I failed emissions with my B18C5 ('98) EG. Other than an AEM intake the engine is stock and has never been opened. I put like ~2000 miles on this car a year, basically driving it to track and on track.

Pretty much everyone has told me to replace my O2 sensors -- but they are big $$. Do I need to replace both sensors or just one (which one, in front of or behind the cat)? I was thinking of getting one (or two if need be) from Autozone, installing it, passing the test, then shelving it for next year. This car is fully OBDII, with no check engine light.

To try and pass, I've:
- changed my oil (Mobile1 5-30)
- ordered new plugs and wires (NGK-PFR6G-11(5555) and NGK-HE64(8018))
- reset ECU
- run it HOT before the test


Try #1
HC ppm - 297 (136 allowed-FAILED)
CO % - 1.51 (.76 allowed-FAILED)
NOx ppm - 653 (984 allowed-PASSED)

Try #2
HC ppm - 137 (136 allowed-FAILED)
CO % - 1.05 (.76 allowed-FAILED)
NOx ppm - 91 (984 allowed-PASSED)

So I guess I'm failing mostly due to CO. What would cause this, and what would you do to fix? (I've searched, but so far I haven't found an answer).

TIA -e



Modified by SpiceyRice at 10:58 PM 8/27/2003

 

I think I'm running rich, which explains why my back bumper is filthy! ...but since this is a track car, and sees lots of high RPMs while very HOT, I want it to be rich. It's stock, so I haven't done anything to make it more/less rich. Why is such a well tuned engine running so rich and is it bad?

What else should I try - cleaning fuel injectors? anything else?

I found some stuff useful for future searchers.
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CO is typically created when there isn't enough O (oxygen) left over after/during combustion to create CO2. This can be caused by a rich condition, but is typically accompanied by higher HC.
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A great deal of the CO is created by the oil (carbon based unless you use synthetic) and crank case vapors (blow by). Have you tried changing your oil just before the test with new spark plugs. It worked for me.
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If you have none of the emmission controls connected I suggest you connect a few. You should at least try a new breather and pvc valve to expel some of the vapors.



Modified by SpiceyRice at 9:11 PM 8/27/2003