A week or so back I posted that I had a problem with a ford focus Mk1,
1.6 petrol, 2001 where the idle would sit at 800rpm and then every two seconds would blip to 900 or 1000 rpm. I reported that a can of throttle body cleaner had cured it. Car has done around 140,000 miles.Alas a few days later it started blipping again so I decided this time to remove the idle control valve to thoroughly clean it, again with throttle body cleaner.
I now have a worse problem. When putting the car in neutral the revs will stay at 2000rpm before falling back to around 900 rpm after around
2 seconds. Also on start up the rev will jump to 2000 rpm before falling back to a more normal idle speed a few seconds later. Revving the engine and then releasing the throttle results in the revs dropping to 2000 rpm before falling to 900 rpm after 2 seconds.I notice no drop off in performance when driving.
Any suggestions?
Things already checked: No apparent air leaks. Hose behind manifold that often fails was replaced less than a year ago. Gasket on throttle valve looks ok and I have carefully re-seated the valve a couple of times. Disconnected the throttle valve electrical cable - car still starts at
2000rpm and after 2 seconds falls back to 'near' normal idle revs. I'm assuming that the default position of the valve is closed as springs shut with no electrical connection. Replaced the throttle position sensor (just in case). The throttle is not sticking and the throttle butterfly fully closes immediately when the throttle is released.