Purchased 2004 F150 late 2003. It has been a good truck up to this point when I noticed it was missing a few weeks ago. I took it to a Ford dealer and they said spark plug 3 was bad and changed it. A week later, I hear something snap and a whipping sound after the snap. The sound came from the front right corner. After that happened, I noticed a loss of power and missing again. I pulled into our shop and inspected all of the spark plugs. What I found is the plug from the same cylinder that was changed a week ago was damaged quite noticably. It looked like a pliers was used to essentially twist the end of the plug off. It also looked like a hammer had hit the end of the plug. (I have a picture but haven't figured out how to post on here yet)

Anyway, long story short, my truck is at Ford now and is going to be inspected. It has almost 30,000 miles which is probably a lot but 90% of them are highway. I would appreciate any feedback related to what possibly caused this, is this something that other Ford owners have seen before, is this something that can affect the long term performance of the engine, etc.

Thanks.

 

I bet (just my guess) that somehow that plug is getting continuous juice instead of being fired only when it's suppossed to.

 

Long shot, was the ceramic blown out of the metal part? If so, a piece of a valve could be loose in your cylinder.

Or better yet, could you have run over something that flew up and hit the outside of it?