Start from square one and replace ALL of the plugs and wires on your own.
It's easy enough to do on your own.
Buy genuine FORD wires from Rock Auto.com - around $50 a set.
I've used Bosch wires because you can get a set for around $20 - but I feel that they aren't as good as the OEM FORD wires. Just my opinion...
Get some Bosch double platinum plugs, dielectric grease, and anti-seize at your local auto parts store.
Pay attention to coil pack cylinder numbering.
Use dielectric grease on BOTH spark plug wire ends - as it reduces the chance for crossfiring. Especially in WET weather. LOTS of people skip this important step...
Use anti-seize on the spark plug threads to reduce the chance of cross threading and for ease of removal down the line.
Take your time - work without distractions.
Good luck!
PS - Cracked plug was from the last person that changed the plugs.
The plugs are THIN, and require finesse when doing the final tightening as that's when it happens.
I like to screw in a few turns, then back out a half a turn, then screw in a few more turns, and back off a half turn, until I get it torqued down. The in and out turns break any dirt that is binding the spark plug threads. Sometimes the "load" you feel while torquing down is DIRT. Spark plugs on a V type engine are in a dirty area - under the valve covers.
If you're using a universal joint connected to the spark plug socket, and you're working with tight angles, be careful to keep the socket in axis with the plug, or it'll crack the ceramic insulator....
Good luck!
