I have a 99 focus 1.8 petrol and its driving me nuts.
It has developed a high idle at normal driving temperature, it used to idle aroung 800rpm but is now up to 1000 rpm. The revs also surge when i stop at lights/traffic etc.
For example if i am going 40 mph and stop at lights dip the clutch or flick into neutral the revs will rise to about 2000 rpm and after a few seconds settle down at 1000 rpm.
I have put a new iac valve and speed sensor in the car but the car still surges.
I have had a vacuum hose replaced recently by a mechanic who said that the old one had collapsed, when he was installing it he pulled away and took it to the boss of the garage and seemed to show him something, is there a chance that the hose was the wrong type?
I have also been told that it could be something to do with the pcv hose/valve.
99 1.8 engine surge/high revs at idle -
It sounds a lot like the throttle position sensor. I had the same problem with mine.
It shouldn't be too difficult to get a garage to replace it for you. Alternatively it's not a difficult job to do yourself. Its at the top of the engine bay (follow the throttle cable) and is held on with two hex screws.