I have an 09 Ford C-Max; 1.8 petrol vehicle which has a problem with the idling speed when re-starting the car after it has been parked for an hour or so. When starting from cold in the mornings, the engine rpm is about 1100rpm and normal idle speed seems to be about 750rpm. However, if the car is used for a while and then parked for between 1 and 3 hours, on restarting the car the idle revs drop down to 500rpm at which the car is struggling. At this problem speed, dabbing the accelerator pedal has no effect, the revs refuse to increase and only depressing the accelerator pedal hard down will force the revs up. On occasion the engine will just cut out at the low revs. Sometimes the speed will oscillate between 750rpm and 500rpm. The dealership where I purchased the car have no idea how to cure this, they have cleaned the accelerator sensor but this had no effect. I would appreciate some advice as to what could be causing this problem.