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RE: quattro-digest V1 #672
Hi Paul,
Don't know a lot about the 90q, but you should be able to diagnose a clogged
cat with an exhaust back pressure test run at 2000+ RPM.
Bentley gives inspection criteria for cats like visually inspecting the
catalyst material to see if it's "clean" and intact, and banging and shaking
it to see if it's rattling, but they can only be done after wrestling with
the nuts and bolts to get it off the car. I would be hard pressed to
believe that you have either a bad OxS or excessive carbon deposits, unless,
of course, you are totally unaware of the running and operation of your
vehicle. To the contrary, I would believe that you'd be more aware of how
the engine is operating when going to an emissions test.
Your NOx results are higher than any I've seen on the list for any vehicle.
Is it possible that the test results were incorrect for some reason?
For example here's a post by Mike Murphy on his NY emissions test and Mike's
car might have been expected to test higher than normal for NOx:
NYS specs and results
HC CO NOx
Test limit 2.00 30.00 7.50
Test result 1.43 11.30 6.64
Not a lot of beef in here but HTH.
Cheers!
Jim Jordan
81 5KT > 300K Miles
> ------------------------------
>
> Date: Fri, 26 Nov 1999 19:23:58 -0500
> From: PN <pajono@ctconnect.com>
> Subject: 90q fails emissions
>
> I took the new 90q through CT emissions today and failed
> miserably for high
> Nitrous Oxides (3726 ppm, max allowed is 1121 ppm).
>
> Possible causes listed for the NO failure are bad O2 sensor, bad cat and
> high compression caused by excessive carbon deposits. Do these sound
> reasonable? It's possible I have a clogged cat, and that might
> explain why
> the car also doesn't like to rev. Is it possible to see the honeycomb in
> the 90q cats, or does the tubing into and out of the cat bend?
>
> Thanks for any input, and any BTDT experiences,
> Paul
> 90 90q 20v
> 86 944
>
>
> ------------------------------