Car was fine this morning. Started it up to come home, and the idle immediately went to around 2500RPM. I waited a short while during which it went back down to around 1500 for a few seconds, then it was back up to 2500. It's sort of okay to drive, but (as you'd imagine) it's a pain when in neutral, or with the clutch in. Can anyone suggest where I ought to start looking? My cheap OBD reader doesn't show any codes.
Probably of no help whatsoever, but...
Had a car which did that - but also sometimes dropped from high revs. Eventually realised that it was when it had been filled up with one of the "super" petrols. I guess the engine management couldn't cope and dropped into some fallback algorithm. Was a number of years ago so control systems were somewhat cruder than now.
Always glad of any replies. But we never bother putting any 'special' petrol in it. 'Pearls before swine' springs to mind.
Can't remember why it happened - I think there had been some supply/distribution problems and some fill-up places only had the more expensive stuff.
Well I just might have fixed it. I took the throttle off, with a view to spraying carb cleaner through it, and I noticed a rubber pipe behind it. One half goes into the manifold and the other into the head (or something like that - it's hard to see what it's for). Anyway, the head end had come off (although I'm not sure if I pulled it off taking the throttle off - it was very loose). I put it back on, put the throttle back, and at the moment it all seems good. Won't be sure till later, though.
my focus 1.6 petrol had same fault, cured by replacing split breather pipe behind manifold.
I think I know what caused it in my case. I remember that just before it decided to idle very high, it had failed to start. You know, you turn the key and it goes pfff! I waited a few seconds and tried it again, and there it was revving like crazy. I guess the pipe was so loose (no clip on it that I could find), that if the engine was going backwards for a fraction of a second during the failed start, it just got blown off. Or something.
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