I have a 2004 Ford Focus (automatic). It has been revving really high when starting up cold (after sitting overnight for example). It revs up to 2500-3000 rpm for about 60 seconds (sometimes longer) before coming down to 1000 or just under. Sometimes when driving it will start to accelerate slightly on its own before it stops, or RPM will jump up quickly when driving at a constant speed with constant pressure (like 50kph). As a result (I would assume) I am getting horrible gas mileage (takes about 40L to fill and I'm getting about 350km per tank).
Had fuel filter replaced, idle air motor replaced, mechanic checked for vacuum leak (there was none) and inspection could not reveal any cracks or other issues. No check engine light is on at all.
Any assistance on what I should have done or get checked out?
Tuesday, April 30th, 2013 AT 9:59 AM