Truck problem:

I got a SES light on my dash panel and when I scanned for codes, it has a random misfire or P0300 fault. Tried checking all cylinders by testing the basics like checking the running compression and they were all fine. When removing all the spark plugs, one of them (cylinder 3) is fouled with oil. Changed the spark plug but nothing has changed. Going over the GM TSB 12-06-01-001B, there seems to be an engine oil spark plug fouling related to a defective PVC baffle in the drivers side of the valve cover. Any suggestions?

ATS Adviser:

If you see a lot of oil in the PVC line to the intake by the left valve cover, then replace it. What happens is some cylinders are deactivated ( #1 and # 7) for fuel management purposes. In the process, the killed cylinder's spark plugs get carbon build up and later fouled with oil. However, make sure to call the GM dealer because this vehicle is still covered under 100k power train warranty.


The truck is out of warranty so we ended up replacing the left valve cover and made the truck driver to run the engine harder to have less frequent deactivation. Thanks.

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