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High idle problem

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Old Jul 2, 2003 | 10:56 AM
  #1  
bigric's Avatar
bigric
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Fleet Mechanic
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From: Round Rock, TX
High idle problem

I've got an intermittent problem with a high idle. It's typically when the engine is hot. Sometimes it will idle in gear correctly at 650, but other times it will idle around 1000 (or 1300 in P or N). It may idle correctly at one stoplight, then incorrectly at the next stoplight, and then go back to normal. It's been driving me nuts. If I pull the IAC harness in either case, the idle does drop some.

Any thoughts on where to start looking? I've been all around looking for vacuum leaks but haven't found anything loose or that responds to propane.
 
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Old Jul 6, 2003 | 09:09 PM
  #2  
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bigric
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From: Round Rock, TX
High idle problem

Any thoughts on this? Anybody? I reverified the TPS voltage at idle and I snapped the throttle many times to make sure that it was consistent at rest. I'm stumped
 
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Old Jul 6, 2003 | 10:03 PM
  #3  
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1pump
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From: Oregon
High idle problem

My '92 did the same thing for a while. It would idle high, especially after a hot re-start, and the "check engine" light would come on, and the torque converter refused to lock up.
I replaced the TPS and the IAC together, and this cured the problem for about 2 years. It started doing it again about a year and a half ago, but I put it in storage in June '02 and haven't had time to investigate. I plan on driving it again next month, so I gotta fix it by then. I finally found a software cartridge for my old OTC scanner, so that should simplify the fix.
 
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Old Jul 7, 2003 | 11:33 AM
  #4  
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steve83
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From: Memphis, TN
High idle problem

Have you pulled the codes? (<-click that link)
 
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Old Jul 7, 2003 | 11:39 AM
  #5  
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bigric
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From: Round Rock, TX
High idle problem

Of course! Guess I should have mentioned that. MLPS problem (634). I just printed out an article on how to test the MLPS, grounds, etc. Failing that, I'll replace it since I'm also getting intermittent hard shifts between varying gears.

About 10 minutes ago I moved the PCV valve to the vacuum tree per a thread in the 87-96 forum and the idle quality improved drastically, but I haven't road tested it yet. I'm leaving for work in another 10 minutes, so I'll know in about 15 miles if it helped.
 
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Old Jul 7, 2003 | 11:53 AM
  #6  
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From: Memphis, TN
High idle problem

The PCV is downstream of the IAC, so it shouldn't affect the idle if the IAC is working right.
 
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