I have an "01 F150 w/Triton 4.6. Have had a miss for a while. Check engine light came on. Had it scanned , came back that #6 cylinder was missing. Replaced all plugs and coil for that cylinder. Still missing. Replaced all 8 coils, still missing. What else could it be?

 

If the code didn't change after replacing the # 6 plug, boot and coil and no other codes came out with a scanner check, you should have changed a blocked or faulty fuel injector for that cylinder assuming the plug to it was fully seated..

 

First make shure you aren't getting water or something in that plug hole. then I would take all known good components Plug, coil, and injector from a cylender that hasen't set a code and exchange them with the bad cylender then drive it if it still comes up with the same cylender then you either have a wiring problem (check all conections at the coil and injector large conector to main harness and computer conector) if wiring isn't an issue than the computer may have a bad injector driver or coil driver.

 

Have you performed this fix yet (thread link below)? It made all my problems go away with my truck. I was experiencing similiar symptoms to what you have described. If nothing else you will know it is not the problem...

https://www.f150online.com/forums/v8-engines/5621-fyi-5-4l-f-150-owners.html

 

Guys, Thanks for all the advice but I've tried everything. Took to mechanic, he said I've either got a computer problem or a wiring problem. Constantly gives reading that #7 coil is bad, but plug and coil have been replaced. What else could it be?

 

check for a coolant leak from a rad/heater hose. this could be leaking on the plug and causing the miss. might need to just replace the hose and and clamps..

http://forums.fordpower.ca/showthread.php?t=3359
a user on my site had the same problem.

let us know how it goes.

 

A missfire detection is a code P0307 for cylinder 7.
What code is still set?
There are other cylinder related codes depending on the year of the engine and equippage.
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A missfire detection can't tell the difference between a bad plug, boot, fuel injectors or intermittamt wire problem.
Why, because the method used to detect missfire is time based on crank rotation. Any cylinder that contributes less power (for whatever reason) will slow rotation a small amount. This is measured by the cam/crank sensor.
The decision to set a code and call a fault is by reference to a table in the PCM program that is even modified over time as the engine wears and cylinder pressures decrease.
It could be the PCM but I would at the least swap position with two injectors to see if the fault moves.