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

todays problem...

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Old Apr 27, 2013 | 12:07 PM
  #1  
mdlfcrss's Avatar
mdlfcrss
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Default todays problem...

Weird thing has been happening lately. Any thoughts???
91 vette, L98 6 spd...
Start the car, service engine soon lights up, car idles very fast (2000rpm), studders and sputters from takeoff, sometimes stalling.
Turn car off, wait a few seconds, restart car, no ses light, car idles normally and runs fine. WTF???
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Old Apr 27, 2013 | 01:51 PM
  #2  
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Any trouble codes?
Does it act up every time or is it intermittent?
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Old Apr 27, 2013 | 07:00 PM
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leesvet
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clean the grounds and check ALL the power source connections at the battery or source. By grounds I DO NOT mean the battery cable. Harness grounds...especially the bundle on the block by the filter.
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Old Apr 27, 2013 | 08:29 PM
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No trouble codes and very intermittent!
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Old Apr 27, 2013 | 08:51 PM
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guess the electronics won;t cause that....
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Old Apr 27, 2013 | 09:38 PM
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egr holding open??? i would think that that would throw a code? i am totally guessing here.
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Old Apr 27, 2013 | 10:08 PM
  #7  
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I'm guessing too. Its very frustrating. I'll have to try pulling codes again. If nothing is stored however.... ???
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Old Apr 28, 2013 | 03:40 AM
  #8  
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Iac?
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Old Apr 28, 2013 | 01:04 PM
  #9  
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just go thru the grounds and source connections...seriously.
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Old Apr 28, 2013 | 01:13 PM
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I'd go with the IAC and a dirty throttle body. Everytime you turn it off, pintle is retracted to allow plenty of air for a quick restart. Sounds like yours is doing that - fast idle after it's started - but the pintle doesn't extend to commanded idle and there's too much air when you drive off which makes it lean. It does however work once you turn it off and restart it. There are no codes because it's in Open Loop and the O2 isn't warm enough to show the Lean condition. Get some throttle body cleaner and spray it inside the throttle body or take it apart for a more thorough cleaning.
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Old Apr 28, 2013 | 08:06 PM
  #11  
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Originally Posted by SunCr
I'd go with the IAC and a dirty throttle body. Everytime you turn it off, pintle is retracted to allow plenty of air for a quick restart. Sounds like yours is doing that - fast idle after it's started - but the pintle doesn't extend to commanded idle and there's too much air when you drive off which makes it lean. It does however work once you turn it off and restart it. There are no codes because it's in Open Loop and the O2 isn't warm enough to show the Lean condition. Get some throttle body cleaner and spray it inside the throttle body or take it apart for a more thorough cleaning.
Is the IAC an unbolt the old and bolt in the new kind of thing or are there adjustments that need to made? I will also take a can of throttle body cleaner to it. Thanks...
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Old Apr 28, 2013 | 08:07 PM
  #12  
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Originally Posted by leesvet
just go thru the grounds and source connections...seriously.
I'll get this done too. Keep your fingers crossed!
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Old Apr 29, 2013 | 04:27 AM
  #13  
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The ECM recalibrates the IAC every time you cycle the ignition on and off.

No adjustment needed to a new one. Just push/screw the pintle all the way in before installation and cycle the ignition to recalibrate.
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