At 80,000 miles I had the plugs changed by the dealer. Changed the oild and went on a trip to California and back. Any time the truck was under load it would idle roughly until it was shut down and restarted. After I got back I started pulling plugs and found the #6 had been destroyed, no tip left. Apparently it was sucking oils up through the tube (pcv) on the left valve cover and into the number 6 cylinder. Replace the plug and did some research on here. Ended up buying and replacing the left valve cover. Didn't solve the problem. Currently at 103,000 miles.
Any ideas from anyone that's had a similar problem?
Thx.

 

If oil is getting into that cylinder, it would just carbon up the plug, not burn the tip off. Things like that cylinder running lean would more likely cause the tip to burn off from overheating. After it stopped firing, then it got covered in oil. I would suspect a clogged injector. Are you getting any CE codes?

 

Check engine light is on, no code logged. Seems to be pulling oil in from the pcv hose and dumping it into the manifold above #6. Plug was wet from oil when I changed it. The one that was burned up was after the 1800 mile trip back from CA. No excessive sludge was noted when I changed the left valve cover. Actually pretty clean for 103,000 miles. Seen much worse. Getting ready to disconnect the hose and block it off and see if it helps any. If I kill a couple of whales, Oh Well.

 

Would or could a clogged injector be intermittent?