rough idle - Page 2 - 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 01-27-2010, 08:18 PM   #11
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That'* a good point. Unplugging the TPS will be a zero signal.
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Old 01-27-2010, 08:18 PM   #12
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No, leave the TPS plugged in. Try unplugging the MAF and start it. It will run rough for a bit and then smooth out. If the problem goes away then your MAF is bad. If there'* no change, the MAF is good.
it runs rough then smooths out anyway. im kinda confused.
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Old 01-27-2010, 08:19 PM   #13
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Inspect the MAF. Tap on it, does the engine stumble? Can you see the thin wire in the MAF?
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Old 01-27-2010, 08:22 PM   #14
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i unplugged the TPS while the car was idling and i didnt notice a change in the 10 seconds it was unplugged. I didnt look for a check engine light while it was unplugged and it hasnt shown one at all since i have owned it.

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Inspect the MAF. Tap on it, does the engine stumble? Can you see the thin wire in the MAF?
its dark and cold out right now. ill check that tomorrow.

what and how should i test these parts?

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Old 01-27-2010, 09:02 PM   #15
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I didnt look for a check engine light while it was unplugged and it hasnt shown one at all since i have owned it
You haven't ever had a check engine light? When you turn the key to RUN, does the check engine light come on?

If so, then you and your car are very lucky!

If not, then your light is burned out. If you've been getting check engine "lights," then you've never been told. Plug in a code reader and be prepared for a possible laundry list of codes.
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Old 01-27-2010, 09:09 PM   #16
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The only other thing could be the throttle position sensor.
I agree. Check for codes.I have a '97.Mines looping when first started usually stalls on first start up. Hot or cold threw codes po121 TP sensor & code po108 map sensor.
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Old 01-27-2010, 09:11 PM   #17
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You haven't ever had a check engine light? When you turn the key to RUN, does the check engine light come on?

If so, then you and your car are very lucky!

If not, then your light is burned out. If you've been getting check engine "lights," then you've never been told. Plug in a code reader and be prepared for a possible laundry list of codes.
im beginning to think thats its burnt out. i had it ran for codes at autozone a while back and it had like 3 i think and i actually still have the sheets now that you mention it. thanks for refreshing my memory.

i have a P0102 code and a P0446.

so MAF it is?

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I agree. Check for codes.I have a '97.Mines looping when first started usually stalls on first start up. Hot or cold threw codes po121 TP sensor & code po108 map sensor.
mine occasionally stalls as well and i figured that had to do with the rough idle not giving enough fuel.

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Old 01-28-2010, 12:26 AM   #18
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102 is the MAF, and 446 is the EVAP vent performance. I'm thinking about a vacuum leak in the EVAP system.
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Old 01-28-2010, 05:06 AM   #19
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102 is the MAF, and 446 is the EVAP vent performance. I'm thinking about a vacuum leak in the EVAP system.
what would be the best way to test/locate the vacuum leak? im gonna take out the MAF today and see its condition and run to autozone to have then run for codes.
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Old 01-28-2010, 08:23 AM   #20
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Your just going to have to inspect the vacuum lines. Look for cracked or brittle lines.
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