p0300 Random/mult cylinder misfire (fixed) - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-28-2011, 11:09 AM   #1
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Default p0300 Random/mult cylinder misfire (fixed)

I'v got a 99 bonneville. I'm getting code p0300/ random multiple cylinder misfire with a check engine light. I can clear code, then it returns about 2 minutes after restarting. New plug wires, new plugs (autolite platinum 606 w/ .060 gap). No spark on the 1st coil pack, which I believe goes to cylinder 3 & 6. The two closest to drivers side. Replaced that coil pack (which was extremely hot for about 30 minutes after removal). Still no spark on that coil.
Car will start, but run very rough.

Is it possible for any cylinders to fire if crankshaft position sensor is bad?

Any ideas?

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Old 04-28-2011, 11:31 AM   #2
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Read this thread:

https://www.gmforum.com/obd-ii-trouble-shooting-153/p0300-284040/

Failed CPS would shut you down, not give misfires. Sounds more like the ICM. Check/clean all coil connections to the ICM.
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Old 04-28-2011, 11:45 AM   #3
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Hey thanks for the quick reply. Got an ICM ready to go. Hope that'* it. I don't want to replace the cps. Sound like too much work. I'll let you know how it turns ou.

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Old 04-28-2011, 11:58 AM   #4
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Don't forget to read the rest of the thread I directed you to. There are several other possibilities, and Danthurs provided a good write up on what to look for.

I still suspect the ICM though.
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Old 04-28-2011, 12:02 PM   #5
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Already looked at the thread. Thanks a whole bunch. I really appreciate you help. Don't know what I'd do without you guys.
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Old 04-28-2011, 02:26 PM   #6
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welcome to the forum as well
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Old 04-28-2011, 02:31 PM   #7
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Sounds like a ICM problem. I would look at the terminals. Most likely corroded. However, you pointed out the coil was hot. Which could be a bad connecting on the terminal inside the ICM causing a lot of resistance. Lets hope you didn't over load the new coil.
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Old 04-28-2011, 02:39 PM   #8
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The coil pack was extremely hot for about 30 minutes after I pulled it. Hot enought were you had to hold it with a rag. The other two were warm, nothing unusual.

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Old 04-28-2011, 02:40 PM   #9
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The new one was warm like the others after I replaced it and ran the engine a few minutes.
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Old 04-28-2011, 02:53 PM   #10
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A coil should not get hot like that. Sounds like you have a dead short. A simple test checking between the primary and secondary would tell you if that'* the case.
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