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About 3 months ago, my engine (2010 Silverado 5.3L V8 LC9) began to run rough and the check engine light came on. I checked the code and got a P0304 - misfire in cylinder #4. When I got home, I pulled the plug and found it badly fouled as show in the attached picture. I went ahead and replaced all the plugs and wires at that time. This past weekend, I pulled the spark plug from cylinder #4 to check it. It's not nearly as bad as the one pictured, but comparing it to a plug in a different cylinder, it seems to be building up gunk on the plug faster than the others. Additionally, I've noticed the the past 4-5 months that the truck has been burning oil. I don't know if they're related, but I'm throwing that in here also. From reading, it seems there are a number of potential issues that could cause the plug to foul. I've looked at pictures where they show different types of fouled plugs and the potential causes, but it's not obvious to me which category my plug falls into. From the attached picture, does anybody have suggestions of what to look into?
 

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That's a bad foul alright. #4 is an AFM cylinder. When AFM is active that cylinder isn't firing . When it doesn't fire it will build up any oil leakage getting into the cylinder. Under normal and perfect conditions it wouldn't be a problem.

Next you say you have an oil problem. The 2 are inter connected and the plug in the picture is showing at least part of the problem.

You will get many opinions on this and this is mine.... Disable AFM and get the top end cleaned. Maybe install a catch can. My guess is you got either a sticky ring or a pcv oil problem or both. Many posts available on the subject. The catch can is designed to stop sucking oil back in the motor from the pcv system. This could be at least another contributor to the fouled plug.

There are several posts on each subject and I think you should read them all. Search the following
Disable AFM
Oil consumption
Catch can
 

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I'm going to think ring being just that one and the same one. How many miles on the plug in the pic? Id try the soak or add some MMO in the oil. And see if it doesn't help. May take a little time. Water may help also. I think I'm the only one on here that likes MMO. :lol: or water :D . Always worked for me anyway. Maybe seafoam... I'm really not sure about the seafoam. That's a last resort for me... seams a little to aggressive for the crankcase and smells like isopropyl and kerosene.

Anyone favor the Seafoam?
 
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