Scotty,
I have a 2003 Ford F250 4X4, auto trans with the 5.4L engine. While driving a few weeks ago the truck felt under powered and once I stopped at a traffic light, I could feel a miss. No check engine light so I pulled the spark plugs and found cylinder 3 had melted the spark plug tip and ruined the coil pack.
I replaced the plug and coil on #3 and also the fuel injector. However when cold starting, this cylinder misses until it warms up after about 1 minute. After that it runs fine and has normal power until cold again. This spark plug ejected 8 years ago but was repaired using a timesert. Haven't had any problems until this. Wanted to know your thoughts on what to do next, or what may be going on. Thanks
Those helicoil inserts can be a little funky. It’s probably leaking until it heats up and expands then runs fine. The fact that you had plug damage tells me it may not have melted but might be sitting to deep in the cylinder. You can pull it and try a new insert, but If you are mechanically inclined I would find a head in the junkyard off one with low mileage and install it onto your engine. Just take it to a machine shop first have them clean up the block side a little and flush the oil and water jackets on it first.
