'95 90qs: Cut Out, Hard Starts, Stall

[Doyt W. Echelberger]

I'm not talking as an expert or even an owner of such a new car, but when 
my 87 5kcstq developed the described behaviors, it was eventually diagnosed 
as a failing oxygen sensor. And all the problems vanished with a new sensor.

The oxygen sensor on my car failed progressively. Eventually, it only 
worked now and then, making for erratic performance that varied between OK 
and terrible.

The failure mode resulted in gradual creep of the mixture toward the rich 
side. When it was too rich, it would lose power and sputter and I'd panic 
and look for a place to pull off the road to get out of the way of traffic. 
Sometimes it would die at a toll booth, and I'd have to let it sit for a 
few minutes before it would restart.

Here is a test. When it sputters, FLOOR IT. Flooring it opens up the 
throttle and allows large amounts of air to enter, which temporarily 
provides air to the rich mixture setting, and the power returns for a 
little bit.....3-4 seconds, or as long as the throttle is wide open.

If flooring it helps, you are probably dealing with a rich mixture, and 
that might be due to a failing oxygen sensor. Then you can go to the 
expense of having a mechanic use a special instrument to test the cycling 
frequency of your oxygen sensor. Or if your sensor is over 30k miles old, 
you can just replace it.

Doyt Echelberger


 >>>>>>>>>>>>>>>>>>>>>>>>>>>
At 12:04 PM 8/27/2000 -0400, you wrote:
>Hello,
>My 1995 Audi 90q (73k miles) has a real problem. It started
>as the occasional stall at idle, then progressed to quick,
>intermittent cut out while driving. Now, at road speeds, the
>engine will sputter rapidly and die altogether, and be
>nearly impossible to restart. Car backfires slightly. After
>letting it cool a bit, I can restart and sometimes run for
>1/2 hour or more with no problems.
>At first, I thought that i had gotten a bad tank of gas. Ran
>some methanol through, with limited, short-term success. may
>not have helped at all, in retrospect. I am two tanks of gas
>past that first suspect tank. I have run injector cleaner
>through before and after this started. All panel indicators
>are normal.
>Any ideas?
>
>-DanZ
>
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