96 SOHC will not pass smog, high HC's any ideas?
#1
12-08-2010, 08:33 PM
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96 SOHC will not pass smog, high HC's any ideas?
Hi,
I have a 96 SOHC Neon that has trouble passing the smog.
The 1st time it passed the emmisions, but failed the test when attached to the OBDII port. I had reset the codes, but hadn’t driven enough to reset the emmisions monitors
I had a persistant P0134 code, so I replaced the upstream O2 sensor with a BOSCH OEM sensor, that cured the P0134 code.
The 2nd test it failed on the HC at 25mph
The values I’m getting are
15mph
HC Measured = 64ppm (max = 66ppm, ave = 9ppm)
CO Measured = 0.18% (max = 0.57%, ave = 0.02%)
HC Measured = 485ppm (max = 487ppm, ave = 57ppm)
25mph
HC Measured = 50ppm (max = 49ppm, ave = 7ppm) FAIL
CO Measured = 0.15% (max = 0.55%, ave = 0.03%)
HC Measured = 373ppm (max = 774ppm, ave = 50ppm)
I decided to retest after a long drive to get it really warm, it failed the 3rd retest. The values are
15mph
HC Measured = 56ppm (max = 66ppm, ave = 9ppm)
CO Measured = 0.17% (max = 0.57%, ave = 0.02%)
HC Measured = 477ppm (max = 487ppm, ave = 57ppm)
25mph
HC Measured = 54ppm (max = 49ppm, ave = 7ppm) FAIL
CO Measured = 0.15% (max = 0.55%, ave = 0.03%)
HC Measured = 372ppm (max = 774ppm, ave = 50ppm)
I pulled the plugs after the 3rd retest and they were completely shot. I replaced the plugs with Bosch Super Plus plugs gapped at .035in.
I took the car back to get the car retested, the Smog guy told me not to waste my time, he said likely the CAT is bad. I should probably insisted on the retest, but was pretty annoyed at the guy.
Any ideas? Right now I don’t have a job, so don’t want to invest in a new CAT if I don’t have to. Is there an easy way to drop the HC’s down?
Thanks in advance for any help!
I have a 96 SOHC Neon that has trouble passing the smog.
The 1st time it passed the emmisions, but failed the test when attached to the OBDII port. I had reset the codes, but hadn’t driven enough to reset the emmisions monitors
I had a persistant P0134 code, so I replaced the upstream O2 sensor with a BOSCH OEM sensor, that cured the P0134 code.
The 2nd test it failed on the HC at 25mph
The values I’m getting are
15mph
HC Measured = 64ppm (max = 66ppm, ave = 9ppm)
CO Measured = 0.18% (max = 0.57%, ave = 0.02%)
HC Measured = 485ppm (max = 487ppm, ave = 57ppm)
25mph
HC Measured = 50ppm (max = 49ppm, ave = 7ppm) FAIL
CO Measured = 0.15% (max = 0.55%, ave = 0.03%)
HC Measured = 373ppm (max = 774ppm, ave = 50ppm)
I decided to retest after a long drive to get it really warm, it failed the 3rd retest. The values are
15mph
HC Measured = 56ppm (max = 66ppm, ave = 9ppm)
CO Measured = 0.17% (max = 0.57%, ave = 0.02%)
HC Measured = 477ppm (max = 487ppm, ave = 57ppm)
25mph
HC Measured = 54ppm (max = 49ppm, ave = 7ppm) FAIL
CO Measured = 0.15% (max = 0.55%, ave = 0.03%)
HC Measured = 372ppm (max = 774ppm, ave = 50ppm)
I pulled the plugs after the 3rd retest and they were completely shot. I replaced the plugs with Bosch Super Plus plugs gapped at .035in.
I took the car back to get the car retested, the Smog guy told me not to waste my time, he said likely the CAT is bad. I should probably insisted on the retest, but was pretty annoyed at the guy.
Any ideas? Right now I don’t have a job, so don’t want to invest in a new CAT if I don’t have to. Is there an easy way to drop the HC’s down?
Thanks in advance for any help!
#2
12-11-2010, 11:50 AM
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#3
12-13-2010, 01:38 PM
high HC is unburnt fuel left over in the exhaust. either you have a missfire orthe cat is not burning it all up. Check ignition system thouroughly (plugs , wires, even make sure no oil has leaked in around the plug tubes, this can cause a miss).
Always test with Clean oil in the engine and the cat up to temps.
you'll be blown away at the test results after putting on a new cat, clean as a whistle, if theres no missfire I'm gonna have to agree with the guy who pissed you off that it is the CAT. especially since your really close to the limits.
Always test with Clean oil in the engine and the cat up to temps.
you'll be blown away at the test results after putting on a new cat, clean as a whistle, if theres no missfire I'm gonna have to agree with the guy who pissed you off that it is the CAT. especially since your really close to the limits.