my wife's focus 1.6 zetec 2006 petrol car, the revs keep jumping to sometimes over 2k, then sharply drop down to almost stalling, and some times it does actually stall. reading other forums i thought it might be the idle sensor, but when your driving at a constant speed, you can feel the car juddering, would that sensor do that too??? if it is that, do i need a new sensor, or would it other one just need removing and cleaning? Cheers in advance for any advice tom