wally7381

hello all, I am working on a 06 f150 5.4 for a customer the problem I am having is vehicle is running rough when at a stop sign. then when you accelerate starts running fine and may or may not come back at next top. when the check engine light comes on and starts to flash I get a code for a misfire on #5 cylinder, when I shut the vehicle off and start it back up code is gone and runs fine for awhile. so I swapped #5 plug and coil with #1 and retest drove after clearing codes. still miss firing on #5 cylinder so I swapped injector #5 with #6 still misfiring on #5 so I did a compression check on all cylinder and all with in norm (133psi -138psi) #5 was 133.5 psi. so then I was told to try disconnecting the battery for awhile to rest computer so I did and let set over night next day hooked battery back up and drove still missing on #5 cylinder. any other idea would be greatly helpful. I have also tried cleaning MAF, checked for vacuum leaks.
thanks wally7381

primalurges

Try leak down test on 5. Might be valve train issue perhaps a burnt valve. Any engine noise? Also, don't rule out a bad spark plug.

wally7381

Sorry took so long but did leak down checked ok . It does have engine noise sounds like spark knock. Was told it mite be cam phaser siloniods replaced them not it. Tried powering siloniods while engine running and have same symtoms while powering siloniods so cam phaser seem to be working

primalurges

Did you change plug on #5?

wally7381

Yep plugs,coil

Elkmagnet

My next thought would be the coil or injector wire harness.

wally7381

Ya mine too that's what I'm checking now thinking pcm

forayzor

Monitor base engine oil pressure when concern happens, right at the port on the oil filter housing.

wally7381

Did oil test 60psi

muddyF-150

doubt it is the pcm.. check the voltage and resistance in the wire harness. might be a short somewhere or corrosion on the plug to the coil..