1990 Audi 100 stumbling, hesitation

[Dennis Larson]

I have a 1990 Audi 100 with about 190,000 miles on it that has had
deteriorating acceleration for several months. The car is used by my
wife for short trips, I use a 1985 Audi for myself. Last winter I
drove the car around for a day and the original power and zip came
back.

After driving it again after 6 weeks the car had gone downhill again,
worse than ever, so I added Techron and my more aggressive driving
habits for a day or two. It didn't help this time.

On startup the car is barely drivable and a long warm-up helps. It
acts like it is in a very lean condition with some mild backfiring in
the intake. So far I am investigating vacuum leaks. Pulling the dip-
stick out or removing the oil cap will stall the car out.

It idles perfectly, but accelerating and accelerating when in neutral
produces some mild missing. Flat and level driving is perfect.

I do have a vacuum problem with the climate control, the AC will
cycle from the dashboard vents to the bi-level position on
acceleration and the door locks are not functioning properly. But I
have not found any vacuum leaks yet for these problems.

Today I checked out the ignition wires and replaced one with higher
ohms 11k, but that did not improve the situation. I have some sensors
to check out, possibly a fuel filter (I am the third owner). I have
the full 3 volume repair manual on hand and am acquainted with
checking various sensors and their ohm values but some direction
would certainly help.

Dennis