So about three weeks ago on the way back from college to visit my parents my check engine light came on and i noticed a bad misfire so i finished out the drive (only about ten miles). When i got home i had an auto part store read the codes and i figured out i needed to replace two coils, after that it ran perfect better than ever actually. Then a few days ago the misfire was back :/ i figured i may of had some water get in to cylinder 4 and 2 so i replaced the plugs it seemed to run good for about half a mile then the misfire was back, so then i thought maybe i was getting bad fuel so i replaced the fuel filter. It ran good for about two miles then the misfire again. IDK where to go next, please help oh and its a 99 5.4L f150 lol

 

This is unclear. . .

"i had an auto part store read the codes and i figured out i needed to replace two coils, after that it ran perfect better than ever actually"

So0o0o, did you replace the coils or not???

 

ya sorry, i replaced the coils

 

replace all the plugs...are you throwing any more codes with this mis-fire? make sure to use only Motorcraft plugs..triton motor will mis-fire with just about anyother plug in there.

 

have the codes checked again? Maybe other COP's are going bad...

 

reaplce all COP's and plugs..why just 1 or 2?

 

Did you use di-electric grease on the boots and contacts?

 

http://cgi.ebay.com/ebaymotors/Parts...=p4506.c0.m245 heres a set of 8 global cop's on ebay so you dont go out and spend alot of money on napa or motorcraft. and definately use motorcraft plugs. and dont forget the dielectric grease.

 

Since di-electric grease is not conductable, I thought it wasnt sopposed to be spread on the direct contacts? I thought it was just for water proofing and dry socket avoidence

 

Yep, that was the point I was getting at. If you spread it on the contacts, then it would certainly be missing.