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Higher/erratic idle after warm up?

Old 01-31-2013, 01:41 PM
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Higher/erratic idle after warm up?

Hey guys I have a question. My 91 L98 car has been giving me an issue the last few days. It seems like when the car warms up a bit the idle goes up like a vacuum leak. with my foot off of the gas the car has a erratic miss. I've tried to track down a vacuum leak to no avail. I've read that sometimes a stuck egr valve could cause this. I haven't pulled the plenum off yet to check. What else other than a leak could cause this condition? any help could be great.
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Old 01-31-2013, 01:46 PM
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Re: Higher/erratic idle after warm up?

stuck egr will do that for sure. built up crud in the IAC circuit will too.
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Old 01-31-2013, 07:30 PM
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Re: Higher/erratic idle after warm up?

HOw do you check the EGR valve- 'unstick' it??
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Old 01-31-2013, 08:01 PM
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Re: Higher/erratic idle after warm up?

I've never had to do my camaro, BUT my blazer used to do this all the time....remove it and take a look at the valve opening. you should be able to see if there is some black carbon chunks holding the valve open. they are supposed to be closed at idle....any opening at all will kill your idle..
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Old 02-09-2013, 12:12 PM
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Re: Higher/erratic idle after warm up?

Unmetered air could also cause this. After you've checked out the EGR, if the problem persists, look the intake over carefully for any air leaks.

BTW, due to the location of the EGR valve on The F-body L98. It may be more reasonable to perform a vacuum lift test. To do this, use a hand vacuum pump attached to the hose going to the EGR valve from the EGR control solenoid. With the engine idling, apply vacuum to the valve and look for the idle to drop off and the engine to stumble or even stall. Then release the vacuum and see if the engine still idles high and uneven. If so, it's probably not an EGR issue.
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Old 02-09-2013, 12:38 PM
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Transmission: Probuilt 700R4 3600 stall/ T5
Axle/Gears: Moser axles, 3.42 Eaton Posi
Re: Higher/erratic idle after warm up?

I actually figured out what the problem was. My TPS sensor decided to go south on me. Luckily the car managed to turn on the SES light and it gave me the dreaded code 22 lol. Another score was I got an adjustable TPS sensor from a buddy of mine for free so now it runs better than before. I still need to adjust it better to "fine tune" it and set the minimum idle but the snow outside is kinda holding that off for me.
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