3 weeks ago I replaced all my spark plugs, I did NOT replace any of the coils. My truck was running rough and replacing the plugs corrected that problem. This past weekend I get a check engine light that shows I have a misfire on 4 & 7. When I changed the plug on 4 it was burnt beyond belief. The plug on 7 was just fine. So I replace the plug on 4 with another plug and I replace the coil. I do the same on 7 yet I still have a misfire on both and the engine is running very rough. I took it to a shop and I have good compression in both and they swapped fuel injectors around but still misfire on 4 & 7 only. They were a small shop so they did not want to go deeper so they gave it back to me still not running right. Could this be the computer causing this issue ? I can't find anything on-line of someone having the computer cause this much grief. I hate to take it to my local Ford shop because I know I'll be looking at a large bill. Any suggestion before I throw my check book to the wolves ?

 

Which engine and what brand plugs and coils did you use?

 

2WD 4.6L
I used the ACDelco coils and plugs.

 

AC Delco coils are okay, but spark plugs are a lot more fussy. You should be using Motorcraft plugs. You have a Ford, not a Chevy!