[200q20v] Too many error codes-where to start?

Forhan, Thomas Thomas.Forhan at mail.house.gov
Wed Nov 15 10:30:18 EST 2000

Ran the engine diagnostics sequence this morning, which produced the
following codes:
2121 - idle switch
4431 - idle stabilization valve
2342 - O2 sensor
4442 - waste gate frequency valve

I also see that if you have the VAG tool you get more than just the blink
codes, because the Bentley notes further diagnostics is available in the VAG
display "in [addition] to the component". Of cousre, I have no access to

Here is the background:

Bought the car with 125K miles  last year from a dealer, clearly
(whooee!)some previous owner chipped it.  The car is much, much faster than
my old 90 200 TQ IA Stage I, and a friend with an S4 commented that it is
much, much faster than his stock S4. But no markings on the outside of the
ECU though bag cut and retaped nicely. Maximum boost indicated on factory
gauge is 2.4 bar, for what it is worth. 

The problem is that the car occassionally stalls coming to a stop and always
misses during low rpm acceleration, once rpms are up about 3000 rpm it feels

First diagnosis run about two months ago: I got a 4431 and replaced the idle
stabilization valve, and cleaned all relevant contacts. No change.

Just about then the turbo boost valve thread started here, and the symptoms
discussed seemed exactly like my problem. I replaced the TBV and hose and
the problem went away for about two weeks, and then returned. I replaced
with another new TBV, and there was no change.

So I ran the diagnostics again, and there are so many errors I don't know
where to start. Is there a common thread above? 

Unfortunately,  I am a parts replacer, not a mechanic. Between this and the
no heat (which I am working on, thanks) my wife is getting very skeptical of
this purchase for a "family car"


Tom F.
1991 200Q20V Avant

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