poor running 88 5ktqa - more info

[Ameer Antar]

I'd strongly suspect a vac. leak somewhere. I had a similar issue before where the car would run ok fro a few miles and then totally crap out the next. It turned out to be a hose had fallen apart right next to the hose clamp so it was hard to see. Every bum the car felt changed the position and sealing of the hose, so the car would go from bad to worse and back. Although it might be possible, esp. if several sensors going bad, I doubt sensors would cause a severe running issue as your stating. O2 sensors and temp sensors only have a limited affect on the fuel delivery. The main deciding factor is the air-flow plate and the rest is just adjustments. If there's any sort of vac. leak, the plate will not go high enough to deliver the right amount of fuel.

In any case, it's a really good idea to test sensors when your troubleshooting so you can eliminate possible problems, but I'd start to look carefully at all your intake hoses. Carefully remove each one b/c cracks/tears usually don't stare at you in the face... they usually hide on the bottom or near a hose clamp. Who knows, the problem could be an ECU malfunction, but you need to be sure you can eliminate certain possibilites. good luck.

-Ameer

----Original Message----
Date: Wed, 31 Mar 2004 11:06:29 -0600
From: "Livolsi, Stephane" <Stephane.Livolsi at investorsgroup.com>
Subject: poor running 88 5ktqa - more info
To: "Audi Quattro List" <quattro at audifans.com>
Message-ID: <A9CCC2FEA3353D4B9BB3D1DC8939777004CC176B at igamail3.iga.bz>
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I copied my original post for reference.
Last night I unplugged the o2 sensor and drove it.  Same problem -
cutting out/missing under acceleration - actually felt worse which is
probably good, right? meaning the o2 sensor is working?
 
Now this morning was interesting.....
Slightly colder this morning (about 0C) and the car started fine without
giving it any throttle, but when I did give it throttle it sounded like
an air colled VW and there was some (gulp) bluish smoke which cleared up
(valves?)  Anyway, heading down the road the throttle felt more
responsive than yesterday and lo and behold I could accelerate very
nicely with heavy throttle application.  This lasted for about 2 minutes
and then the cutting out/missing returned.
 
So, what changes in the first couple of minutes of engine operation?  O2
sensor is in open loop until it warms up but it has the heater wire so
it should only be a few seconds before it goes to closed loop, right?
What else is there?
 
I am strongly suspecting that temp sensor referred to in the other posts
for the 89 90Q.  Is it the a single wire sensor at the upper rad hose on
the engine, above the 4 wire MFTS?
 
Stephane