StuntDiabetic

As I said, my 2002 A4 1.8t (AMB I believe) failed an emissions test today with too high of NOx, limit is 1.5, my reading was 1.6813. Everything else was fine. The last time my Mechanic looked at it for something else he said he had cleared a code for bad O2 sensors. I haven't had a CEL since but am thinking If I replace the sensors i might pass? any thoughts? advice? I realize I have neglected my car a little and can take criticism.

lyleswk

Could be sensors, could be cat. Without downloading codes with VAGCOM reader, you would be guessing.

Diztek

put 100 octane fuel in your car and run it though emissions again.

jflow45

You would only need to replace the primary O2...as that one controls the mix. The secondary just monitors cat performance. Do the 100 octane thing if you just want to pass and be done with it.

StuntDiabetic

Was talking to someone today about it and they said check out the EGR valve, and check vacuum lines. I also looked at my original emissions test when I bought it 2 years ago, and the NOx was just barely under passing at 1.469 and the limit is 1.5gpm. Really need to get a OBD reader on it.

Prospeeder

1.8T does not have an EGR. It has secondary air injection but thats only for cat warm up. Nox is created from high combustion temps. So running lean can aggravate nox emissions, so check for air leaks, bad PCV valve and bad maf. Engine running too hot can have effect on nox as well. The converter also takes care of a large part of nox emissions, so if the cats getting weak that can be a sign, but you would have higher c0 and hydrocarbons from failing cat.

StuntDiabetic

Pulled a P0420 code from it, was talking to a tech about it and he said just to replace the Cat. Here's the thing, I'm leaning towards selling it and am looking for a cheap replacement so it can pass emissions, whats a good inexpensive cat? I've seen Evan Fischer for $130-$150ish online, anyone know about these?

Prospeeder

I have used cheaper aftermarket converters and they keep the light off. But none quite that cheap.