One problem related to engine has been reported for the 1998 Audi A4. The most recently reported issues are listed below.
In very cold weather, the engine sticks and holds a speed of 6,000 rpm. This condition lasts for at least 40 minutes during which time the car is not controllable. I have had this happen four times. I have involved the local Audi dealer as well as Audi of America. They have attempted to fix this problem four times without success. Audi of America is refusing to either acknowledge or take responsibility for this problem. The first time this happened was on Jan 16, 2003. The last time it has happened was Jan 16, 2004.