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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 10-31-2013, 07:52 PM   #1
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Default Rough idle

Hi all

I was driving down the highway and ran into some traffic car started running rough. Acceleration is rough. Feels like it gets worse the longer since it idle.
Almost like she'* running on four cylinders set of six
anybody run into this problem before.
thanks
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Old 10-31-2013, 08:31 PM   #2
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Try pulling the idle air control valve and clean up any carbon. Check for any vacuum leaks by spraying carb cleaner on the hoses and connections. If there is a change in RPM'* you found a leak.

Sounds like a vacuum leak to me.

If that doesn't work, disconnect the wire connection from the MAF sensor. If that clears up the idle you need a new sensor.
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Old 10-31-2013, 09:20 PM   #3
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K

I'll check it out. On my tBI truck it did the same thing. Ended up being my icm
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Old 10-31-2013, 09:49 PM   #4
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the icm could be heating up and going out, also could be wires or plugs, though those normally make it run rough at idle and when at cruise more than acceleration. could be maf too but hard to see if its reading correctly without a scanner
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Old 11-02-2013, 12:56 AM   #5
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Any reason why this spark plug tester would not work to check the coil connections?

Inline Ignition Spark Checker

I have some time tomorrow to work on her.

Also I took her out again today for a little test spin. She started ok, but soon went rough. Has a hard time accelerating.

Really noticed it on uphills or trying to slowly accelerate above 50. Feels like she just wants to stall.

Thanks again everyone for all your help.
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Old 11-02-2013, 08:21 AM   #6
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i imagine its getting spark since you didnt say anything about misfire codes. one thing you could do is mist some water on the wires and see if its worse, then its the wires, i would look at the plugs as well and check the coil terminals for corrosion
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Old 11-02-2013, 04:13 PM   #7
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First off, thanks everyone.

Ended cleaning the MAF sensor, and she'* running MUCH better. Would this be why my gas milage is around 21 MPG doing mostly highway?

Also my O2 sensor is about 5 years old and it what WHITE! Very lean condition.

So after I cleaned the MAF, my acceleration resumed and I could barely feel any hesitation. it'* still a little there though.

So is it time to replace the MAF sensor?

Thanks!
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Old 11-02-2013, 09:59 PM   #8
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First question should be is, when'* the last time a tune up was done?
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Old 11-02-2013, 11:32 PM   #9
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Plugs n wires are about 3 years old.
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Old 11-03-2013, 06:00 AM   #10
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If they are that old, then I suggest a full tune up be done.
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