I have a 06 with a 5.4, at 60,000 the #8 cylinder was bad and I had to replace the block. Now with a brand new motor I keep loosing the coils on # 5 & 7?
I put a new coil on reset and all is good for about 100 miles and then check engine light comes on , I check and 5 and 7 are bad again...

Any help would be appreciated , thanks

 

I would suspect a problem with those 2 spark plugs.

 

Or the boot.

 

Don't new coils come with boots?

 

I don't know, I assumed they didn't because I never bought one. Don't have much use for them on my 4.2

It may depend on what you buy, and where you get them.

 

They come with boots, just like spark plug wires.

Dielectric grease is required when you install coils.

 

thanks, I did not grease , would that cause the short??

 

I can try that, but plugs were brand new with motor

 

were the injectors brand new or reused?

 

Is the truck missing when you get the code or is it just a code with no symptoms? I had a miss a few months back, so I replaced the coil and the miss was gone. A few weeks later a code popped up saying miss on the same cylinder, but it was missing so I cleared the code and no problems since.

 

What brand are the plugs?

 

its a roush with the supercharger

 

hto , colder plug direct from Roush

 

Cold Autolite plugs? They may be fouled.