This has me completely confused!! 97 F150 4.6 liter Windsor engine base model truck manual transmission. Code for misfire cylinder number 7 constantly comes up. I have changed all spark plugs plug wires coil packs sensors virtually all of them except oxygen sensor reworked the head with new valve seals completely cleaned valves are perfect unbent perfectly clean brand new Pistons because the Pistons had broken rings new bearings the whole nine yards And the Gang code came up again. Fuel injectors I've even switch them from one cylinder to another spark plug switched cylinder to another the code still comes up with 7 I've already put in a new computer that one has also been flashed for this truck. I'm thinking the only thing left is the actual wires themselves. But only one pinched wire out of all eight cylinders. Help if anybody knows. Len

 

Have you looked at your fuel trims with a scan tool and checked for a vacuum leaks on the intake manifold?

 

No leaks, engine was completely rebuilt. Sounds great, runs great, 20 miles into a run the light came on again. It had been coming on between 140 and 148 miles. Now I am thinking it is the computer again. This is the second one. I still have the original. I just jumped the wiring harness and will not have a light till i run the 150 miles tomorrow. Hopefully not!! There is no setting for a fuel trim that i can find for just 1 cylinder. Thanks

 

This is like trying to perform brain surgery through a telephone conversation.

You need to read up on fuel trims and what they actually are what they do and how vacuum can affect it. I think you are just making assumptions because everything has been "rebuilt" as you say but there is no proper scan diagnosis being done here.

Unless you have a high level scan tool to check both short term and long term fuel trims and seeing if you are running rich on your O2 sensors that "may" be caused by a vacuum leak, you really are pissing in the wind trying to figure this out by "20 Questions" on the internet.

Good luck, wish you well in whatever you find.

http://www.easterncatalytic.com/educ...agnostic-tool/

 

I recall an issue of this nature having to do with the PCM not having the latest calibration. Only way to be sure is to have to have the truck hooked up to the dealers diagnostic equipment or someone with IDS so it can read it. Just because you have a new PCM doesn't mean it has the latest software.
.

 

just a quick note to all of you folks up there at F1 50. The wiring harness that wraps around the engine for the fuel injectors can and might have pinched wires. I have just finished repairing three wires on the left side(drivers side). One, the red hot wire, two, the tan/red for cylinder 7 and third, the red/lt blue to the ignition coil. All were worn in the junction of the 7 cylinder location. No more misfire! Thanks.

 

Congrats.

If that happens at idle too, well thats what noid lights are for.

Ignition analyzer will also show high resistance from lean mixture. All just by holding a doodad near the coil. Black magic I tell ya.