car idles @ 3500 rpm at start and 1900 rpm in drive? - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1987-1991 Parley with regards to your 1987 to 1991 Bonneville, Olds 88 or Buick Le Sabre Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 01-23-2008, 06:09 PM   #11
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What happens if you do move the shaft? I have idling problems that it'll idle at 2k or 2.5k or wherever it damn wants to, then i shut the ign off and turn it back on before the motor dies, and timing it properly [turn on around when tach hits 1.5k] will idle fine at 1k. But on first WOT run it'* back to idling funky, repeat, and we're good. Otherwise the mpg goes to about nothing.
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Old 01-23-2008, 08:57 PM   #12
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If you move the shaft you should then re-set the ECU so it will re-learn the correct idle position properly.
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Old 01-23-2008, 09:28 PM   #13
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Quote:
Originally Posted by 88bonnsse
throttle body and maf are 6 months old and should be fine but ill clean it anyway.. and then i will run some sea foam thru my vacuum line and see what happens
Real high idle like you describe is likely a vac leak or the TPS sensor (got wet inside)
Both are quite easy to track down and fix.

You can check the TPS wth a volt meter set to continuity. There are three pins on the tps sensor. Measuring across two of them (A & C if I recall correctly) will be a constant resistance regardless of the position of the throttle. Measuring from the last pin (B) to either of the other two will give you a variable resistance that changes smoothly as the throttle moves. If you do this with a voltmeter, you should see about 1 volt DC on the signal wire when the throttle is wide open. If you see any gaps in the readings as the throttle moves, then you have a dead TPS sensor and it'* driving the motor nuts.

Last thought... You say the throttle body is new (i.e. 6 months old) Check for leaks, mis-aligned gaskets, and if the throttle set screw has been messed with. There'* a set screw on the casting that the throttle bracket rests against when it is closed. It holds the throttle blades open ever so slightly and that sets the base idle airflow. Usually never needs touched...but since it is not original, and probably doesn't have the factory anti-tampering cap on it, then somebody may have screwed with it and ran the idle up.

The target idle speeds are on the emmissions label on the radiator shroud (if missing, shoot for about 800 RPM in gear with the A/C off) If the throttle set screw is still capped, then leave it alone and go back to looking for a vac leak or bad sensor.
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Old 01-23-2008, 09:39 PM   #14
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Oh, last thought...

Don't overlook the obvious...like the floor mat or a piece of carpet stuffed up into the throttle pedal. It may sound silly, but it'* happened. You can also temporarily disconnect the throttle cable at the bellcrank and see if the throttle will close a little more and bring the idle down....cables can be mis-routed, kinked, bound up, etc.
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Old 01-27-2008, 04:17 AM   #15
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Mine has this issue too... try shutting off the ign but before the motor stops hit the ign back on at around when the tach hits 1.5k falling. It'll take a few tries at first, but whenever mine idles high [50/50 chance], that'll do it for me. Replaced IAC, and it helped, but then came back. Pretty sure I got another bad IAC, but I'm a bit too lazy to take care of the problem permanently
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Old 01-27-2008, 04:41 AM   #16
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I see that its been mentioned...

Check TPS voltage at idle position, mid, and wot, be sure to watch voltage to be smooth in progression throughout. This is easiest with a SCANTOOL, but can be done with a voltmeter, although, having done this several times...can be quite a PITA.

IIRC, TPS voltage should be about .45v at idle.
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