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post #1 of 5 (permalink) Old 12-20-2015, 04:54 PM Thread Starter
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Intermittent Misfires

I have a 06 cobalt with a new engine and the this problem is driving me batty. It runs great then it random misfires every so often at mid rpms about 2500 or 3000. Sometimes I can go for a hour before it will miss and sometimes 30 seconds, it stumbles then goes back. I can re create it by reving the motor in neutral and it will miss eventually. Now heres the confusing part, all I get is a Po 300. And I can make it not miss by unhooking the maf sensor then I cant make it misfire..... I replaced the maf sensor with a used one from the junk yard and it does the same thing. Also when it does miss it goes into open loop then when it goes back into closed loop the misfire is gone, Ive watched the scanner and checked sensors and replaced lots of parts but I am getting no where with it, is there anyone who may have any idea what may be causing this????
I have a 2.2, new injectors and pump. went through looking for air leak and there were none, new seals on intake. new 02 sensors new plugs, coils. Swapped out maf and map. great compression, po300 was on cylinders 2 and 3
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post #2 of 5 (permalink) Old 12-20-2015, 05:39 PM
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The 06 has 2 spark coils on top of the valve cover with ignition module if I remember correctly. One sparks 2&3 and the other sparks 1&4. Is that a new ignition coil or a junkyard thought to be good? P0300 is a multiple misfire code and normal when you lose one of these coils. A bad spark plug or an 07 up would give you a more precise code like P0302 or P0303. My guess you have a bad contact between the coil assembly and the ignition module or your coil set is bad.

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post #3 of 5 (permalink) Old 12-20-2015, 05:43 PM Thread Starter
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Sorry I neglected to post it but new coils and modules and no change, the maf sensor was junk yard
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post #4 of 5 (permalink) Old 01-06-2016, 08:05 PM
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CEL code P0300 and P0301...2008 Colbalt

We have 2008 Colbalt. We are getting CEL code P0300 and P0301. Misfire cylinder 1. Seems like ignition coil bad. Any other ideas out there?
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post #5 of 5 (permalink) Old 01-11-2016, 07:58 PM
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Mine was missing on cylinder 2 intermittently. I moved plugs and injectors but the misfire stayed. The repair ended up being an engine Dearborn treatment and a crank variance reset. Sorry that I did both then drove it but I believe the reset was the issue.
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