LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

high idle

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Old 06-26-2007, 08:21 PM
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high idle

My car is idling at about 1200 rpms, and when Im slowing down it goes to 2k rpms and stays there until I come to a complete stop. I have changed the IAC and it still does it. It drives fine, and there is no SES light. Any ideas?
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Old 06-26-2007, 09:12 PM
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I am not sure if this will help, but I know the FBody tachs are off by +200 rpms.
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Old 06-26-2007, 10:35 PM
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Yeah, but its been higher than usual lately. Throttle body maybe?
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Old 06-27-2007, 05:31 AM
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What did pcmforless set the target idle speed to? How much has it changed?

A scan would tell you if the IAC valve has closed all the way down and can not reduce the idle speed. That could indicate a vacuum leak or blades that are not closing fully. Have you checked for vacuum leaks? Have you verified that the throttle blade shaft is rotating freely, and the blades are fully closing when you lift off the throttle? Have you checked the throttle body for sludge buildup that may be restricting blade movement?
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Old 06-27-2007, 10:15 AM
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Idle speed is set at 850. The tach has always been right at 1k rpms at idle. Now it stays at 1200 at idle. Its alot worse with the ac on. I tried spraying cleaner in the throttle body but it hasn't changed. I'll check and see what the IAC counts are. Also, I backed the idle screw off and it still does it. I haven't found any vacuum leaks.
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Old 06-27-2007, 01:43 PM
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My TB used to stick open a bit, causing a high idle. Removing it and giving it a good cleaning and some lithium grease fixed it up.
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Old 06-27-2007, 06:14 PM
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I didnt get a chance to put it on the scanner today, but I will definetly take it off this weekend and clean it up. I hope that solves it. If not, time to upgrade!
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Old 11-09-2007, 07:05 PM
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My car is doing this exact same thing, but I am stock. I have changed the IAT and the coolant temperature sensor. It still idles high! God Damned annoying! Help!!
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Old 11-09-2007, 09:42 PM
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had the same problem with my 95Z, backed the idle screw out a bit and now its fine i tried cleanin it too with no luck
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Old 11-11-2007, 12:01 PM
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Originally Posted by Maroman88
had the same problem with my 95Z, backed the idle screw out a bit and now its fine i tried cleanin it too with no luck
This screw of which you speak is on the drivers side of the outside of the throttle body, right? It stops the blades from closing all the way. Or is there another screw?
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