I need to know the relationship/connection between the throttle position switch, the Idling Control Valve (ICV) and the AFM for my E34 520i Auto M20 engine.

I seem to be continuously having idling problems. Have checked and changed the bellow and other rubber hoses, and NO vacuum leaks. Someone at the workshop seem to have meddled with the adjusting screw at the throttle body to increase the rpm to avoid the bad idling. But the idling is very bad until it stalls when D or R is engaged.

I think I'll be able to solve the problem if I know the relationship between the TPS, ICV n AFM.

Your kind advice needed urgently.

BTW, car runs beautifully ... with new thermostat 70 Celcius with the temp needle at exactly 1/4. Wonder whether it's too low. But by our standards here in this very hot tropical climate, it's fine at 1/4.

H Mayer
Malaysia