C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

high idle

Old Sep 18, 2002 | 11:32 PM
  #1  
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Default high idle

What would give you a high idle with no codes? Car acts like the throttle body is dirty - cleaned it 3 times and looks really clean. When driving it wants to hang high. Will come down to normal blipping the gas, then do it again time after time. Seems to love to go to 1800 - 2100 rpm. Talked to several mechanics and have no leads at this point.
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Old Sep 18, 2002 | 11:51 PM
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Default Re: high idle (Grouchy67)

Don't know how much this is good for but today after starting the Vette the idle would not drop below 1100 rpms. I opened the hood and noticed the fan was only running at half speed so I played with the wire going to the switch and the fan went to full speed and the idle dropped instantly to 6000. :confused: :crazy:
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Old Sep 19, 2002 | 01:45 AM
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Default Re: high idle (Grouchy67)

Have you tried replace the TB with a new one? MAD has the 52 MM ones for only $300. You can always send it back if it doesn't fix the problem. They are easy enough to install.
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Old Sep 19, 2002 | 02:32 AM
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Default Re: high idle (dbwade36)

TB shaft has extreme wear on the connection side (acel & cruise connect area). Approximately 1/8 to 3/16 play. But the spring closes the butterflys & 2 different "professional" mechanics assured me that the TB is not the problem.
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Old Sep 19, 2002 | 09:47 AM
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Default Re: high idle (Grouchy67)

from what i have read in your post, and read from other posts, it is the T.B. the shaft is simply to worn out, mine was the same way, just not as worn, a little lube has it fixed for right now. Apperantly the vacuum from the engine will pull the butterflys open a little and... increased idle.
Im sure others will chime in as well, but thats what it sounds like. my 0.02 worth anyhoo.
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Old Sep 19, 2002 | 11:23 AM
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Default Re: high idle (LarryK 87)

Yup mine's that way too and my divorce is taking all my money right now so I put a second spring on it for the time being :seeya
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Old Sep 19, 2002 | 01:43 PM
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Default Re: high idle (LarryK 87)

I had the exact same thing with mine. Replaced the TB with a 52mm from TPIS and the idle is now perfect. If you replace, you should follow the instructions out under Tech Tips for setting the base idle. Also if you have it all apart you might want to do the TB bypass...
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Old Sep 19, 2002 | 03:20 PM
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Default Re: high idle (Grouchy67)

Thanks for all the input. I needed other opinions. I thought it was the TBI but the "professional" mechanic opinions really confused the issue.
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