Rough idle - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 4 (permalink) Old 02-19-2017, 02:37 PM Thread Starter
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Rough idle

My 2009 Cobalt LS has a rough idle, it's got 104000 miles on it and I've recently changed plugs, new MAF sensor, I've used injector cleaner on it and still no success, I've noticed it's a pretty notorious problem. I've had 3 different mechanics look at it and they all have told me they don't know what's wrong. No check engine light has ever popped on. Just wondering if anyone has any new ideas?
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post #2 of 4 (permalink) Old 02-19-2017, 02:58 PM
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Pull the plugs on the coil packs one at a time until you find a cylinder that makes no difference when unplugged. That's the cyl you want to focus on. No switch a coil and see if the miss follows, if it does its the coil. If it doesn't it's a plug or injector or mechanical damage.

Any codes?
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post #3 of 4 (permalink) Old 02-19-2017, 08:53 PM

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No codes but rough idle? How long has it done it for. Did just start recently. maybe the fuel pump is getting weak and not your not getting proper fuel flow?

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post #4 of 4 (permalink) Old 02-20-2017, 04:52 AM
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Did your mechanic clean the soot from the throttle body? This often causes rough idle and even stalling without putting out a code.
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