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!

 

When was your last tuned up (new plugs & wires) ? Ever used seafoam? I'd swap out the new O2 with a junk yard item before using sea foam, just to be safe.

 

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.