PAULLY77

04 f150 5.4 litre engine,i put those funky looking plugs in and now i have a serious engine miss..also i replaced every coil pack on every plug...

BadFish523

Do you have any codes? What brand of plugs? Did you clean out the carbon build up where the old plugs were? Did you use dielectric grease on the boots? Have you checked all the connections?

SCORGE

Proper torque?
Brand name of plugs?
Cleaned any and all debris from well before installing?
COP connections fully seated and clean?

BadFish523

I know.... Lots of questions. We're just looking for as much information as possible or else it could be any of the things we've listed so far. We're here to help, not trying to overwhelm you.

Tom Werner

Well, don't discount the basics... I replaced all the plugs on my 2004 XLT with a 4.6L, and there was an obvious miss.

I wound up replacing all the coils, and the miss persisted. I bought a spark plug tester, and a fuel injector circuit tester, and everything tested fine.

finally, I took it to a mechanic, who told me that two of my spark plugs were cracked.

I torqued them correctly with a torque wrench, so it is likely they were cracked in the box and I did not look closely enough prior to installation.

So, the lesson I learned, is check your work. Even if it is new, it doesn't mean that it can't be the problem.

Tom

redfishtd

Check your vin and use mc plugs and new boots .

MilosF150

Without a device called a 'megger' (Mega Ohm meter) there is no way to detect a cracked ceramic shell. Meggers are not cheap so its not a tool most ppl have around.

In the old days we would just grab the boot... it you got shocked, then the plug was bad (you were a better ground then the plug).