P0300 Code. Only when Hot - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 2 (permalink) Old 07-03-2018, 02:58 PM Thread Starter
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Join Date: Jul 2018
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P0300 Code. Only when Hot

2006 2.2 Ecotec. Getting P0300 code(random multiple misfires) only when hot. Went the winter without the problem. Now that its hot and a/c is on i get the misfiring and stalls out. Runs fine when travelling down the highway. Its when slow moving and hot where it acts up. I replaced Coil pack. ECM reprogrammed. Odd thing is i repleaced the ICM on top of coil pack and the engine went misfire crazy. Same thing happened last year when i tried replacing it. Put the original ICM back in and it ran fine until temp rises to around 190 degrees. Any ideas?
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post #2 of 2 (permalink) Old 07-06-2018, 06:31 PM
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Join Date: May 2015
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misfires are caused by either bad spark, fuel/air ratio, vacuum leak, compression.
first 3 are easy and relatively easy to test/check and cheap to fix, but not compression which are usually valve related.
u said u changed all the spark plugs and coil packs. check for clicking fuel injectors and or fuel pressure, still could be a clogged or a bad injector.
use water or propane to check for vacuum leaks or do a smoke test.

using water or propane to find vacuum leaks
https://youtu.be/SI7NyfPA8V4
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