failed emissions in TX, need advice

[MYK]

I just went to get my car inspected and it failed. I did a search and I have a pretty good idea that it may be an O2 sensor. my car is a 92 dohc, no power mods. I just did new plugs, cap, rotor, wires, air filter. The car seems to be running rich. It used to misifre/stumble pretty bad during accleration before the new parts. now it seems to run fine but doesn't seem to want to rev very smoothly. and now it failed emissions. my HC numbers at low speed (15mpg/1911 rpms) were 144 vs 136 passing. and my CO numbers were 1.87 vs .76 passing. at high speed (25mph/950 rpms) the CO failed with a reading of 1.02 vs .73 passing. all my other numbers were fine. NOx was way under the limit so I'm guessing its not an egr problem. am I right in suspecting the O2 sensor? it's about the only thing, other than the fuel filter I have yet to change. car has 127k on it BTW

myk

[Dammitboy]

try a new cat.

[DAEDALUS]

Of all the blind solutions the cat is probably the most expensive option. Save that one for last or at least till a little more is known.Definitely looks rich still. The extra gas is why HC is high, and also by CO is high, since there's not enough O2 to create CO2, so CO gets created in the burn. Also, slow rev is another sign.If you're sure it's not misfiring then it could be an injector leak, a bad O2, or a bad temp sensor/connector, just to name a few. I don't think a bad O2 by itself could cause a failure, but I'm not certain. You could measure the voltage and see if it dances up and down past .45V.

[MYK]

yeah I've been reading through my FSM and will do some checks tomorrow after work with my meter and also see if the ECM has any stored codes. I don't really want to replace the cat....but I guess I could if I had too. and might as well do a brm exhuast while I'm at it