I have a 1998 A4 2.4 with about 114,000 on the clock. Recently I have found that the engine cuts out when I have the aircon going at full blast when I stop at lights or have to allow the engine to run down to tick over. Also the same thing occurs when I am manoeuvring on full lock steering - the engine just stops. I have spoke to my mech who rather vaguely said the manifold "need a blow out". He has had the opportunity to do this but no result. Any ideas ?
Watch the rev counter and note the engine speed with no air-con on and then again when air-con is kicking in and when you hold the steering wheel on full lock. Both of these will put a fair load on the engine and if it is idling at too low a speed, it will cut out.
I'm guessing there is an idle valve/throttle body fault...