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MGF engine over revving when hot and stopped in traffic.

I have an MGF. The engine starts OK and runs smooth at speed but when I come to a stop at the lights or enter a garage the revs go up and down between 900 and 1200rpm. Can still get the gears with no grating.

Some times can 'clear it' or reduce to say 500rpm by over revving the car throttle pedal. Garage have cleaned out the step motor but to no avail.

Asked on 16 October 2012 by Racing Green

Answered by Alan Ross
Make sure the fuel filter is clean.
If okay then check air intake/vacuum system for leaks.
Then check the throttle valve to see if its sticking/also the linkage.
If okay then check the IAC (idle air control) valve, idle speed control actuator.
Lastly check the ECT (engine coolant temp)sensor.

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