Rough Idle - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 9 (permalink) Old 03-22-2012, 01:30 PM Thread Starter
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Rough Idle

Been chasing a rough idle problem on my wife 2005 LT 2.2

Changed the plugs, swapped a new(used) coil pack, new ICM, cleaning the throttle body.

Hunted for vacuum leak (didn't find one)

Lastly the battery is going dead, Took to the car to Advance their battery testing machine, said the alternator is slowly draining the battery.


Can a slow drain cause an intermittent stumble? like a vacuum like?

Surging Idle on EcoTec board
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post #2 of 9 (permalink) Old 03-22-2012, 01:35 PM
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Is it setting a code? Because you seem to be describing a bad MAF or bad MAF connection.

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post #3 of 9 (permalink) Old 03-23-2012, 05:25 AM Thread Starter
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No codes, when it has popped a code...cylinder misfire, I changed the plugs and cleared the code. The code NEVER returned the idle on the over hand never went away.
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post #4 of 9 (permalink) Old 03-23-2012, 05:30 AM
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unplug the MAF and see if it runs the same way. If there's no change, your MAF or the connection to it is bad. If it runs worse, MAF/connection is good.

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post #5 of 9 (permalink) Old 03-23-2012, 01:19 PM Thread Starter
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It runs perfectly except at idle. I'll check the MAF sensor..
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post #6 of 9 (permalink) Old 03-23-2012, 06:30 PM
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When my cobalt was under its warranty they told me I had a bad connection to the MAF sensor, which was causing my CEL to be on, and of course the rough idle and jumpy shifting.

So, if it was the MAF sensor, I would guess the CEL would be on. I hope its as simple as a bad connection to the MAF, but its seems unlikely to me, going by my experiences and the words from service at the dealership.

Assuming your CEL is off, if its on, get free scan at autozone or which ever auto parts store offers this for free.

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post #7 of 9 (permalink) Old 03-23-2012, 07:47 PM
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Have you tried injector cleaner?

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post #8 of 9 (permalink) Old 03-24-2012, 06:02 AM Thread Starter
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THE CEL is off, when it has come on it's always a misfire which I detailed in my other posting.

I trying SeaFoam right now.
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post #9 of 9 (permalink) Old 03-24-2012, 07:46 AM
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Was it a random misfire or a particular cylinder?

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