engine idling over accelerated

Saturn 1997, 1.9L, SOHC, SL1; with 206,000Km, standard transmission. Location: Toronto, Canada. engine idles to 2000rpm when turning on cold, but settles down to 900
warm. now NEW problem: when driving, every time I switch gear in tranny, engine runs (away) up to 2000rpm , and comes down veeeeeery slowly (when stopped at a traffic light, for instance), or between 2nd and 3rd This makes difficult the synchronizing gear change, as I have to wait until rpm comes down; I'm afraid of damaging the clutch. Please help. TIA. daniel rozenberg.
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This is a very common problem with cars of similar age. It is caused by a slow acting (dirty) IAC Idle Air Controller which is a small electrically actuated valve controlled by the computer and located on the rear side of the throttle body.
I suggest you purchase a new throttle body gasket and a spray can of intake manifold cleaner. Remove the throttle body, then remove the IAC from the TB. Carefully clean the IAC and the TB paying particular attention not to damage the IAC and to fully clean the air passages and IAC seat in the TB. Spray a liberal amount on intake cleaner onto the insides of the manifold. Reassemble and install the TB on the intake manifold then restart and spray cleaner into the running engine. I suspect there are several videos (of varying quality) on YouTube and that the counterman at the auto parts store will be helpful when you purchase the gasket and manifold cleaner.
Good Luck, YMMV
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Not sure if this applies to this particular IAC motor but generally DO NOT try to energize it while removed from throttle body.
The ones I've seen are a stepping motor that moves the valve plunger in and out. When the engine is first turned to the run position, the plunger is extended until it hits the stop. It is then backed off appropriately as engine is cranked. I've had a few that if you have it out of the throttle body and energize it, will not retract and will then not fit back into the throttle body without breaking the IAC motor. Sometimes even the new ones from the store won't fit. My buddy has a snap-on device that when connected to the IAC motor (basically a 4 lead step motor drive) will retract the plunger so it will fit into the throttle body.
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