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99 olds alero idling too fast....

i have a 99 alero that occasionally idles at 2400 to 2600 rpm's after driving on the highway for a while. it may run fine for 2 or 3 days, but then i notice the accellerator a little 'spongy' on the highway. then i know the idle is running fast. it does not correct itself in the city, which makes for some interesting driving. the next day it will fast idle for a second, but then correct itself. so something appears to be heating up and malfunctioning..
reading different websites, i replaced the MAF sensor, then discovered a vacuum leak at the PCV line. neither cured the problem. i've also read about the idle air control valve and idle speed control motor. are these my next guesses? the MAF sensor was used, if that helps.
please advise what you think would cause this. it seems the hotter it is (with A/C on), the more often it happens. but the A/C doesn't have to be on for it to happen.
help? my brakes can't take much more of this!

Optional Information:
1999 Oldsmobile alero v6

Already Tried:
vac leak, MAF sensor,

Customer (name blocked for privacy)

Status: Closed Value: $8

Remove the iac(idel air control valve)and clean it with carb and choke cleaner,also clean the bore that the iac sits in,clean it good,and reinstall the sensor and see if that helps,get back with me after you do this

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Reply to GENE's Post: is gumout the same thing as carb and choke cleaner? i'm a little hesitant to spray everything the way we used to, when carburaters were king. please advise if the engine should be running, and advise where the idle air control valve is.... i've been unable to get a good photo of this item, like i did with the MAF. can this be cleaned too, or are you confident of the idle air contol is the problem? do these heat up and malfunction?

Yes use gumout spray cleaner,do this with the car not running.The iac is in the throttle body,two screws hold it in,ask the Parts store to show you one.it's not hard to find it also has a connecter for the wiring harness,look beside the egr valve on the throttle body.You can use the gumout on the maf also which is always a good idea,just spray it and let it dry as this stuff dries really fast'also is the service engine soon light on?

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Reply to GENE's Post: service engine light doesn't come on consistantly when the fast idle happens. i had it at an auto shop, but he couldn't pinpoint what the problem was, since the car wasn't acting up at the time. but he mentioned several of these possabilities. the previous codes didn't show the problem. is the idle air control valve near the MAF? i've seen pictures of the control valve, and should be able to identify it for what you described, near the throttle body. 2 screws and wiring connector. got it... anything else? i could spray the inside of the MAF also, you said?

Yes just spray the maf on the inside,just follow the tube that the maf is in to the throttle body, where the clamp is is where the iac is within a inch of there i belive that the connecter has 4 pins in it and is flat

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Reply to GENE's Post: last time and i'll accept.
1... the gumout won't leave a residue?

2,,, i just went out and lookd; there are two items near where you described... one is about the size of a bottle cap and shallow. the other is slightly bigger in diameter and about an inch deep. which is the iac? i don't know where the egr is, so i may take the wrong thing appart.

3... will a gasket get distroyed in this process? do i need a new one?

4... i've checked aroumd.... the iac valve is under $50; just replace it, because of the 'heating up' condition? i don't want to eliminate this, if cleaning doesn't help. thanks again, and i'll accept whatever your final recommendation is.

The best way to do this is replace the iac,just remenber to clean the hole that the iac sits in,the cleaner does not leave residue.the iac is the biggest sensor in the throttle body and it has a o-ring around it.if you replace the iac follow the directions that come with it.or if you need any help i'm on this website from 6pm to 11pm every night.This is probably the problem also make sure you dont have any vacuum leaks

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