98 grand prix gtp high idle

bkautoman

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98 grand prix super charged 3.8 Any suggestions? I assume vacum leak, Are there any common places to look for vacume leaks. when starting cold car idles arround 1800 as it warms up goes to around 2800. will not caome down at all. IAC is at 0 which would indicate a vacum leak. I was unable to pinpoint a vacume leak so went ahead and removed intake. cannot find any obvious signs of leak. Any suggestions Thanks
 

kev2

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??? supercharged engines have + manifold pressure,

So lets start with simple things
Is service engine light on?
Does the SEL perform check when starting vehicle?
List ALL modifications, aftermarket parts, add ons etc.
 

Gus

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You should have sprayed carb cleaner around the engine BEFORE taking anything apart....when I had a high idle and vac leak on SC'ers, it was usually the gasket between the upper plenum and the lower intake....it would crack.....
 

bkautoman

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No check engine light on, SEL checks. Done the carb cleaner check. As far as mods, cold air intake thats all I know of. bought the car wrecked it ran fine after fixing it ran fine and thn one day went to start it and idle slowly started increasing as it got warmer. in the prosses of putting intake back on will know if that helped in a couple of hrs. cold not find any bad spots in gasket unless it was in a spot that ripped when taking off.
 

ron350

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Have you cleaned the IAC (idle air control) valve and passage yet?
When you say remove the intake are you talking about the air filter and tubing? I am old and an intake used to mean “Intake Manifold” so I get confused.
If you are talking about the air filter and boot that goes on the end of the throttle body, that should not change RPM.

That L67 has several rubbers vacuum lines that are known to crack and cause high idle.
 

bkautoman

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Problem fixed. Replaced intake gaskets and idle's fine now fixed fixed fixed
 
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