Failed smog test
10-10-2010, 05:38 PM
#1
Cruising
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Failed smog test
I"ve have a 1991 for the last 2 years that just failed its California smog test. During the test the car started to overheat which was odd. Never had that problem before. Found radiator core clogged. Thought maybe because of the heat, the car failed. I also want to replace plugs for best emmissions performance. Will any of these things help or is the cat. converter gone. Any advice will help.
Mark
Mark
10-10-2010, 07:07 PM
#2
Corvette Junkie
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2023 C7 of the Year Finalist - Unmodified
I"ve have a 1991 for the last 2 years that just failed its California smog test. During the test the car started to overheat which was odd. Never had that problem before. Found radiator core clogged. Thought maybe because of the heat, the car failed. I also want to replace plugs for best emmissions performance. Will any of these things help or is the cat. converter gone. Any advice will help.
Mark
Mark
10-10-2010, 11:10 PM
#3
Safety Car
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The first thing to do before any emissions test is to do a Complete tune up or at the very least change the spark plugs, oil, oil filter, air filter, and check the timing.
If you don't know the last time a tune up has been done, now is the time.
If you don't know the last time a tune up has been done, now is the time.
10-10-2010, 11:21 PM
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St. Jude Donor '05
Post up a sheet before buying anything
10-11-2010, 02:00 PM
#6
Cruising
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Failed the emission test at both 15 mph and 25 mph.The results for 25 mph are below.
%C02 MEAS was 12.4
%02 MEAS was 3.1
HC (PPM) was MAX 61 AVE 19 MEAS 101
C0 (%) was MAX 0.42 AVE 0.06 MEAS 0.27
NO (PPM) was MAX 502 AVE 189 MEAS 1449
Hope this helps. Thanks
%C02 MEAS was 12.4
%02 MEAS was 3.1
HC (PPM) was MAX 61 AVE 19 MEAS 101
C0 (%) was MAX 0.42 AVE 0.06 MEAS 0.27
NO (PPM) was MAX 502 AVE 189 MEAS 1449
Hope this helps. Thanks
Last edited by pfsrst2; 10-11-2010 at 02:06 PM. Reason: Did not display right
10-11-2010, 04:04 PM
#7
Melting Slicks
high HC's, unburned hydrocarbons; try a complete ignition tune up first; rotor, rotor cap, spark plug wires, spark plugs.
high NOX, make sure egr valve works, all egr passages clear, and all vacumn hoses intact and hooked up.
only then would I look at the cats.
high NOX, make sure egr valve works, all egr passages clear, and all vacumn hoses intact and hooked up.
only then would I look at the cats.
10-11-2010, 04:08 PM
#8
Le Mans Master
With that NOX #, the EGR isn't working and it should be spitting out a 32 or something similar and a Check Engine Light should be staring you in the face. Without EGR, it will heat up and then dump fuel.
I scan a car before I do anything as if fuel delivery is right and it doesn't pass, you can generally count on a new CAT. Given your high HC's that may be the case but you want to fix the EGR first.
I scan a car before I do anything as if fuel delivery is right and it doesn't pass, you can generally count on a new CAT. Given your high HC's that may be the case but you want to fix the EGR first.
10-11-2010, 04:27 PM
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High HC = poor air/fuel ratio. (most likely a bad O2 sensor and general tune up)
High NOX= high combustion temperatures. (most likely a malfunctioning EGR valve, check for code 32)
High NOX= high combustion temperatures. (most likely a malfunctioning EGR valve, check for code 32)
