i just picked up an 06 f150 with 5.4l 4x4 xlt package. Love the truck as it is my 1st Ford HOWEVER..... the truck is running super rough at idle and keep getting code for cylider 5 misfire and bank 2 lean (which i am assuming is from cyl 5). here is what i have done so far...

New Coil packs
New spark plugs
New fuel modual
New fuel injector on cyl 5

for the life of me i cannot figure this thing out. Still has a "stumble" when accelorating around 45 mph and shows code for cyl 5 misfire then will then throw code for bank 2 lean.

i have read several things online but they all seem to talk in circles about the same subject. PLEASE HELP!!!!

 

What brand coil packs and plugs? Where did you purchase coil packs?

I dropped a plug on install, inspected and installed. Turned out there was a hairline crack that caused misfire. Took a little time to figure that out, and crapped the cat in the meantime due to excessive unburnt fuel being passed through.

At the same time I replaced the coils, just for the sake of PM, and ended up causing more problems. Took a while to figure it out, but the Motorcraft coils I received from Summit were not all the same though they all had the correct number on the boxes. Only half of the coils shared the same Ford engineering number as my originals. The result was that the engine ran fine for a while, then developed a miss. Summit replaced the specific coil and resolved the problem, for a while. then another cylinder would start missing. Eventually I disvovered the P/N difference. Reinstalled all of the original coils and have had no problems since. So much for doing PM. Ha.

Sometimes non-Motorcraft plugs have been replorted to cause problems too.

 

the plugs are MOTIONCRAFT and the coils were purchased from autozone. my buddy i bought the truck from said he only replaced 5 of the 8, but cylinder 5 was changed and after reading your reply i do know that the one one 5 is grey compared to the others being black, i will check the numbers on them when i get out of work today. any other issues i should look into? or do you think that the coil on 5 could be different than the rest and need to be swapped back?

 

you had also mentioned that you "crapped the cat" how could i check that? wouldnt it be throwing codes for the cat or o2 sensor? i cleared codes and everything came back complete but is showing pending code for cyl 5 misfire again.

 

You may want to inspect your throttle body. I had problems and I had to rebuild my throttle body

 

Mine had a code for the cat below threshold. Forget the number. If you have another coil that you think is good, swap it. Or just swap #3 & 5 or similar and see if the problem moves to the other cylinder. My misfire was never consistent, but if I drove it long enough it would do it when at low RPM under load, like just starting uphill before the tranny downshifted.

 

Can you please describe how you diagnosed your throttle body , and what parts you replaced ?

 

I cannot remember the cel numbers, but I have a really good buddy thats been a ford service tech for 20+ years he said alot of times when your battery dies it messes the throttle body up and you have to replace I think the 2 censors on it. Thats what he did with mine and it cleared up the problem and no more cel

 

Also I do recall bank 1 or 2 running lean I believe

 

Well i swapped coils around and is still showing pending code for cyl 5 misfire. I looked for bad vacum line, made sure there was dielectric grease on the connections on injector and on the coil. Cleared the codes and truck seemed to run smooth but rough idle came back again. Someone had told me that it mite be a bad cat due to the misfire. Is there a way to narrow that down woith out costly tests at a dealership? Also the only time while driving that you can feel the miss is around 45 mph when it is about to shift out of overdrive when accelorating.

 

Well the easiest way to decipher if your cat is bad or not would be to visually inspect it..IE remove it from the truck or use a scope through an 02 sensor hole.

Bad misfires are the number 1 destroyers of catalytic converters. My father's 2000 5.4 had stumbling in Overdrive only. If you turned off overdrive it ran fine. I replaced all 8 coils at one time (since the code only came back as random misfire) at he hasn't had an issue since. I was gonna replace the cat first but the fact that it ran fine through the rest of the gears made me think otherwise.

I really didn't feel like trying to figure out which coil it was, he had the money to buy all 8 so that's what I did, to this day I don't know which cylinders were the culprit.

Clear that pending code again and make sure it comes back. You may also want to try to examine the electrodes on the spark plug to try and figure out what's going on with that cylinder, as well as a compression test at that cylinder.