car idles @ 3500 rpm at start and 1900 rpm in drive? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 01-20-2008, 12:55 PM   #1
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Default car idles @ 3500 rpm at start and 1900 rpm in drive?

when i first start my car it idles at roughly 3500 rpms and after 7-10 minutes it goes to 3000 rpms and stays about riggt there untill i put in in drive then it drops to about 1800 rpms to 2100 rpms and stays about in between there..

is this my iac causing this.? or what else could it be..
i dont recall ever changing the iac on the 88 bonn.. thanks guys
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Old 01-20-2008, 01:14 PM   #2
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My first thought was the IAC. Have you at least cleaned it recently? Could be carbon deposits keeping it from functioning properly.

Cleaning instructions: http://www.lesabret.com/phpBB/viewtopic.php?t=4054

Another thought that comes to mind is a faulty TPS, but I would think that it would throw a code by now.

Speaking of codes, are you getting any?
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Old 01-20-2008, 01:18 PM   #3
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Quote:
Originally Posted by Alibi
My first thought was the IAC. Have you at least cleaned it recently? Could be carbon deposits keeping it from functioning properly.

Cleaning instructions: http://www.lesabret.com/phpBB/viewtopic.php?t=4054

Another thought that comes to mind is a faulty TPS, but I would think that it would throw a code by now.

Speaking of codes, are you getting any?
no codes besides 39-tcc and thats about it...i will try and clean the iac. but how and what do i use to clean it.? thanks
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Old 01-20-2008, 01:25 PM   #4
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Quote:
Originally Posted by 88bonnsse
Quote:
Originally Posted by Alibi
My first thought was the IAC. Have you at least cleaned it recently? Could be carbon deposits keeping it from functioning properly.

Cleaning instructions: http://www.lesabret.com/phpBB/viewtopic.php?t=4054

Another thought that comes to mind is a faulty TPS, but I would think that it would throw a code by now.

Speaking of codes, are you getting any?
no codes besides 39-tcc and thats about it...i will try and clean the iac. but how and what do i use to clean it.? thanks
I used brake parts cleaner for mine. Then I took steel wool and just kind of polished off the deep carbon build up. I really wouldn't have benefited much if I hadn't taken off the TB and cleaned off the area that it was mounted on to. It was CRUSTED in crap.

Not sure if TB/IAC setup is similar or not.

It did quiet it down a lot though, surprisingly.
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Old 01-20-2008, 01:57 PM   #5
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throttle body and maf are 6 months old and should be fine but ill clean it anyway.. and then i will run some sea foam thru my vacuum line and see what happens
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Old 01-20-2008, 01:59 PM   #6
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Seafoam FTW. Though it makes me feel like it'* not doing anything on this car when it doesn't make a hellacious cloud of smoke :(. But it'* still fun.
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Old 01-21-2008, 10:44 AM   #7
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Default TPS

If its not the IAC , vac leak, or a stuck EGR, you can try testing the idle position voltage on the TPS.
It could have gone out causing a high idle.
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Old 01-22-2008, 11:29 AM   #8
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Default Re: TPS

Quote:
Originally Posted by SSEBONNE4EVA
If its not the IAC , vac leak, or a stuck EGR, you can try testing the idle position voltage on the TPS.
It could have gone out causing a high idle.
ok when i pull out the iac am i supposed to be able to push the lil nipple peice in and out freely..? and i will have to bring it to a shop for a vacuum leak test right.?
and also would a air leak in my exhaust pipe after my catco cause a high idle like this.? thanks
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Old 01-22-2008, 04:21 PM   #9
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It has been suggested multiple times that you check or replace all your vacuum lines. I may have missed your confirmation that you have accomplished this vital step. I can tell that you are not opposed to spending money to fix the car, but I've always found it is best to start with the easiest and cheapest things first.

You could purchase a vacuum gauge and check it yourself, but you will still need to make sure all your vacuum hoses and connectors are intact and in good condition.
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Old 01-22-2008, 04:47 PM   #10
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Default IAc

Don't try the move the IAC shaft when out. Just clean and lubricate the spring and shaft with the cone.
also the seating surface inside the intake.
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