low-load stumbling - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 01-07-2004, 11:15 PM   #1
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Default low-load stumbling

I thought I had this fixed but it won't go away!
When warm, my 94 SE will stumble (miss) with light throttle at low engine speed. It is especially noticable when pulling away from a stop with light throttle. It is also noticable at 50-70 when I ease off on the gas. I was getting bad readings from the TPS, so I replaced that. Seemed to work but the problem returned. Replaced plug wires- made no difference. It just seems like a lean spot. What should I try next? Would a dirty Throttle Body cause this? A bad 02 sensor would cause it to run rich, right?
Any experience or advice would be great.
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Old 01-07-2004, 11:57 PM   #2
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Default Re: low-load stumbling

Quote:
Originally Posted by stevej94
I thought I had this fixed but it won't go away!
When warm, my 94 SE will stumble (miss) with light throttle at low engine speed. It is especially noticable when pulling away from a stop with light throttle. It is also noticable at 50-70 when I ease off on the gas. I was getting bad readings from the TPS, so I replaced that. Seemed to work but the problem returned. Replaced plug wires- made no difference. It just seems like a lean spot. What should I try next? Would a dirty Throttle Body cause this? A bad 02 sensor would cause it to run rich, right?
Any experience or advice would be great.
It wouldn't hurt to give the TB a good cleaning. Try testing your coils and check your plugs. A new O2, plugs and cleaning the throttle body fixed mine.
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Old 01-08-2004, 05:07 AM   #3
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the warm problem may also be an indication of a bad ICM.
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Old 01-08-2004, 10:52 AM   #4
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Default stumbling

When I got the car about 3 months ago, I replaced the plugs. That seemed to make it better. If it is a bad ignition control module, why would the problem exist only at low throttle loads?- it goes away when I give it more gas.
I will clean the TB today.
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Old 01-08-2004, 02:23 PM   #5
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Weak spark. Your Alternator is putting out lower voltage at the lower RPM'*.
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Old 01-08-2004, 09:41 PM   #6
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Default stumbling

Cleaned the throttle body. It was a little dirty. It seemed to help a little but it still stumbles off idle frequently. Will check the coil packs although if coilpacks are bad, I think it would affect it under high loads and higher rpms. Alternator should'nt be a factor as the battery should compensate for low rpm volts from the alternator.
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Old 01-08-2004, 10:34 PM   #7
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The Alt can be a factor. Mine did just that. My high-rpm miss was a bad coil, the low-end was fixed by the alt. The stock 105amp alternator isn't sufficient for these cars. When they start to get weak, it'* noticeable. You need more margin. That'* not to say your problem IS your alt, but it COULD be.
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Old 01-09-2004, 09:47 AM   #8
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Default stumbling

The folks I bought the car from showed me a receipt for a new altenator. Maybe it was a cheap one! I will replace the 02 sensor next. Seems to be only do it when it warms up.
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Old 01-12-2004, 08:03 PM   #9
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Default stumbling

I've replaced plugs and plug wires, intake gaskets, cracked vacuum hoses, cleaned the throttle body and replaced the 02 sensor. Still, it stumbles below 2000 rpm with light throttle. Should I try temp sensors next? PCM? I've tested to see if I have low voltage at low rpms and the volts are fine. Help!
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Old 01-12-2004, 09:42 PM   #10
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Steve, I still suspect you have an ignition problem. I'd love to see you swap in an ICM and coils. Can you do this at a wrecker with a 'try before buy' agreement?
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