hi everybody. can anyone tell me whats making my cars idle speed increase and decrease while i am waiting at a junction or lights. its a 1998 1.8gdi.then after about 4 to 5 minuites idle increases to 2500/3000 rpm. aahhh please please help.
thanks marc.

Try cleaning the throttle housing on a gdi, if it is still the same after then possibly a major repair required.

Also sounds like you need a clutch from your other post, would try fixing the idle fault first as it may cause the car to fail emissions at mot time. Car may need a engine strip (decoke) to fix!

If a decoke turns out to be required (expensive) and you need a clutch, car not worth fixing. Sorry bud but if was my car I would sell it on.

Sound like you have some vacuum leak somewhere.
It could be something minor, like a broken/leaking vacuum hose on the heater controls, or something more serious like a keaking head gasket.