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Approx 6 months ago, I purchased a Saab 9000 turbo '91.

Recently it has developed an over revving problem?

When the car is at a standstill it revs at approx 2000 rpm.

It doesn't seem to happen when the engine is cold, but once the engine has been running for a time the engine revs at approx 2000 rpm, the engine tries to cut to its normal 1000 rpm but revs back to 2000 rpm.

Can anyone suggest anything ?
 

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this is normaly the iac valve sticking, take the iac valve off including the pipes clean it in a tub of parafine making sure you get all the gunge out of it, try not to use carb cleaner as this can rot any plasric/elect connections, it might take some tome to get all the gunge out so take your time.
 

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I've had this problem with my 9000 LPT and it turned out to be much simpler. It was one of the engine breather pipes that had come loose allowing air into the inlet manifold, by passing the throttle butterfly. It was a little metal pipe about 6mm diameter which had come loose. I just squeezed it slightly with a pair of pliers to make it an interference fit again.

I found it due to the hissing noise fron behind the rocker cover at tickover.

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I would agree with Paul, check the rubber grommits where the elbows and vacuum pipes go into the manifold - assuming you have the grommits. Mine has gone a couple of times, causing the engine to do exactly as you describe. If not, check all vacuum lines.
 
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