I had the plugs changed at a dealer and I developed a misfire, took it and they blamed it on a speed sensor.... after laughing a bit, i recieved a gaurantee if that wasn't the problem they would diagnos for free and give me 50% on parts and labor. A week later I blew a sparkplug on my way home. Ruined a cylinder head. They had misthreaded the spark plug.

Point of the story... make sure your spark plugs haven't been misthreaded or it will be very expensive, $700 for helicoil or $3,000 to replace the head. You may have it fixed by now.

 

Well, the dealer was right so far. I changed out #3 cop and the truck runs like normal. took cop back to autozone and they exchanged it w/ no questions. lucky for them. i was fit to be tied. thanks for all your help out there