over revving

[oddball]

Hi people, any help on this topic would be very much appreciated.

I have a 1999 1.25 zetec fiesta which has decided to start over revving at start up and once warmed up it will not settle below 1100/1200 rpm. at start up it flies up to around 2000rpm and stays there for a while or until i move the car.

I have had it into a garage who put it through a diagnostic which returned no faults(twice) and still i have no idea what is causing it to run like this.

If anyone has any ideas as to the cause or anyway of how to remidy it i would be very thankful.

[mintalkin]

it could be you idle speed controlle valve playing up, these can be removed and cleaned with carb cleaner.it could also be air getting into the intake system

[maxrox85]

My 1995 ghia used to do this also, she started at 2000rpm and came down to about 1200rpm after about a minute... I think it is the idle valve myself. Mine now does this to a lesser degree because she also seemed to have "kangaroo petrol" and the rev's randomly went up and down so i had the air bypass valve replaced... that knocked the bunny revs on the head and it calmed the start up revs for a year or so but now it does seem to idle high again so will look at replacing this too :)