Could it be the O2 Sensor?

[Dan Cordon]

> Another test is to find a nice flat stretch of road and set the cruise
> control. You should feel a nice steady ride. If you feel "surging" then
> the O2 sensor is shot. Surging is where you feel the engine accelerate,
> then let off, over and over. On a flat stretch, the cruise should be
> able to hold the engine pretty steady, with no surging.
>

Wow....that's a stretch. Not that the test is bad, but how many of the
older audis still have the cruise control working :o) ??  Seems like
cruise control questions pop up on the list as much as window
regulators.

If you can pull the sensor from the car, you can also use a propane
torch to watch for response on a volt meter. Not only is the voltage
itself important, but the response time seen when taking the flame on
and off the sensor. If you do a "Google" search you'll probably find a
ton of tests for O2 sensors.

--
Dan Cordon
Mechanical Engineer - Engine Research Facility
University of Idaho