 10, only a few representative comparisons will be dis-
cussed in this report. Detailed analysis of each program's
-------
-38-
TABLE 9
Tampering Prevalence among Vehicles and Components Covered
by Antitampering Programs in ATP-only Areas Surveyed
between 1982-1987
Survey Location
(Program Start Date)
Miami, FL
(1/86)
Houston, TX
(7/84)
Dallas, TX
(1/86)
Tulsa, OK
(1/86)
Covington, KY
(9/86)
Component and
Model Years Covered
1982
Catalyst
Inlet Restrictor
Air Pump System
Pos. Plumbtesmo
Evap. System
PCV System
EGR System
Catalyst
Inlet Restrictor
Pos. Plumbtesmo
PCV System
Evap. System
Air Pump System
EGR System
Catalyst
Inlet Restrictor
Pos. Plumbtesmo
PCV System
Evap. System
Air Pump System
EGR System
Catalyst
Inlet Restrictor
Pos. Plumbtesmo
PCV System
Evap. System
Air Pump System
EGR System
Catalyst
Inlet Restrictor
Pos. Plumbtesmo
PCV System
Evap. System
Air Pump System
EGR System
75+
75+
75+
75+
75+
75+
75+
80+
80+
80+
75+
75+
75+
75+
80+
80+
80+
75+
75+
75+
75+
79+
79+
79+
79+
79+
79+
79+
80+
80+
80+
80+
80+
80+
80+
2
9
7
15
3
5
11
1
4
6
3
1
9
6
_
-
_
-
-
-
-
10
13
13
1
3
5
6
H
-
-
-
-
-
-
Tampering Prevalence (%)
by Survey Year
1983 1984 1985 1986 1987
6
1
8
9
8
9
19
7
5
8
5
5
8
9
_
_
_
_
_
_
-
1
0
2
4
4
6
9
am
_
_
_
_
_
-
_
_
_
_
_
-
_
_
_
_
_
_
_
-
-
-
-
-
-
3
2
2
7
7
8
9
^
_
-
_
_
-
-
mm
_
_
_
-
-
-
3
2
1
0
1
3
2
6
4
18
1
9
7
9
1
1
1
7
8
6
8
2
2
2
6
7
6
4
2
3
1
3
3
5
6
1
1
1
1
2
5
2
-------
-39-
TABLE 10
Tampering Prevalence among Vehicles and Components Covered
by Antitampering Programs in I/M + ATP Areas Surveyed
between 1982-1987
Survey Location
(Program Start Date)
El Paso, TX
(1/86)
New Jersey -
Varied Locations
(I/M - 2/74,
ATP - 12/85)
Charlotte, NC
(12/82)
Portland, OR
(7/75)
Fresno, CA
(10/84)
Maryland -
DC Suburbs
(2/84)
Atlanta, GA
(I/M - 4/82,
ATP - 12/86)
Component and
Model Years Covered
Catalyst
Inlet Restrictor
Pos. Plumbtesmo
PCV System
Evap. System
Air Pump System
EGR System
Catalyst -
Inlet Restrictor
Catalyst
Inlet Restrictor
PCV System
Air Pump System
EGR System
Catalyst
Inlet Restrictor
PCV System
Evap. System
Air Pump System
EGR System
Catalyst
Inlet Restrictor
PCV System
Evap. System
Air Pump System
EGR System
Catalyst
Inlet Restrictor
Air Pump System
Catalyst
Inlet Restrictor
Air Pump System
80+
80+
80+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
75+
_
-
_
-
-
-
-
_
-
-
-
-
0
0
1
1
1
10
_
-
-
-
-
-
H
-
-
_
-
-
Tampering Prevalence (%)
by Survey Year
1982 1983 1984 1985 1986
3
3
6
7
5
17
11
5
5
5
6
2
5
8
2
8
1
3
1
1
1
3
2
9
7
4
3
7
198J
2
1
1
8
7
9
9
4
4
2
5
4
3
6
2
1
2
1
4
2
1
11
4
3
8
4
1
1
6
1
3
6
-------
-40-
1s beyond the scope of this report. The comparisons made in
these Tables have been limited to the specific components and
vehicle model years covered by each antitampering program
actually in operation during the 1987 survey. The tampering
data listed in Tables 9 and 10 were compiled only for surveyed
vehicles included within the local program jurisdiction. The
Houston tampering rates listed, for example, are for Harris
County vehicles only. Any non-Harris County vehicles surveyed
were excluded from this analysis.
The data in Table 9 suggests that Miami's random 1%
roadside check does not deter tampering as effectively as
ATPs which inspect all vehicles. The data from the other
four program areas in Table 9 shows that catalyst and inlet
tampering have declined after the ATP was implemented, but
tampering with underhood components has not declined appreciably.
This weakness in inspecting underhood components may be partly
because all of the ATP-only programs surveyed are decentralized
programs, which have historically been less effective than
centralized programs in reducing tampering. Detecting under-
hood tampering is more complex and requires more training
than converter and inlet restrictor inspection. The level of
inspector training needed to implement an effective antitamper-
ing program is more easily attained when vehicle inspections
are conducted at a few centralized stations than at many
decentralized locations.
-------
-41-
Three of the I/M + ATP areas listed in Table 10 are
centralized programs (Maryland, New Jersey, and Portland),
but only in Portland had all of the covered vehicles been
exposed to the program. (Maryland's ATP applies only to
vehicles upon change of ownership, and New Jersey's ATP was
not entirely phased in until May, 1987.) Portland's long-
established program has kept tampering with covered
components, except .for air pump systems, to a minimum. The
prevalence of positive Plumbtesmo results for the areas
listed in both Tables 9 and 10 has declined dramatically
from earlier surveys.
6. Correlation between Tampering and Idle Emissions
As was mentioned previously, vehicles which are subject
to an I/M program must meet specific idle emissions cutpoints
To assess the relationship between tampering and fuel switch-
ing and idle failure rates, the idle emissions from unleaded
vehicles have been tested against the cutpoints established
by the I/M program where they were sampled. Vehicles in non-
I/M and ATP-only areas were tested against the cutpoints
specified by the New Jersey I/M program. The cutpoints for
each I/M area are listed in Appendix C.
The results of the idle tests are presented in Figure 5
for vehicles in the various tampering and fuel switching
categories. Only 10% of the unlea-ded vehicles surveyed that
were free of tampering and fuel switching failed an idle
-------
-42-
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-43-
test, while 67% of the tampered and fuel switched vehicles
failed that test. These results indicate that a substantially
larger proportion of tampered and fuel switched vehicles than
of okay vehicles fail an idle test at typical I/M cutpoints.
It should be noted from Figure 5, however, that 33% of the
tampered-and fuel switched vehicles were still able to pass
an idle test.
Tffble 11 shows the percentage of vehicles that failed
the idle emissions test for each vehicle condition. The
failure rates are listed for the entire survey, as well as
in two model year groupings representing "old" technology
(1975-1980) and "new" technology (1981+) vehicles. "New"
technology includes closed loop emissions control, which
came into widespread usage in 1981 model year vehicles.
The overall percentage of tampered vehicles exceeding
I/M cutpoints for HC emissions was over six times greater
than for okay vehicles (32% vs. 5%). Over five times as
many tampered vehicles exceeded CO cutpoints as did okay
vehicles (44% vs. 8%). The majority (64%) of the vehicles
that either had been fuel switched or had their catalysts
removed also exceeded HC or CO limits. Conversely, 36% of
the vehicles with missing catalysts or classified as fuel
switched were still able to pass an idle emissions test.
A significant number of arguably tampered vehicles also
produced excess idle emissions.
-------
-44-
TABLE 11
Idle Test Failure Rates (Percent) by Pollutant
and Vehicle Condition
Failure Rate (%) by Pollutant for
the Model Years listed
Vehicl
Condi ti
Okay
Arguabl
Tampere
Tampere
e
on
y
d
d
1975-80
HC
20
22
39
CO
35
39
54
1981 +
HC
3
9
19
CO
5
11
24
Entire Survey ( 1975+)
HC
5
15
32
CO
8
24
44
HC or
10
29
54
CO
Cat. Removed
or Misfueled
41 57
27 30
39 51
64
TABLE 12
Mean Idle Emissions for Tampered and Okay Vehicles
Within Each Program Type
Program
Type
non-I/M
I/M*
I/M (CO-only)**
ATP-only
HC emissions(ppm)
Tampered Okay
CO emissions(%)
Tampered Okay
508.2
321.1
486.3
420.3
102.6
82.7
99.6
81.9
3.2
2.1
2.9
2.8
0.7
0.4
0.6
0.5
OVERALL
406.1
86.2
2.6
0.5
* includes any program where idle emissions are checked,
including I/M + ATP areas.
** consists of Charlotte and El Paso vehicles, where only
CO emissions are checked.
-------
-45-
The effectiveness of idle emissions testing on "new"
technology vehicles can also be seen in Table 11. The data in
Table 11 actually underestimates the impact of "new" technology
because "old" technology trucks manufactured after 1980 have
been included in the "new" technology category due to the
model year split. As was found in the 1986 survey, idle
emissions testing is more effective in identifying tampering
on 1980 and older vehicles than on 1981 and newer vehicles.
For example, 54% of the tampered "old" technology vehicles
exceeded CO cutpoints compared to 24% of the tampered "new"
technology vehicles. This suggests that idle emissions testing
may not be an effective strategy for identifying tampering
and fuel switching among "new" technology vehicles, since
many vehicles with closed loop systems are able to produce
low idle emissions even with tampered emission control devices.
The mean idle emissions for tampered and okay vehicles are
presented in Table 12 by program type. The classification of
survey sites is the same as was depicted in Table 6, with two
alterations. The data from Charlotte and El Paso are listed
in a separate category (I/M-CO only) because both programs
have no HC cutpoints. The remaining I/M and I/M + ATP sites
have been combined into the "I/M" category.
The mean idle emissions from tampered vehicles were
considerably greater than from untampered vehicles (Table 12).
Overall, HC and CO emissions from tampered vehicles were
-------
-46-
approximately four times greater on average than from okay
vehicles. - Untampered vehicles from areas with I/M and ATP-
only programs had the lowest average HC and CO emissions,
respectively. Untampered vehicles in the I/M areas that
don't have HC cutpoints had average HC emissions nearly as
high as vehicles in the non-I/M areas surveyed, suggesting
that CO-only cutpoints have little impact on reducing HC
emissions in the areas surveyed.
B. FUEL SWITCHING
1. Fuel Switching Indicators and Overlap
Fuel switching is more easily defined than measured,
since no single indicator can completely characterize its
prevalence. Since 1981 the surveys have used a combination
of three indicators to measure fuel switching more accurately:
a tampered fuel filler inlet restrictor, a positive Plumbtesmo
test for lead deposits in the tailpipe, and a gasoline lead
concentration of more than 0.05 gram per gallon (gpg). Of
these three indicators, only a tampered inlet restrictor is
also considered tampering, and as such is used to calculate
both tampering and fuel switching rates. Since false positive
indications should be extremely rare for these measures, the
percentage of vehicles with at least one positive indicator
is a reasonable minimum estimate of fuel switching.
-------
-47-
Measuring fuel switching is somewhat unusual because two
of the three indicators (positive plumbtesmo and leaded fuel
in the tank) disappear with subsequent proper fueling. A
vehicle which has one or both of these transient indicators,
however, has recently used or is currently using leaded
gasoline. The presence of a tampered inlet restrictor provides
no information about the immediacy of the fuel switching. A
fuel switching rate derived from the two transient indicators
would thus measure how many vehicles have recently used leaded
gasoline, while all three indicators together provide a more
accurate indication of long-term fuel switching behavior.
The presence of any of these three indicators suggests
that a given vehicle has been misfueled; their absence, how-
ever, does not rule it out. For example, fuel samples could
only be obtained from 82% of the unleaded vehicles surveyed,
limiting the scope of this variable. A vehicle with an
untampered fuel filler inlet restrictor may also have been
fueled at a leaded pump equipped with a smaller nozzle, or by
using a funnel or similar device. The tailpipe lead test may
also fail to identify misfueling, particularly if older
vehicles have had their tailpipes replaced since last operated
on leaded fuel. As the lead phasedown program is lowering
lead levels in leaded gasoline, the incidence of false nega-
tive Plumbtesmo results may be increasing. The uncertainty
in these measures, then, is always toward underestimating the
number of vehicles misfueled.
-------
-48-
The limitations of the fuel switching indicators can be
seen in their incomplete overlap. The Venn diagram (Figure
6(a)) illustrates the degree of overlap in the misfueling
indicators for all unleaded vehicles surveyed in 1987 where
data for all three indicators were recorded. Figure 6(b)
shows the percentage of the misfueled vehicles with each
combination of the three misfueling indicators. For example,
only 19% of the misfueled vehicles exhibited all three
indicators. Only 52% of the vehicles having leaded fuel in
their tank also registered a positive Plumbtesmo test, and
only 33% of the vehicles with tampered inlet restrictors
actually had leaded gasoline in their tanks at the time of
the survey. The incomplete overlap reflects the limitations
of each indicator as well as the different aspects of fuel
switching each indicator identifies.
Figure 6(b) also shows that 87% of the fuel switched
vehicles had a tampered inlet restrictor, making it by far
the most frequently observed indicator of fuel switching.
A positive Plumbtesmo result was observed on 26% of the fuel
switched vehicles, while leaded fuel was found in the tanks
of 38% of the fuel switched vehicles sampled. An antitampering
program consisting of an inlet restrictor inspection and a
Plumbtesmo test would have detected fuel switching in 91% of
the fuel switched vehicles surveyed in 1987.
-------
-49-
Positive Plumbtosmo
(109 Total)
Loaded Fuel in Tank
(157 Total)
Tampered Inlet
Restrictor
(365 Total)
(a)
Tampered Inlet Only
(55%)
Plumbtesmo
(0%)
Leaded Gas Only
(3%)
Plumbtesmo Only
(3Z)
f Gas
All Three Indicators
(19%)
Plumbtesmo + Inlet
(4X)
Gas f Inlet (9%)
(b)
Figure 6 (a)
6(b)
Overlap of fuel switching indicators among
misfueled vehicles for which all three
indicators were inspected.
Breakdown of misfueled vehicles in 6 (a) by
prevalence of each indicator.
-------
-50-
Figure 7 depicts how the relative prevalence of the fuel
switching indicators has changed since 1983. Only vehicles
that have not been subject to an ATP with Plumbtesmo are
included in Figure 7. In each of the past five surveys,
approximately 90% of the misfueled vehicles could be detected
on the basis of a tampered inlet restrictor and/or positive
Plumbtesmo test. During that time, however, the percentage
of misfueled vehicles with tampered inlet restrictors has
increased from 56% to 90%, while the percentage with a positive
Plumbtesmo test and an intact inlet restrictor fell from 33%
to 27o. The decrease in Plumbtesmo's apparent effectiveness
as a fuel switching indicator may be linked to the lower lead
content of leaded gasoline, which may give a more transient
positive Plumbtesmo result (more false negative responses).
Such an analysis does not take into consideration any deterrent
effect Plumbtesmo testing may have on fuel switching in program
areas utilizing it.
2. Fuel Switching Trends
Of the vehicles requiring unleaded fuel, 7% were identi-
fied as misfueled by at least one of the indicators discussed
above. The fuel switching incidence by survey site is listed
in Table 13. The data in Table 13 again show that inlet
restrictor tampering is easily the most prevalent indicator
of mi sfueling.
Table 14 presents the combined tampering and fuel switching
rates for the 1987 survey. The percentage of unleaded vehicles-
that were tampered or fuel switched was 19%, and the percentage
-------
-51-
Percent of Misfueled Vehicles
100
90
80
70
60
50
40
30
20
10
0
1983 1984 1985 1986
Survey Year
1987
vehicles with pos.
plumbtesmo 8, intact
inlet restrictor
vehicles with pos.
plumbtesmo & tam-
pered restrictor
vehicles with tam-
pered restrictor &
neg. plumbtesmo
Figure 7.
Effectiveness of plumbtesmo test and inlet
restrictor inspection in identifying misfueled
vehicles in the 1983 - 1987 surveys. Only
includes vehicles which have not been subject
to an ATP with plumbtesmo.
-------
-52-
TABLE 13
Fuel Switching Rates among Unleaded Vehicles by Site and Indicator:
1987 Survey
Leaded
Survey Fuel in
Location Tank(%)
Miami , FL
El Paso, TX
Houston, TX
Dallas, TX
Tulsa, OK
Maryland (DC Suburbs)
Newark, NJ
Charlotte, NC
Nashville, TN
Atlanta, GA
Spokane, WA
Portland, OR
Fresno, CA
New Orleans, LA
Covington, KY
1
3
3
4
6
1
0
2
6
1
4
2
2
2
6
Tampered
Inlet
Restrictor(%)
4
8
6
9
8
1
4
5
8
3
7
2
11
7
6
Posi ti ve
PI umbtesmo
m
1
2
2
4
4
0
0
1
3
1
2
2
1
1
3
Overall Fuel
Swi ten ing
m
4
9
7
9
10
2
4
5
10
4
8
3
12
7
7
ALL SITES
-------
-53-
TABLE 14
Combined Tampering and Fuel Switching - 1987 Survey
Catalyst-equipped vehicles
Unleaded Vehicles
Survey
Location
Miami , FL
El Paso, TX
Houston, TX
Dallas, TX
Tulsa, OK
Mary! and
(DC Suburbs)
Newark, NJ
Charlotte, NC
Nashville, TN
Atlanta, GA
Spokane, WA
Portland, OR
Fresno, CA
New Orleans, LA
Covington, KY
with catalysts removed or
that were fuel switched (%)
7
12
9
11
11
2
6
6
12
4
9
4
12
10
8
either tampered or
fuel switched (%)
23
26
23
19
20
12
17
15
21
15
20
9
21
23
19
TOTAL
19
-------
-54-
of unleaded vehicles with missing or damaged converters was 8%.
Table 14 thus suggests that over 40% of all tampering and fuel
switching is composed of vehicles in the catalyst removed or
fuel switched category. Since these conditions have the larg-
est emissions impact, this indicates the very serious nature
of much tampering.
3. Fuel Switching by Vehicle Type
The prevalence of each fuel switching indicator by vehicle
type is presented in Table 15. Overall fuel switching among
trucks was only slightly higher than for passenger cars (7%
vs. 6%) and the prevalence of each indicator was essentially
the same for cars and trucks.
4. Fuel Switching and Catalyst Tampering
Consumers and mechanics remove catalytic converters for
a number of reasons, but some of their motivation may be
related to fuel switching. The vehicle owner may remove the
catalytic converter either prior to misfueling, or after some
misfueling if the vehicle's driveability has been adversely
affected by a catalyst damaged from the repeated misfueling.
The data from this survey cannot be used to distinguish between
these two situations, but can be used to examine the extent
to which these types of abuse occur in conjunction.
Figure 8 depicts the degree of overlap between catalyst
removal and fuel switching. Vehicles with catalyst tampering
exclusive of fuel switching were relatively uncommon -- only
41% of the catalyst tampered vehicles were not fuel switched.
-------
-55-
Table 15
Prevalence of Fuel Switching Indicators by Vehicle Type
Fuel Switching Indicator
Tampered Inlet Restrictor
Positive Plumbtesmo
Leaded Fuel in Tank
Overall Fuel Switching
Percent Fuel Switching
by Vehicle Type
LDV LOT
6
2
3
6
7
2
3
7
Catalyst Tampering
(317 Total)
Fuel Switching
(469 Total)
Figure 8. Overlap of catalyst tampering and fuel switching
among catalyst-equipped vehicles - 1987 survey.
-------
-56- .
Fuel switching, however, is not always accompanied by catalyst
removal, since 60% of the fuel switched vehicles still had
their catalysts.
Figures 9(a) and (b) examine the relationship between
converter tampering and two of the three misfueling indicators
(positive Plumbtesmo and tampered inlet restrictor). Only
vehicles that have not been subject to an ATP with Plumbtesmo
testing and in which all three of these parameters were inspected
are included in these figures. These three parameters have
been incorporated into a number of antitampering programs to
determine if a converter is missing or damaged. A vehicle
failing the Plumbtesmo test or inlet restrictor inspection in
some of these programs (e.g., Texas) is required to have its
converter replaced.
Figure 9(a) shows the value of these programmatic criteria
in detecting missing or lead-poisoned converters. A simple
inspection of the converter, tor example, would only catch 53%
of the vehicles with missing or lead-poisoned converters.
Inspecting both the converter and inlet restrictor, nowever,
would detect 98% of these vehicles. The usefulness of Plumb-
tesmo in detecting damaged converters appears to be very
limited, since only 2% of the vehicles in ngure 9(b) tailed
for Plumbtesmo only, in 1984, prior to lead phasedown, 17%
of the vehicles failing one of these programmatic criteria
failed for Plumbtesmo only.
-------
-57-
Positive Plumbtesmo
(95 Total)
Missing Catalytic
Converter
(233 Total)
Tampered Inlet
Rastrictor
(341 Total)
(a)
Tampered Inlet Only
(39%)
Plumbtesmo + Cat.
(OZ)
Converter Only (21%)
Plumbtesmo Only (2%)
All Three Indicators
(13%)
Inlet + Plumbtesmo (7%)
Cat. f Inlet (18%)
(b)
Figure 9 (a)
9(b)
Overlap of indicators used by ATPs to detect missing/
damaged catalysts. Only includes vehicles for which
all three indicators were inspected and are not
covered by an ATP with plumbtesmo testing.
Breakdown of vehicles in 9(a) by prevalence of each
indicator combination.
-------
-58-
5. Gasoline Lead Concentrations
Of the vehicles identified as misfueled by any of the
three misfueling indicators, 61% had only trace amounts of lead
(less than 0.05 gpg) in their gasoline when inspected. These
vehicles, then, were identified as fuel switched by a tampered
inlet restrictor and/or a positive Plumbtesmo test. Figure 10
presents the distribution of lead concentrations of 0.05 gpg
or more in misfueled vehicles. The impact of lead phasedown
can be dramatically seen when Figure 10 is compared to similar
data from the earlier surveys. In the 1987 survey none of the
misfueled vehicles had a gasoline lead concentration in excess
of 0.8 gpg, compared to 44% in 1984. Most of the misfueled
vehicles with leaded gas in the 1987 survey had gasoline lead
concentrations of 0.20 gpg or less.
Percentage of Misfueled Vehicles
15
10
13%
2 vx
DZ
Figure 10.
"300"
Gasoline Lead Concentration (grams/gallon)
Distribution of lead concentrations in leaded
fuel sampled from fuel switched vehicles.
Percentages based on all fuel switched vehicles,
including those using unleaded fuel (<0. 05 gpg-)
-------
-59-
APPENDIX A
RELEVANT PORTIONS OF THE CLEAN AIR ACT
Section 203(a)(3): The following acts and the causing thereof
are prohibited --
(A) for any person to remove or render inoperative any device
or element of design installed on or in a motor vehicle or
motor vehicle engine in compliance with regulations under this
title prior to its sale and delivery to the ultimate purchaser,
or for any manufacturer or dealer knowingly to remove or
render inoperative any such device or element of design after
such sale and delivery to the ultimate purchaser; or
(B) for any person engaged in the business of repairing,
servicing, selling, leasing, or trading motor vehicles or
motor vehicle engines, or who operates a fleet of motor
vehicles, knowingly to remove or render inoperative any
device or element of design installed on or in a motor
vehicle or motor vehicle engine in compliance with regulations
under this title following its sale and delivery to the
ultimate purchaser.
-------
-60-
APPENDIX B
SURVEY AND DATA RECORDING PROCEDURES
1. Explanation of Survey Forms
The forms on the following pages were used for recording
the survey data in the field. The forms were forced choice to
ensure coding consistency, and were designed to facilitate
direct data entry. The following codes were used to record
data for the major system components on the data sheets:
0 - Not originally equipped 8 - Misadjusted item
1 - Functioning properly 9 - Malfunctioning
2 - Electrical disconnect A - Stock equipment
3 - Vacuum disconnect B - Non-stock
4 - Mechanical disconnect D - Add on equipment
5 - Incorrectly routed hose Y - Yes
6 - Disconnect/Modification Z - No
7 - Missing item
Additional codes were used for those components which
could not be classified into the above categories. If a
determination could not be made about a given component's
condition, the variable was left blank. A brief description
of each data entry follows.
-------
-61-
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Form A - Underhood
1-4 ID Number - Vehicles are numbered sequentially as
they are inspected. This number is preceded by a
site identifying letter.
5-8 Month and year of last I/M inspection (left blank
if vehicle is licensed in non-I/M area).
9-12 Displacement - as recorded on the underhood emission
label.
13-14 Vehicle Model year
15-25 Engine Family - as recorded on the underhood emission
label .
26-36 Non-serial number portion of VIN - as recorded on the
driver's side of the dash under the windshield or the
driver's door post. The VIN is recorded only if the
engine family can not be determined.
37 Originally Catalyst Equipped - as recorded on the
underhood emission label or the driver's door post.
38 Engine Change - is coded 'Y' if the vehicle: has a
different gasoline engine than was originally equipped;
was originally equipped with a diesel engine and
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-64-
currently has a gasoline engine; was converted to
operate on a fuel other than gasoline or diesel fuel
(i.e., propane); or is a "gray market" imported vehicle
39 Air Cleaner - is coded 'A1, 'B1, or '7'.
40 Heated Air Intake - provides warm air to the carburetor
during cold engine operation. The heated air intake
is coded '0', 'I1, '3', '4', '7' (stovepipe hose),
'9' (vacuum override), or 'B1 (custom air cleaner),
41 Positive Crankcase Ventilation (PCV) system - prevents
crankcase emissions by purging the crankcase of blow-
by gases which leak between the piston rings and the
cylinder wall in the combustion chamber under high
pressures. The PCV system is coded 'I1, '3', '4'
(fresh air hose), '7', '9', or 'B1 (includes fuel
economy devices).
42 Turbocharger - coded '0', 'A1, 'B', or 'D'.
43 Evaporative Control System (ECS) - controls vapors
from the ruel tank and carburetor. Some systems have
two lines: from the fuel tank to the canister, and
from the canister to the carburetor or air cleaner
{for purging the canister). Other systems have a
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-65-
third line connected to the carburetor. The ECS is
coded '!', '3' (carburetor line), '4' (tank line),
'5', '6' (air cleaner unsealed), '?', or '9' (cracked
hose or cam' ster).
Air Injection System - extends the combustion process
into the engine's exhaust system by injecting fresh
air into the exhaust ports, lowering exhaust emissions
while still maintaining proper vehicle performance.
Two types of air injection systems are currently used.
One type uses a belt-driven air pump to direct air
through a control valve and into the exhaust manifold.
The other type is a Pulse Air Injection Reaction
(PAIR) system, which uses an aspirator commonly
located in the air cleaner to supply air to the exhaust
manifold.
44 PAIR - coded '0' (if air pump system or none), '!',
'4' , '7', or '9'.
45 Air Pump Belt - is coded '0' (if PAIR or none), '!',
'7' , or '8' (loose belt).
46 Air Pump System - for the purposes of this variable,
consists of the air pump and control valve and is
coded '0' (if a PAIR or none), T, '4' (other than
belt removal), '7', or '9'(frozen pump).
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-66-
47 Exhaust Manifold - coded 'A1 or 'B1.
48 Oxygen Sensor - controls the air-fuel mixture going
into the engine of vehicles equipped with three-way
catalytic converters. The sensor is coded '0', '!*,
'2', '4' (unscrewed), or '7'.
49 Carburetor Type - is coded 'F1 (fuel injected), 'A1
(stock carbureted), or 'B' (non-stock carbureted).
Exhaust Gas Recirculation (EGR) System - directs a
portion of the exhaust gases back into the cylinders
to reduce NO emissions in the exhaust gas. The
A
standard EGR configuration consists of a vacuum line
from the carburetor to a sensor (used to detect
engine operating temperature to activate the EGR
valve), and another vacuum line from the sensor to
the EGR valve.
50 EGR Control Valve - coded '0', 'I1, '2', '3', '4',
'7', or '9'.
51 EGR Sensor - coded '0', '!', '2', '3', '5', '71, or '9'.
52 Computer Systems and Related Sensors - computerized
engine and emissions control system which receives
input from various sensors for engine condition
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-67-
information, and constantly adjusts the air/fuel
ratio, distributor, and emissions devices for optimum
economy, driveabi1ity, and emissions. The system
is coded '0', '!', or '6'. This variable includes the
entire computer system except for the oxygen sensor,
which is coded separately (see variable #48, Form A).
Form B - Rear
1-4 ID Number - Same as on Form A.
5-8 Make
9-12 Model
13 Vehicle Type - coded as follows: C = car, T = truck
14-15 License Plate - State abbreviation
16-19 Program Jurisdiction - the city or county of the
vehicle's registration is entered (if the vehicle is
covered by a control program).
20-23 Exhaust gas HC concentration (in ppm) at curb idle.
24-26 Exhaust gas CO concentration (in percent) at curb idle.
27-29 Odometer - mileage in thousands
30 Dash Label - displays the fuel required and is coded
'O'(for leaded vehicles), '!', or '7'.
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-68-
31 Catalytic Converter - oxidizes the HC and CO to water
and COp in the exhaust gas. Later model catalysts
also reduce oxides of nitrogen. The converter is
coded '0', '!', '7' {entire catalyst canister removed),
or 'B' (aftermarket catalyst present).
32 Exhaust System - if as originally equipped an 'A1 is coded
If non-stock a "B1 is coded.
33 Exhaust System Integrity - the condition of the exhaust
system is coded '!' (no obvious leaks) or '9' (leaks
evident).
34 Tank Cap - seals the fuel tank during normal operating
conditions and is coded '!', '7', or '9' (loose cap).
A separate entry is made to indicate whether the tank
cap is stock or non-stock ('A1 or 'B').
35 Tank Label - displays required fuel and is coded '0'
(for leaded vehicles), 'I1, or '7'.
36 Filler Neck Inlet Restrictor - The restrictor is
designed to prevent the introduction of leaded fuel
into a vehicle requiring unleaded fuel. It is coded
'0' (for leaded vehicles), '!', '4' (widened), '6s
(nozzle adaptor present), '7', or 'B1 (non-stock inlet
re stricter-function ing properly).
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-69-
37 Plumbtesmo - Plumbtesmo paper is used to check for the
presence of lead in vehicle exhaust pipes. A positive
indication is coded as 'P1 and a negative as 'N1.
38 Fuel Sample - indicates if inspector was able to obtain
fuel sample for later lead analysis ('Y1 or 'Z').
2. Classification Of Component Conditions
The table below was used to classify the various system
components as tampered (T), arguably tampered (A), or
malfunctioning (M). Only those codes which are applicable
to a given component are listed. Codes for 'not originally
equipped1 and 'functioning properly' are not included in
this table. Refer to Appendix B, Part 1 for an explanation
of the codes.
Codes from forms A and B
Component/system 23456
Dash Label
Tank Cap
Tank Label
Filler Neck Restrictor T T
Catalytic Converter
(cont'd on next page)
7 8 9 B
A
A M
A
T
T
T = tampered
A = arguably tampered
M = malfunctioning
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-70-
Codes from forms A and B
Component/system 2 3
Oxygen Sensor T
PCV System T
Heated Air Intake T
Evaporative Control T
System
Aspirated Air
Injection System
Air Pump Belt
Air Pump System
EGR Control Valve T T
EGR Sensor T T
3. Fuel Sample Collection and
4
T
T
A
T
T
T
T
Label
567
T
T
A
T T T
T
T
T
T
T T
ing Procedures
8 9
M
M
M
M
M
M
M
M
B
T
T
An attempt was made to take a fuel sample from each
vehicle requiring unleaded fuel. These samples were collected
in two-ounce bottles with a hand-operated fuel pump. Once
the sample was drawn, the fuel was replaced with an equivalent
amount of unleaded fuel if the driver requested, and the pump
was flushed with unleaded fuel.
Each bottle was identified with an adhesive label that
nad tne vemcie identifying survey number on it. the venicie
identifying numoer was tne first entry on the data forms
aescrioea in part i of Appendix B. me Dottles were packed,
laDeiea, ana snipped to LHA'S Motor vemcie Lmissions Laboratory
in Ann ArDor according to the snipper's requirements.
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-71-
4. Plumbtesmo Application
1) Clean a portion of the inside of the tailpipe large enough
for the test paper by wiping it out with a paper towel or
cloth. This may be necessary to remove soot deposits
which might mask the color change.
2) Moisten the Plumbtesmo paper with distilled water and
immediately* press firmly against the surface to be tested
for approximately thirty seconds. If the tailpipe is hot
you may wish to clamp the test paper in the tailpipe
using a clean clamp.
*Note: The Plumbtesmo paper must be applied during the
time that the paper is yellow for the reaction to take
place. After approximately 15 seconds the yellow color
disappears and the paper is no longer effective. Excess
water also interferes with the reaction.
Care must be taken to avoid contamination of the test paper
If a person has recently handled a test paper with a
positive reaction, some lead or reactive chemical may
have been transferred to their fingers. Subsequently
handling a clean test paper may cause contamination.
3) After removing the test paper, determine whether a color
change has occurred. Red or pink coloration indicates
the presence of lead.
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-72-
5. Field Quality Control/Assurance
Reference and calibration gases were used to ensure the
accuracy of the emissions analyzer. Horiba gases certified by
RTP were used as reference gases. Two cylinders of reference
gas were used to validate the accuracy of the calibration gases
before they were taken to the field on each survey.
Two calibration gases (Horiba) were used. These gases
were a mixture of CO and HC in nitrogen and were used to check
the instrument at least three times daily. These calibration
gases were certified by the manufacturer and the RTP reference
gases. Their approximate compositions were:
8% CO
1560 ppm HC (Hexane equivalent)
1.6% CO
320 ppm HC {Hexane equivalent)
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-73-
APPENDIX C
EMISSION OUTPOINTS FOR I/M AREAS
The table below lists the emission outpoints used in 1987
by the I/M areas covered in the 1987 tampering survey. The
outpoints for pre-1975 vehicles are not included, since these
vehicles were not surveyed.
Survey Site
Model Year
Emissions Outpoints
CO (%) HC (ppm)
El Paso, TX
Maryl and
(DC Suburbs)
Newark, NJ
Charlotte, NC
Nashville, TN
Atlanta, GA
1975-77
1978
1979
1980
1981
1975-76
1977-78
1979-80
1981 +
1975-80
1981 +
1975-78
1979-80
1981 +
1975-80
1981 +
1975-79
1980
1981 +
7.5
6.5
6.0
4.0
1.2
6.5
5.5
3.5
1.2
3.0
1.2
5.0
3.0
1.2
3.0
1.2
4.0
2.5
1.2
ซ
-
-
-
-
650
550
350
220
300
220
_
-
-
300
220
400
250
220
KEY: CC = catalytic converter (all types), CYL. = cylinder,
OC = oxidation catalytic converter, AI = air injection,
TWC = three way catalytic converter.
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-74-
Survey Site
Spokane, WA
Portland, OR*
Fresno, CA
Model Year
Emissions Outpoints
CO (%) HC (ppm)
1975-78 3.0
1979+(no CC) 3.0
1979 + (CC, 4 cyl .) 2.0
1979 + (CC, 6-8 cyl .) 1.5
1975+ 1.0
1975-79(no CC) 3.5
1975-79(OC, no AI) 4.5
1975-79(OC, AI) 1.5
1975-79(TWC) 1.5
1980+(no CC) 2.5
1980+(OC, no AI) 2.5
1980+(OC, AI) 1.2
1980+(TWC) 1.0
800
600
300
300
225
200
250
150
100
150
150
150
100
* Cutpoints established by model year and make. The
outpoints listed apply to most 1975 and newer vehicles.
KEY: CC = catalytic converter (all types), CYL. =
OC = oxidation catalytic converter, AI = air
TWC = three way catalytic converter.
cyli nder,
injection,
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
JUL 28 1988
OFFICE OF
AIR AND RADIATION
MEMORANDUM
SUBJECT: 1987 Tampering Survey Report Publication
FROM: i. AT Mannato, Chief f .
Regional /State/Local Coordination Section
To: Regional /State/Local Contacts
Recently, our office released the 1987 Motor Vehicle
Tampering Survey. Enclosed is a copy of the survey along
with an accompanying press release. The survey is based on
observations of 7,388 vehicles in fifteen areas around the
c o u n t ry .
The tampering survey details tampering and fuel switching
rates by survey site, vehicle emission component, and Inspection/
Maintenance area (I/M) or non-I/M area for light-duty motor
vehicles and light-duty trucks. Overall, the survey found
that nineteen percent of the 1975 to 1987 model year vehicles
sampled had at least one emission control device tampered
with, and seven percent of the vehicles surveyed had been fuel
switched (fueling with leaded gas in vehicles requiring
unleaded gas).
Tampering rates for each component either stayed the
same or decreased slightly over those in the 1986 survey. The
1986 component specific rates were: catalyst - 4%, Air pump
system 8%, inlet restrictor - 6%, EGR - 6%, evaporative
system - 5%, and PCV - 5%.
The overall tampering rates for light-duty trucks was
slightly lower than for automobiles (17% vs. 19%) in this year's
survey. The reason for the decline in the overall tampering
rate for light duty trucks (LDT's) may be related to the
increase in the number of light duty trucks in the fleet used
as full time transportation and the fact that the majority of
the LDT's tested were 'located in areas covered by some type
of vehicle inspection program. Despite the overall lower
tampering rate for LDT's the most critical components, e.g.
catalytic converters, are still tampered with more frequently
on trucks than on automobiles.
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-2-
The survey also discusses the effectiveness of I/M
testing In Identifying tampered vehicles. CO and HC Idle
failure rates are significantly higher for tampered vehicles.
However, one-third of all tampered or fuel switched vehicles
in the survey were still able to pass an idle emissions test.
This suggests that idle emissions testing may not be an effec-
tive strategy for identifying tampering and fuel switching.
Most, if not all, of those tampered and fuel switched vehicles
that fail an idle test would probably not be required to
replace their catalysts in order to pass the test.
Past surveys have shown tampering increases with the age of
the vehicle. But for those vehicles covered by an I/M and/or
antitampering program our survey shows the rate of tampering
is significantly lower than for those vehicles surveyed in an
area without a program. Even vehicles as new as 3 years old
have lower rates in an inspection program area than an area
without one.
If you have any questions concerning the enclosed report,
feel free to call me or Bob Greco at (202) 382-2640.
Enclosures
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