Clyinder 8 Misfire? I've tried everything I know
 

This problem I'm describing in on a 98 F150 4.6

I was getting a Cylinder 8 code so I changed plugs and wires. Then on a trip to Missouri from Wyoming I got a Lean Bank 2 code and another Clyinder 8 misfire code. So I've fixed my exhuast leaks and replaced the fuel injector for that clylinder. And the misfire code is still on??? The spark plug was cracked when I checked it the second time put so far the new one is fine.

I'm lost on this one. Usually I can trouble shoot anything on my truck, but I'm lost. I haven't switched the coils yet to see if the misfire moves. And I need to check the timing.

I've heard this could be a compter problem with a short somewhere. Is this true. What else can I check?

Any ideas that would help me out. Thanks

I'd try changing the coils and disconnecting the battery for a bit to reset it. Then hook it up and see what happens.

My mom's 99 5.4 had that problem. After chasing it for a while, her mechanic found it to be a coolant leak was shorting out the coil pack.

Open up your hood in a dark garage/on a dark night, and see if you notice any plug wires arcing.

I had this same problem and after changing just about everything I put on a set of 9mm Ford racing wire which solved my problem.

Yep, like the old 460 engines etc where you'd have to keep the wires that fire one after another away from each other, like 7/8.

Make sure the wires aren't close to the AC accumulator. There are posts on here describing this problem that I think apply to your truck and how to remedy. I would definitely look at replacing the coils.

get a v6

well since you havent checked fire id say that first but ive also seen injector wires break where the wires go into the loom and right at the connector.

K we checked everything the plugs wires and coils all passed. So we did a compression test and cylinder 8 failed miserably. So know we are going to have to go internal. thanks for the help

Probably a cracked valve as the spark plug was found damaged in orginal troubleshooting.



The truck has 1992-1998 standard heads. Can I replace those with the 1999-up Performance Improved (PI) Heads, without changing pistions?

Had same problem on my 97,#8 cylinder also. Found an old tsb from ford about condensation in spark plug well,it said to coat plug wire boot with di-eletric grease throughly before installing,this will keep moisture out. I did this and have not had any other issues. Previously installed new wires also before I did this.