I haven't had my 1999 f250 fixed yet. Just bought the truck 2 weeks ago for my landscaping jobs. Going to look at it today and see if either the spark plug blew out, or if the previous owner maybe didn't did not put the lube on with the plug which could, like you said, have made the coil pack go bad. All I know is I got in the truck and it missfired, made my daughter cry, then backed out the driveway, by the time I got to the end it sounded like an all out war under my hood,,,,, which brought me to you guys, and hopefully the answer to the problem. Thank you from the bottom of my heart, cause everybody says "Oh thats not good, probably a rod, gonna need a new engine." Ahhh, so thank you, and wish me luck. At least I have a little hope it's just the spark plugs, or coil pack. Peace Out Smoochie smoochie :o) Oh, and I forgot to tell you my engine light was on when I bought the truck, so I took it to Auto Zone, and they put thier meter on it and said there were missfire codes, to change the spark plugs, so I bought some, I just hadn't had a minute yet to get them put in.

DO NOT Change the plugs in the aluminum head without any threads. It's a big concern to cross thread the plug into the head and require a brand new head. Additionally if the Coil On Plug (COP) is not seated and sealed correctly with the dielectic grease, water will fall into the plug hole and cause the coil to go bad(misfire). Very simple to change out the coil (one bolt and small hands required) but costs $100 from dealer. So far the after market COPs I got on Ebay have worked for a couple years now.