1991 Buick LeSabre Custom Limited rough idling - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 06-17-2011, 02:25 PM   #1
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Default 1991 Buick LeSabre Custom Limited rough idling

Hi,

First off NO CODES, and when hooked up to a computer, nothing shows as running out of it'* parameters (using Snap-On engine analyzer, all sensors and electronics check out OK).

Driving the car runs fine, but when pulling up to a stop it runs fine then starts to idle rough.

We've replaced plug wires and IAC motor, cleaned the throttle body, cleaned the MAS (mass airflow sensor), replaced ECM (GM brand) and computer, replaced the EGR, checked for vacuum and intake leaks (no problems on either) and the problem still exists.

Tested all of the injectors just OHMs readings 15.5 when engine hot.

Car runs fantastic when running, fuel mileage has not changed, just having this blasted idle issue.

HELP!!! Ready to push it over a cliff at this point...but it'* been such a great car until this started happening, I want save it! Thanks
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Old 06-17-2011, 02:41 PM   #2
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Did you change the plugs too? What about the 02 sensors, cat and fuel filter?
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Old 06-17-2011, 02:43 PM   #3
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Rough idle is generally a vacuum leak. I would be checking all the vacuum lines, replace anything that looks suspect. Check the rubber elbows. Rub your thumb on it, if your thumb turns black, replace it.
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Old 06-17-2011, 02:52 PM   #4
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Plugs - no problem
Vacuum leaks - already all checked out
No issues with O2 sensors, fuel filter was changed, catalytic is fine

I forgot to mention this is a 3.8 V. I should also mention I work on cars all the time, this thing, though, has me completely baffled.
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Old 06-17-2011, 02:54 PM   #5
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Oh, that'd be a V6 if you haven't figured that out already - I can't find any edit button ;0

Thanks!
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Old 06-17-2011, 02:56 PM   #6
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have you pulled the plugs and inspected them? Vacuum leaks can be more then a vacuum line. A leaking gasket could cause it. Have you checked your PCV valve? A missing O ring there can cause a vacuum leak.
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Old 06-17-2011, 03:00 PM   #7
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Yes, plugs were checked, PCV checked, gasket is intact.

I'd be pulling my hair out over this problem if I wasn't nearly bald LOL


Thanks so much the quick responses, I only regret not remembering everything I've done to have put it into the original post.

Keep the suggestions coming, though, I am monitoring this as since I'm at my wits' end and saw in other threads how great this forum is, I'm pretty sure someone will bring up something I may have overlooked.
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Old 06-17-2011, 03:03 PM   #8
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Oh, there'* a new coil pack on it as well.
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Old 06-17-2011, 03:21 PM   #9
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Make sure your plug wires are not touching the wiring harness. Make sure none are touching the O2 sensor wire.
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Old 06-17-2011, 03:32 PM   #10
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Quote:
Originally Posted by Danthurs View Post
Make sure your plug wires are not touching the wiring harness. Make sure none are touching the O2 sensor wire.
Just checked, nothing'* touching.

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