BoostFrenzy

Was working fine earlier today, now when I set it the pump actuates and takes off so I let off the gas, but it slowly but surely comes down like if i set it @ 80 it'll go 79 78 77 and so forth about 1mph per 2-3 seconds, what's going on?!

Stage-3-Emre

Vac leak in the CC diaphragm? The one in my UrS4 acts funny now that it is cold out.

white90+hibredS4

do u know where the cc diaphragm is on a b4?

BoostFrenzy

yeah i need to inspect the thing, every time something gets fixed another breaks

white90+hibredS4

2nd, in that perspective people say bimmers are better, i still love audi

YucatanAudi

Definitely a vacuum leak or weak CC vacuum pump. Could be the lines (hoses), fittings, diaphram etc

AlanBDahl

I've had this same problem. When I first bought the car teh cruise did that all the time. My mechanic adjusted some sensor attached to the throttle and the cruise control started working ok.

I've had the problem return on occasion, usually when I've left the cruise switch on for a long period of time without engaging it. In that case usually powering off the cruise control and powering it back on again does the trick.

I know this isn't a solution but at least it should give you a couple of things to try.