'86 944 turbo

Must be the guru chips because I failed the NOX. My HC was 23 and the limit was 112. The CO was .09 and the limit was .63 What do you guys get on the NOX test with aftermarket chips. On the second test I had the car on 3rd gear (1726 RPM) and put a fan in front of the car and passed.

Matt H

Is your car equipped with a catalytic converter?
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'86 944 turbo

Yes, my car is equipped with a catalytic converter.

Matt H

You dont say how high the NOX was. Generally, I would look at the cat first since everything else passed. With the rest of the readings being so low that could be the simple solution.
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'86 944 turbo

the NOX was 1919 and the limit is 1252

RajDatta

I had a similar problem and swapping the O2 sensor fixed my problem.
Raj

Matt H

02 sensor is also a good guess. I will grab a list of the things it could be for you tomorrow.
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Flight_951

The high NOx had been plaguing my car for over two years. This is while I had stock, then Autothority, and now Guru chips. I wasn't sure why. Finally a couple weeks ago, my car failed the test miserably (high HC, CO, NOx) at both rpms tested. I now believe the high NOx had been a symptom of a failing and clogging cat (creating high combustion chamber temperatures) for some time, and it finally let go altogether.

On the bright side, I just received my new 3" test pipe with cat from SFR yesterday. I'm installing it Tuesday and will retest the car. To be on the safe side, I changed the oil and will install new plugs too, but I'm definitely expecting to pass.