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

Continuing Idle Problem

Old Apr 24, 2006 | 06:19 PM
  #1  
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Now im really going nuts, I just cleaned the TB and the IAC--put it all back together adjusted the IAC allthough when I was ajusting the idle the car kept going from about 450 to 700 rpm up and down. Then to theTPS ok at .568 and smooth all the way to wot. Ok I start the car and get a fix selective ride light and the car dosnt idle worth a crap. I disconnect the battery and wait then go for a 25 min. ride, fast slow the whole 9 yards--get back to the house and it is rattleing my 1 brain cell that I have left. The car runs so strong as long as you give it gas--if you try to go steady about 2 grand its bucking all over--touch the gas and it goes great and smooth as can be. It wasnt this bad before the flywheel change--sorry guys but I cant allways be WOT. What do you think is my next step-besides harry karry plugs have 500 miles on them -cap rotor and wires where in the car when I bought it,so you never know-ok ill shut up now -You guys have been a great help so far what do you think about this?
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Old Apr 24, 2006 | 06:41 PM
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Sorry this is a1990 L98 and no codes
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Old Apr 24, 2006 | 06:58 PM
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I had the exact problem on my 90 this spring. Turned out to be a vacuum leak. Idles great now.
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Old Apr 24, 2006 | 07:02 PM
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Sounds like you have a vacuum or plenum/intake leak. When you adjust minimum idle, the only air that should get into the plenum is that coming through the butterfly as you turn the screw. With your idle surging, air is getting in from somewhere else. Check vacuum lines - and/or - you can use a little propane from a plumber's torch (don't light it!) and aim it at the sides of intake and all round the plenum and runners - if it really speeds up, that's your leak.
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Old Apr 24, 2006 | 07:11 PM
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I did the propane thing all around and even all the emissions lines to the point where I thought the garage would blow up. Thats what is driveing me to drink(which isnt all that bad) but I cant figure it out. I have tried all the things in the FAQ but none worked so far --nothing I do is simple--your saying that it should not be surgeing up and down with the IAC disconnected?
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Old Apr 24, 2006 | 07:19 PM
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Check HERE for suggestions.

RACE ON!!!
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