Usually, the engine is either idling or just above idle, when something happens and the idle speed drops to about 500 rpm. Sometimes the engine tries to compensate and then starts to idle at 1500 rpm, other times, it just stalls.
Afterwards, the engine cranks and I can get it to start but then as soon as I let go of the key, the engine is only idling at around 500 rpm and it just stalls again. I've noticed that it tends to do this more often when the engine is partially warmed up, but not fully at its normal operating temperature.
Anyone have any ideas what it could be? Any help would be greatly appreciated.