90 100q stalls out

[Ben Swann]

My main suspicions to check in this order:

1.	Air Leaks – vacuum leaks, torn intake hose, leaking valve cover gasket, etc.
2.	Oxygen sensor going bad and sending incorrect signal
3.	Faulty DPR or temp sender
4.	Failing fuel pump or relay – can jumper 30 to 85 with wire to bypass or use
orange relay for fuel pump always on with ignition.  If pump is cutting out, you will
experience the symptoms described.
5.	Bad gas.
6.	Ignition miss – I presume you have already checked cap, rotor and plugs in
decent shape, but wires can and do get flaky.  Following that coil, distributor/hall.
7.	Fuel Distributor.

Ben

[Date: Wed, 26 Dec 2007 17:21:14 +0000 (GMT)
From: syljay at optonline.net
Subject: 90 100q stalls out
To: quattro at audifans.com
Message-ID: <e7d997966042.47728d8a at optonline.net>
Content-Type: text/plain; charset=iso-8859-1

My 1990 100q, manual, non turbo stalled out at the mall.Pre-existing condition:Car has
an exhaust leak. I'm pretty sure its at the downpipe/cat flange. The leak noise goes
away after the car warms up. Last time I was under the car, about 6 months ago, I left
the flange bolts/nuts a bit on the loose side cause the downpipe flange was rusty, thin,
and bending. I suspect with a bit of bouncing of the exhaust system, the flange worked
its way a little loose. When the exhaust pipes are cold and contracted, an opening
appears. After a warm-up, the pipes heat up, expand and seal off the gap.I've had this
exhaust problem for about a month now . .. with no stalling issues.Sequence of
events:Went to the mall on Christmas Eve in the 90 100q.Drove to the first store with no
problems.Came back after about 45 minutes and drove car to next store about 1 mile away.
No problems.Came out of the store about 30 minutes later - started the car - and
proceeded to drive out of parking lot.I felt something
 wrong, the engine would buck/miss if given too much gas. I looked for an empty parking
spot and creeped towards it. Engine was missing badly and finally stalled out. Engine
would not start, cranking was fine. We got some good samaritans to help push the car
into the parking space.I called wife who? picked me up in the 88 5kq.Two hours later, I
went back to get some things forgotten in the 90 100Q.I swapped out the Fuel pump relay
with the one from my 88 5kq. Car started right up. I put back the original relay, car
started right up.I went home, got a spare fuel pump relay, and drove back to the car
with wife in tow.Put in the spare relay, started the car - no problem.Let the car warm
up, and drove around the parking lot a bit.I felt a hesitation a couple of times when
starting off and giving gas. I let it warm up some more and tried again. I was easy on
the gas and the car seemed to work ok.I decided to try getting the car home.All worked
ok, until I got to a stop light just before
 the entrance to RT 80. As I? was starting off, the car bucked and I thought it stalled
out. Being in traffic, I didn't watch the RPM gauge and tried starting the engine . .
got a grinding noise . .the engine was not stalled.I drove off, being gentle on the gas.
By now I was suspecting that giving too much gas too quickly resulted in the
bucking/cutting out. Maybe the engine torque and engine rotation was moving something.I
drove all the way home (about 10 miles) on the highway with no problems? - - being
gentle with the gas.And now, for the $64,000 question - Whats the problem?SJ in NJ]