5.3 with a Random miss fire code P0300

[kd6kyy]

I have a 2012 K1500 Z71 with a 5.3. it has 121171 miles on it and the spark plugs were replaced at 110521 along with the plug wires. It will on occasion light the Service Engine Soon light and the only code will be the P0300. The idle is a little rough at times but not always. Put on a scan tool and it says random misfire, however if you go through the error codes and watch the cylinder miss fires it is only cylinder 1 and cylinder 4. I pulled both plugs and found number one was heavily carboned up and the porcelain tip was carboned and cracked on number 4. I replaced the two plugs and swapped the coils with two other coils, no miss fires at this time but I suspect that the plugs will soon deteriorate and the problem will return. No unusual oil consumption and no other unusual items. I did note while removeing the plugs a good deal of oil on the threads of the plugs is this unusual?

 

[PayCeh]

Oil on the spark plugs is not a normal thing to happen. I know the P0300 typically means your intake manifold gasket is in bad shape, but that does not sound like the issue you are having. The reason you are getting oil on the plugs could be a bad head gasket, which is what happened to me in my Chevy Equinox this summer. Same symptoms. Check your coolant, if it looks bubbly and discolored I would guess your head gasket is leaking. Also, on my previous Mitsubishi Diamonte, my piston rings began to go bad and I had oil building up in the spark plugs. Check your oil levels. Good luck, I know this is pretty late response time!