I hesitate to introduce auto info to the forum, but vehicles are integral to our activites.
I had to rescue 8 members of my family after my 2003 expedition with a 5.4l gas engine blew the spark plug right out of the block at 80 K miles. Apparently it is a common problem. I suggest searching "ford blown spark plug".
zillions of pickups and expeditons manufactured betweem 97 and 03 have the same issue. Ford is well aware of the problem, but will not adress it.
While there are obviously lots of these engines having no problems. the major anchorage area ford dealer I work with sees "one a week at least".
The repair runs between $3,500 and $5,200. Given this price I am actually flying a mechanic in from San Diego july 28th to try use technique. more on this later.
In the mean time forewarned is forarmed.
And PS if you already have issues, PM me the mechanic has lots of extra time. I'll probably try to catch the late red run with him.