Why does your golf MK2 1.8 8v idle goes up and down why it gets warm you put in a new idle contol valve and its still doing it?

ISVs are normally very reliable units and not usually the cause of erratic idling.

Vacuum leaks are a frequent cause of idle troubles. Trace the vacuum lines that run from the throttle body and check all connecting pieces are in good order as well as the vac pipes themselves. Also check the short rubber connector between the camshaft cover and the plastic 'drum' above it - leaks here will prevent the engine from idling correctly.

Check the connection to the throttle position switches on the throttle body. The lower switch senses the 'throttle closed' position and engages the ISV.

If there are any doubts about the fuel mixture then get the car tested/adjusted for emissions.

Disconnect the ISV when the car is hot and see if there is any difference to the idle speed. Ideally there should be little or no difference if the idle speed screw on the throttle body has been correctly set for 950 rpm. If there is a large difference (and everything else has been checked) then leave the ISV disconnected and turn the idle screw until the rev counter is as near to 950 rpm as possible. Finally reconnect the ISV.

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