Why oh why does my Focus occasionally rev hunt, 500 to 900 or a 1000 rpm when warming up or warmed up, especially when coming to a stop at traffic lights. Ive tryed so many things it might be on the net, Pcv valve and hose, Icv, air leak, plugs,leads, all new!, but it still idle hunts 9 times out of 10 when stopped.When coming to a stop the revs raise to about 900 then settle to 700 rpms which is normal when clutch is pressed and released. But when stopped the revs will hunt 500 to maybe 1000 rpm's on there own up and down. Any ideas anyone! Ive been told when it has had a new cambelt fitted sometimes you may need the car pcm updated which may cure problem is that true.? Car runs fine otherwise no missing or hesitation.

Try checking the Throttle Position Sensor.

Ive actually swapped my father in-laws Throttle Position sensor over with mine just to see and made no difference, at all. Stupid car!

take of the throttle body n give it a good cleaning, there should be a little breather hole in side this does get badly clogged up hence what your experiencing.....

take of the throttle body n give it a good cleaning, there should be a little breather hole in side this does get badly clogged up hence what your experiencing.....

carb cleaner of its valuant