failed emissions

[Mr. Sinister]

High CO means bad cat or the cat wasn't warm enough yet. Bad EGR would increase NOx, but they don't care about that in IL. I would:

- check for vacuum leaks
- check timing
- change plugs if they're old
- change oil if it's old
- change air filter if it's old

If the car is stock, it should pass with no problems if everything is working the way it should be.

 

[mrnickleye]

Engine coolant temp (thermostat) must be at like 180* and above. The coolant sensor for the computer can be inaccurate and cause the computer to think the engine is colder than it really is, and it will richen the mixture.

Also the AFM malfunctioning can cause you to run rich.

But if the CO% came down with the new 02 sensor, and all the #s are pretty close, then a new cat may just bring them on down.

I know that many smog techs will not help you along (fro free) because they make a living diagnosing and repairing these problems.

 

[rolman]

Ask the person at inpection station to do a "two step inspection. Legally they can do that if the car has limited slip differential. I have had that do on my 92 in order to pass at Jiffy Lube.

 

[jetjock]

Again, what mr nickleye said. Seems he knows his smog stuff pretty well.

High CO is indicative of a rich mixture. The converter may bring it down if it's not too high but it's life will be impacted. The cat only works best if the composition of the exhaust stream is kept within a narrow range. This is the sole purpose of the O2 sensor. NOx is handled by a different portion of the cat as long as the EGR keeps it within limits. That said, NOx is also dependant on the lambda system working correctly.

Induction leaks would cause a lean mixture and low CO. Changing oil will bring down HC but won't do squat for CO. The remainder of the advice given in the post above is valid.

 

[huntin5L]

Well i forgot to update this thread, but i passed emissions with the new 02, but.....I just barely passed, it still is running rich for some reason. I posted another thread about spark plug change that has some new issues that arose.

 

[bluemax]

You should check for old leaking or cracked intake lines and replace as necessary. Also, if you have an old cat., you should change it. Cats don't last forever.