77-1 AW
The Effects of Emission Control System Malfunctions
or Maladjustments on Exhaust Emissions
October 1976
Technology Assessment and Evaluation Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
U.S. Environmental Protection Agency
-------
Background
The Environmental Protection Agency is currently undertaking programs
that measure the exhaust emissions of in-use vehicles. One of these
programs, the Emission Factors Program (EFP), has generated data indi-
cating that a high percentage of in-use 1975 automobiles have exhaust
emissions exceeding the Federal emission standards for 1975-76 light-
duty vehicles.
Typical failing vehicles have very high CO emissions. High CO emissions
may be indicative of improper adjustment of either the idle mixture or
the choke. Since idle mixture and choke adjustments are easily acces-
sible and adjusted on most cars, it seems probable that the maladjust-
ment of these two items may be responsible for some of the high emission
levels measured in the EFP.
In prder to further investigate these possibilities, a test program was
conducted by the EPA to quantify the effects of various engine mal-
adjustments on exhaust emissions. This test program would help identify
maladjustments resulting in the types of failures encountered in the
EFP. .
The results and conclusions of the EPA test program are set forth in
this report. The conclusions from the EPA tests can be considered
quantitatively valid only for the specific type of vehicle used in the
EPA test program, although it is reasonable to extrapolate the results
from the EPA tests to other types of vehicles in a directional or quali-
tative manner, i.e., to suggest that similar results are likely to be
achieved on other types of vehicles. However, tests on such other vehicles
would be required to reliably quantify results on other types of vehicles.
Test Vehicle Description
Because Chrysler Corporation has an idle CO specification, and because
idle CO is an easy quantifier of idle mixture adjustment, a request was
made of Chrysler to supply a test vehicle for use in this program.
Chrysler agreed to supply a vehicle, and made available a 1976 Dodge
Coronet station wagon equipped with a 360 cu in. engine and automatic
transmission.
At the time of delivery to the EPA, the test vehicle was fresh from the
assembly line and had been driven only 50 miles. By the end of the test
program about 1100 miles had been accumulated on the vehicle.
A listing of pertinent vehicle statistics is given on the Vehicle In-
formation Sheet at the end of this report.
-------
Test Program
Exhaust emission and fuel economy tests were conducted in accordance
with the 1975 Federal Test Procedure ('75 FTP) for light-duty vehicles
(Federal Register, June 30, 1975, Vol. 40 No. 126, Part III). Evapora1-
tive emissions were not measured.
A total of fourteen different vehicle maladjustments were investigated
during the test program. The following table lists the maladjustments
and the order in which they occurred.
Table I
Test Program
1. As received test.
2. Adjust to manufacturer's specifications for baseline
test.
3. Carburetor-maladjustments
a) adjust idle mixture for "smoothest idle"
(1.7% idle CO).
b) adjust idle mixture to 2.9% idle CO.
c) adjust idle mixture to 5.6% idle CO.
d) readjust to baseline.
e) disconnect choke electric heating element.
f) disconnect choke linkage.
4. Disconnect EGR vacuum line.
5. Check baseline.
6* Timing maladjustments
a) 5 retard from baseline.
b) 10 retard from baseline.
c) 5 advance from baseline.
d) 8 advance from baseline.
e) Baseline (6° BTDC)
7. Disconnect one sparkplug wire.
8. Check baseline.
9. Apply full manifold vacuum to the distributor
vacuum advance.
10. Number 9 above', plus 5° timing advance from baseline
and the EGR vacuum line disconnected.
11. Check baseline.
12. Disconnect choke vacuum break.
-------
Duplicate tests were conducted at each maladjustment. The maladjust-
ments were not cumulative, i.e., after completing a given maladjustment
test, the vehicle was restored to baseline before proceeding to the next
test point.
Test Results
Table II summarizes the exhaust emissions and fuel economy measured at
each maladjustment. The average of all tests conducted at each condition
is presented.
Table II
1975 Federal Test Procedure
mass emissions in
grams per mile
Test
Configuration HC CO NOx miles/gal.
As received 0.30 4.9 2.46 11.0
Baseline (.3% CO) 0.41 7.9 2.22 10.6
Smooth idle (1.7% CO) 0.96 21.1 2.01 10.6
2.9% idle CO 0.99 27.7 1.94 10.4
5.6% idle CO 1.84 65.2 1.66 10.2
Baseline 0.30 5.8 "2.13 10.7
Electric choke disconnected 0.43 11.6 1.93 10.8
Disconnect choke linkage 0.39 5.0 2.04 10.9
Disconnect EGR line 0.43 3.8 3.69 11.6
Baseline 0.29 5.0 2.07 10.9
5° retard 0.34 8.6 1.93 9.9
10° retard 0.49 20.6 1.85 8.0
5° advance 0.35 4.8 2.35 11.3
8° advance 0.44 7.0 2.69 11.3
Baseline 0.33 7.0 2.25 10.7
Disconnect sparkplug wire 4.21 7.1 2.73 9.9
Baseline 0.40 6.4 2.42 10.8
Manifold vacuum spark advance 0.55 6.5 2.20 11.9
Manifold vacuum spark advance,5
advance, No EGR 0.59 5.4 5.89 12.5
Baseline 0.41 6.7 2.46 11.0
Choke vacuum break disconnected 1.95 17.3 2.27 10.8
1975-76 Emission standards 1.5 15.0 3.1
-------
Details;of individual tests are presented in Tables VII and VIII following
the text of this report.
The manufacturer's idle CO specification for the Dodge test vehicle is
0.3% (+.4% - .3%). This is typical of the idle CO setting that Chrysler
uses for most of its engine families. Chrysler vehicles tested during
the EFP have been classified according to idle CO emissions. Vehicles
are classified as having either less than 0.5% idle CO or greater than
0.5% idle CO. Chrysler vehicles in the EFP with idle CO above 0.5%
and exhaust emissions levels exceeding the '75-'76 standards, had an
average idle CO of 4.1%. Table III compares the emissions of these EFP
vehicles to the Dodge test vehicle when adjusted to 2.9% and 5.6% CO.
Table III
'75 FTP mass emissions
in grams per mile
average
HC CO NOx idle CO
EFP vehicles 1.9 54.0 2.4 4.1%
Dodge test vehicle 0.99 27.7 1.94 2.9%
Dodge test vehicle 1.84 65.2 1.66 5.6%
The data indicate that improper idle mixture adjustment could account
for some of the high CO emissions in EFP. However, some of the Chrysler
EFP vehicles with idle CO below 0.5% still failed to meet the '75-75 CO
emission levels. Two simulated maladjustments of the Dodge test vehicle
resulted in idle CO below 0.5% and CO emissions exceeding emission
standards. The two maladjustments were the 10 timing retard and dis-
connecting the choke vacuum break. Table IV compares the emissions of
EFP vehicles with less than 0.5% idle CO to the emissions of the Dodge
test vehicle at these two maladjustments.
Table IV
'75 FTP mass emissions
in grams per mile
i
average
HC CO NOx idle CO
EFP vehicles 1.3 23.5 2.5 0.1%
Dodge - 10° retard 0.49 20.6 1.85 0.1%
Dodge - choke vacuum 1.95 17.3 2.27 0.3%
break disconnected
-------
Further information on the effects of maladjustments on emissions can be
obtained from the data by examining the CO emissions during the three
segments of the '75 FTP. Table V contains individual bag CO data for
the EFP vehicles. Table VI contains similar data for the Dodge test
vehicle.
Table VI
'75 FTP CO bag data
Dodge Test Vehicle
grams per mile
As received
Baseline
Smooth idle
2.9% idle CO
5.6% idle CO
Baseline
Electric choke disconnected
Disconnect choke linkage
Disconnect EGR line
Baseline
5 retard
10° retard
5 advance
8 advance
Baseline
Disconnect sparkplug wire
Baseline
Manifold vacuum spark advance
Manifold vacuum spark advance
5° advance, No EGR
Baseline
Vacuum break disconnected
Bag 1
Bag 2
Bag 3
18.3
26.6
34.7
38.2
61.5
23.3
51.1
16.7
15.0
20.2
31.1
59.3
19.5
28.7
29.2
26.8
25.9
26.8
23.4
26.9
78.4
1.0
2.4
20.2
29.1
79.9
0.7
0.5
1.1
0.3
0.4
1.3
8.3
0.6
1.2
0.6
0.8
0.4
0.8
0.5
1.0
.1.1
2.3
4.3
12.7
17.1
40,1
2.4
3.0
3.7
2.1
2.4
5.5
15.0
1.5
1.8
2.3
4.4
3.2
2.4
1.3
2.2
2.3
Bag 1
93.5
78.9
Table V
'75 FTP CO bag data
EFP vehicles
grams per mile
Bag 2
5.2
56.0
Bag 3
5.6
31.4
idle CO
<0.5% >0.5%
x
X
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Tables V and VI reinforce the hypothesis that carburetor maladjustments
account for a portion of the failed vehicles encountered in the EFP.
Other than idle circuit maladjustment, only the 10 retard caused con-
sistently high CO emissions in all three portions of the '75 FTP.
Conclusions
The data collected during the test program support the hypothesis that
idle mixture maladjustment may be a major cause of high exhaust emis-
sions from in-use vehicles. The reasons for idle mixture maladjustments
are less easy to identify. Two likely possibilities are improper assembly
and/or improper vehicle adjustments in the field. However, identifying
the causes of the maladjustments is beyond the scope of this test program.
Further testing is to be carried out by the EPA to investigate the
effects of vehicle maladjustments on vehicles produced by manufacturers
other than Chrysler. The results of such testing will be presented in
subsequent EPA reports.
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Table VII
1975 Federal Test Procedure
mass emissions in
grams per mile
Test #
HC
CO
CO,
NO
miles/gal.
As received
77-2255
Baseline
77-2276
77-2277
Smooth idle
77-2355
77-2356
2.9% idle CO
77-2415
77-2416
5.6% idle CO
77-2599
77-2630
Baseline
77-2716
0.30
0.43
0.39
0.93
0.99
1.00
0.97
1.83
1.85
0.30
4.9
8.3
7.5
21.2
21.0
27.5
27.9
65.2
65.2
5.8
797.
827.
824.
796.
816.
806.
816.
768.
764.
821.
2.46
2.21
2.22
1.99
2.02
1.98
1.90
1.69
1.63
2.13
11.0
10.5
10.6
10.7
10.4
10.4
10.3
10.1
10.2
10.7
Electric choke
assist disconnected
77-2766
77-2767
Disconnect
77-2869
77-2870
Disconnect
77-3082
77-3147
Baseline
77-3188
5 retard
77-3238
77-3239
0.40
0.45
choke linkage
0.44
0.33
EGR line
0.32
0.54
0.29
0.36
0.31
11.2
12.0
5.1
4.9
3.3
4.3
5.0
9.1
8.0
803.
801.
823.
800.
753.
762.
803.
894.
878.
1.96
1.89
2.00
2.07
3.55
3.82
2.07
1.93
10.8
10.8
10.7
11.0
11.7
11.5
10.9
9.8
10.0
-------
8
Table VII con't.
Test #
10° retard
77-3378
77-3379
5 advance
77-3544
77-3545
8 advance
77-3546
77-3606
Baseline
77-3607
77-3778
Disconnect spark
77-3779
77-3825
Baseline
77-3827
77-3882
Manifold vacuum
77-3912
77-3913
Manifold vacuum
77-3936
77-3991
Baseline
77-3937
77-4050
HC
0.44
0.53
0.36
0.33
0.37
0.51
0.34
0.32
plug wire
3.99
4.42
0.38
0.41
spark advance
0.54
0.56
spark advance,
0.57
0.61
0.39
0.42
Vacuum break disconnected
77-4109 2.04
77-4171 1.85
CO
20.2
21.0
3.8
5.8
6.0
8.0
7.0
6.9
7.1
7.0
6.3
6.4
6.7
6.3
5 advance,
4.9
5.9
6.6
6.7
17.6
17.0
co2
1090
1064
769.
782.
774.
774.
819.
814.
874.
876.
815.
805.
743.
728.
No EGR
703.
697.
791.
806.
804.
775.
NO
1.90
1.80
2.31
2.38
2.68
2.69
2.26
2.24
2.70
2.75
2.44
2.40
1.64
2.75
5.93
5.84
2.54
2.38
2.26
2.28
miles/gal,
7.9
8.1
11.4
11.2
11.3
11.3
10.7
10.7
9.9
9.8
10.7
10.9
11.7
12.0
12.5
12.5
11.1
10.8
10.6
11.0
-------
Test #
Table VIII
'75 FTP bag emissions in grams per mile
Bag 1: Cold Transient
HC NO CO,
Bag 2: Stabilized
CO MPG HC NO
x
CO,, CO MPG
Bag 3: Hot Transient
HC NO
CO,, CO
MPG
As received
77-2255
Baseline
77-2276
77-2277
Smooth idle
77-2355
77-2356
2.9% idle CO
77-2415
77-2416
5.6% idle CO
77-2599
77-2630
Baseline
77-2716
Electric choke
77-2766
77-2767
1.04
1.43
1.30
1.91
2.27
1.86
1.81
2.68
2.61
1.08
2.96
2.69
2.72
2.43
2.56
2.53
2.39
2.17
2.12
2.48
812.
848.
852.
816.
840.
834.
836.
813.
811.
854.
assist disconnected
1.52 1.77 786.
1.70 1.64 792.
Disconnect choke linkage
77-2869 1.52
77-2870 1.16
Disconnect EGR
77-3082
77-3147
Baseline
77-3188
line
1.13
2.07
0.96
2.42
2.43
4.16
4.41
2.42
873.
863.
770.
795.
815.
18.3
27.5
25.7
36.2
33.2
37.5
38.9
61.5
61.5
23.3
49.6
52.6
16.9
16.4
13.2
16.8
20.2
10.5
9.9
9.9
10.1
9.9
9.9
9.8
9.7
9.7
9.9 .
10.2
10.1
9.8
9.9
11.2
10.7
10.4
0.08
0.12
0.11
0.72
0.67
0.80
0.75
1,81
1.83
0.07
0.08
0.08
0.09
0.07
0.07
0.09
0.08
1.80
1.62
1.66
1.42
1.45
1.38
1.30
1.10
1.10
1.67
1.68
1.59
1.56
1.68
2.73
3.16
1.59
830.
859.
855.
821.
843.
830.
842.
774.
773.
846.
843.
836.
843.
810.
784.
781.
839.
1.0
2.8
2.0
20;1
20.3
29.1
29.1
80.3
79.5
0.7
0.2
0.8
1.3
0.8
0.3
0.3
0.4
10.7
10.3
10.3
10.4
10.1
10.1
10. 0
9.8
9.8
10.5
10.5
10.6
10.5
10.9
11.3
11.3
10.6
0.16
0,25
0.25
0.60
0.64
0.74
0.76
1.25
1.31
0.15
0.18
0.12
0.30
0.18
0.18
0.25
0.18
3.36
2.99
2.89
2.73
2.71
2.72
2.67
2.46
2.29
2.75
2.64
2.63
2.53
2.53
4.66
4.63
2.73
724.
750.
744.
733.
747.
739.
749.
723.
711.
749.
738.
742.
749.
732.
683.
702.
726.
2.3
4.4
4.1
12.1
13.2
16.9
17.3
39.2
40.9
2.4
3.4
2.6
3.4
3.9
1.7
2.5
2.4
12.2
11.7
11.8
11.8
11.5
11.6
11.4
11.3
11.4
11.8
11.9
11.9
11.7
12.0
12.9
12.6
12.1
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Table VIII con't
Bag 1: Cold Transient
Bag 2: Stabilized
Bag 3: Hot Transient
Test //
5 retard
77-3238
77-3239
10° retard
77-3378
77-3379
5 advance
77-3544
77-3545
8 advance
77-3546
77-3606
Baseline
77-3607
77-3778
Disconnect
77-3779
77-3825
Baseline
77-3827
77-3882
1
1
1
1
1
1
1
1
1
1
spark
9
11
1
1
Manifold vacuum
77-3912
77-3913
1
1
Manifold vacuum
77-3936
77-3991
1
1
HC
.16
.04
.59
.74
.24
.15
.30
.64
.16
.17
plug
.64
.28
.19
.37
spark
.64
.69
spark
.73
.81
NO
X
2.15
-
2.24
1.99
2.77
2.79
3.11
3.21
2.51
2.54
wire
2.89
2.94
2.74
2.78
advance
3.19
2.95
advance ,
6.57
6.35
C00
2
992.
902.
1120.
1088.
789.
796.
792.
795.
868.
841.
898.
911.
848.
837.
795.
777.
CO
33.1
29.0
57.6
60.9
14.5
24.9
26.5
30.8
29.0
29.3
27.9
25.6
25.2
26.5
26.9
26.6
MPG
9.1
9.3
7.3
7.5
10.9
10.6
10.6
10.5
9.7
10.0
9.1
9.0
10.0
10.0
10.5
10.8
HC
0.06
0.07
0.07
0.21
0.10
0.09
0.11
0.13
0.08
0.08
1.81
1.94
0.09
0.10
0-.17
0.25
NO
X
1.64
1.62
1.65
1.58
1.74
1.82
2.09
2.12
1.88
1.79
2.32
2.32
2.02
1.93
1.11
2.42
C00
2
935.
-924.
1148.
1127
798.
815.
803.
801.
841.
844.
895.
897.
836.
824.
744.
729.
CO
i.6
1.0
8.2
8.4
0.7
0.5
0.6
1.7
0.6
0.6
0.7
0.8
0.5
0.3
0.8
0.7
MPG
9.5
9.6
7.6
7.8
11.1
10.9
11.0
11.0
10.5
10.5
9.8
9.8
10.6
10.8
11.9
12.1
5° advance, No EGR
736.
737.
21.7
25.0
11.4
11.3
0.21
0.22
5.02
5.14
712.
704.
0.3
0.7
12.4
12.6
HC
NO
CO,
CO
MPG
0.31
0.22
0.26
0.23
0.20
0.16
0.17
0.38
0.21
0.15
3.88
3.97
0.32
0.29
0.43
0.29
0.38
0.46
2.30
2.13
2.08
3.04
3.13
3.50
3.41
2.82
2.88
3.28
3.41
3.01
3.01
1.48
3.23
7.18
6.80
794.
772.
956.
927.
698.
706.
705.
705.
740.
738.
8J.5.
807.
751.
744.
701.
688.
662.
655.
5.2
5.7
15.0
15.0
1.6
1.4
0.9
2.7
2.7
1.9
3.8
5.0
3.3
3.1
3.0
1.8
1.0
1.5
11.0
11.3
9.1
9.3
12.7
12.5
12.6
12.5
11.9
12.0
10.7
10.7
11.7
11.8
12.5
12.8
13.3
13.5
-------
Table VIII con't
Test #
Baseline
77-3937
77-4050
Bag 1: Cold Transient
HC
1.37
1.52
NO.
2.99
2.90
CO,
802.
831.
CO
26.6
27.1
MPG
10.5
10.1
Bag 2: Stabilized
HC
0.10
0.10
NO
x
2.02
1.86
CO,
821.
832.
CO
1.1
0.9
MPG
10.8
10.6
Vacuum break disconnected
77-4109 9.11 2.57 803. 78.7 9.3 0.13 1.82 836. 1.2 10.6
77-4171 8.48 2.55 757. 78.1 9.8 0.11 1.86 811. 1.0 10.9
Bag 3: Hot Transient
HC
NO
CO,
0.19 3.21 725.
0.19 2.98 737.
CO
2.0
2.3
MPG
12.2
12.0
0.34 2.87 744. 2.8 11.8
0.17 2.89 719. 1.7 12.3
-------
12
TEST VEHICLE DESCRIPTION
Chassis model year/make - 1976 Dodge Coronet Wagon
'Emission control system - EM/EGR/CAT
Engine
type 4 stroke, Otto cycle, V-8, ohv
bore x stroke 4.00 x 3.58 in./101.6 x 90.9 mm
displacement 360 cu in./5900 cc
compression ratio 8.4:1
maximum power @ rpm ....... 170 net hp/127kW at 4000 rpm
fuel metering 2 barrel carburetor
fuel requirement unleaded
Drive Train
transmission type -. . 3 speed automatic
final drive ratio . ... .... 3.23:1
Chassis
type front engine, rear wheel drive
tire size • HR78 x 15
curb weight . . . 4705 lb./2134 kg
inertia weight ;. 5000 Ib
passenger capacity 8
Emission Control System
basic type EM/EGR/CAT
oxidation catalyst location. . . . Underseat
EGR type ported, venturi vacuum amplified
durability accumulated on system . 1000 mi./1600 km
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