Oxygen sensor?

[mmlai!jensen@uunet.UU.NET (Jim Jensen)]

I am wondering if anyone has had any similar experience or advice.  I
have a 1990 80 Quattro, and was driving from Hudson, NY to Baltimore,
MD on sunday afternoon/evening through a lot of slush and snow.  about
18 miles from Delaware bridge on 295 in NJ when the engine stopped.
(this was after about 5 hours of mostly continous driving, only
stopped for gas and french fries) There was nothing unusual about when
it stopped - no noises, I didn't downshift or accelerate.  it just
slowly died. (full power to nothing in about 15 seconds).  I pulled
off and had the car flat-bedded to Cherry Hill Audi dealership, where
they looked at it on Monday morning, said there were no faults stored
in the computer, and couldn't figure anything out.  they checked the
CO output, etc. and determined that the O2 sensor was giving bad
information to the engine computer.  thus, the computer would lean the
engine to the point of it not running.  They decided that the O2
sensor was bad, since disconnecting it would allow the engine to run
normally.  So they disconnected it, and I drove home to baltimore
monday afternoon (they didn't have one in stock to put into the car).
gas milage went up to about 27 mpg, compared to about 21 mpg on friday
night (similar speeds, etc).  So I took the car to Audi dealership in
Laurel, MD, where I normally have it serviced, and they tried to
re-create the problem by reconnecting the O2 sensor.  They drove it 31
miles, and it runs fine.  according to them, the O2 sensor is working
as it should.  They said they would replace the sensor if I wanted,
but they would prefer to recreate the problem themselves before
replacing it.  (they quoted $170 for the part, and $50 labor to
install).  they also said it might be the engine computer.  

I would be interested in any information/advise, etc from anyone who
might have some.  On the good side, Audi Advantage paid for the
flatbed from the highway to the dealership - about 30 miles.

	Thanks,
   Jim Jensen                        
   Martin Marietta Laboratories      jensen@mml.mmc.com
   1450 South Rolling Road           jensen@sun.soe.clarkson.edu
   Baltimore, MD 21227-3898	     jensen%mmlai@uunet.uu.net 
	(410) 204-2605