hmm, I still have high NOx, so, I guess that even though I was finally able to get my check engine light to go away that my EGR is still not functioning perfectly. oh well though, guess I don't have to worry about it for another 2 years

Two years? I thought Cali was tough? Houston has the same emisions standards but we have to do it every year.

It's probably your cat and not your EGR.
The cat takes Oxygen from NOx and adds it to the CO to make CO2, N and O2.
If you look your CO is high too....

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good point. oh well, I'm hoping to go with one or two magnaflow cats when I go turbo. (probably just one, since I know I probably won't be passing smog no matter how many cats I put on it after that. lol)

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No no. The cat is the last part of the emission matrix you should even consider to do a proper repair. The EGR's primary function is to reduce NOx and since you already know you're egr is not functioning properly, then that's what you need to repair. I have conducted experiments on this by testing my car with the egr connected and disconnected. The differences in NOx was about 400 ppm. And by looking at your CO2 and O2 readings, it seems as if your cat is still reducing efficiently.


LOL Hey 6strngs... I live about 30-40 minutes from you.

This post has been edited by Celicaguy13: Mar 27, 2007 - 9:35 AM

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well, the thing is, my car threw a check engine light for the EGR, and I replaced the EGR valve and vacuum module, and did ALOT of cleaning of the tubes and passageways and it made the CEL go away, but I still have high NOx. So, if it was something to do with the EGR, I wouldn't even begin to know where to look. but, if the cat is clogged, it could explain the NOx and the somewhat high (though still acceptable) CO2

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It might be the last, but that doesn't mean you shouldn't consider it...
The cat also converts NOx as well as HC and CO. It's a THREE way cat.
For example, my truck has a welded shut EGR. And it passed NOx with flying colors [we have the same emissions standards as you].

Your cat probably isnt' clogged.
And I doubt it's toast yet. If it was you would probably have a P0420 code.
The only way to know for sure is to look at the car. I can't tell how well you cleaned out the EGR, or the actual condition of the cat from 3000 miles away. :shrug:

like I said, it doesn't really matter for another 2 years. plus the whole exhaust system will be taken off the car pretty soon anyway, maybe when I have to switch back to stock for a smog check in 2 years I'll replace the cat before I go.

Well I wasn't implying that EGR was the only possible cause of a NOx failure. You probably just have a high mileage engine with a bunch of carbon buildup on your pistons. That carbon buildup is the main cause of Nox, but not the only possible culprit.