Just bought 06 f150 with 5.4 and having coil problems i am noticing that the coil itself tests fine but i have noticed that when i pull the boot off of the coil, and i use a light and look at the area where the spring is inserted into the coil that the small tab in the center that the spring attatches to has some corrosion on it, which is likely the cause of the failure, i believe the coil itself is fine just the connection between the spring and coil which is bad, i tried cleaning but was unsuccessful, i have been filling that area with some electrical insulating compound (dielectric grease) to keep moisture and oxygen out, i have two that have failed thus far, and i've only owned the truck for two weeks, i'm thinkin i am gonna change the plugs just not sure if i should go champion or stick with factory, i noticed the accel coils are alot cheaper as well, but i have been a heavy duty mechanic for several years and sometimes the aftermarket stuff aint all its cracked up to be.

 

smokingunn, I changed my plugs to the #7989 Champion and also the coils with an Accel set from Summit Racing. I have over 17,000 miles on them with no problems. You could use the Motorcraft and follow the TSB. Also Accel now has a plug set for the 5.4-3V engine (AP4346S) which may be made by Autolite. It is compared to the HT1 plug.

 

Well i have a cylinder 5 mis fire, tried a different coil, no change, gonna pull the plug and see what it looks like, i bought a set of champion plugs, its nearly due for a set of plugs anyway, if not that maybe an injector.

 

well pulled the plugs, they looked great, but changed em anyway, still number five miss fire, i pulled the injector out and cleaned and installed again, no change still misses at wot, i removed the plug from the coil, at an idle and it dfinetly starts to shake, and the engine is definetly not missing at idle only at wot, do i change the injector? i'm thinking the compression is ok as the plug had no build up on it, the only thing left is the injector, if anyone had any other ideas they would be appreciated.

 

well turns out my catalytic converters were plugged in my truck and was causing the exhaust valves to float, pulled em out and truck runs like a top.