Three problems related to cruise control have been reported for the 1999 Audi A4. The most recently reported issues are listed below.
Throttle sticks at low ambient temperature. This has occured several times in the last month when temperature was below 10 f. It occurs with the cruise control on and when the cruise control is off. Very dangerous situation and hard to stop vehicle with a throttle stuck open. Letting the car sit for a few minutes warms up the throttle body enough the the throttle unsticks.
While traveling on the highway on a sub zero (-6 degree f) night, my car which was set at 55 mph on cruise control, accelerated on its own to 62 mph, and the throttle became stuck. Braking, and pushing the appropriate buttons would not disengage the cruise control. I had to physically push the foot brake as hard as possible to force the car to a stop, and then the car was still accelerating on its own when I released the brake. After starting the car and turning it off 3 times, I finally disengaged the cruise control and made it to my destination. On the way home, without touching any cruise control features, the throttle once again became stuck and was trying to accelerate the car. Today I had the car serviced, and I was informed that they had received 3 calls during the time period I was there regarding a similar situation with vehicles that contain the same or a similar engine.
The cruise control became stuck, while driving.