Hello,
My car does this very very occasionally. It's a '01 Veccy. Right after its automatic transmission switches to "neutral" when you press brakes long enough when standing at the traffic lights. The motor starts to wander from 900 rpm to 400 rpm, it even stopped once in the past. Sometimes it wanders for a few secs and then it raises the idle run near 2000 rpm and stays there. When I hit the gas it gets back to normal idle. This is rather annoying and I havent been able to demonstrate it to anyone because it only happens very rarely(but mostly during the wintertime). Got any ideas?
Oh, during the last winter at -25C degrees the throttle valve got jammed because it froze due some liguid goo from the small hose which connects the air intake to the "valve cap"(don't know the right term, sorry about it but anyways the hub whih covers the valves/springs etc).