Grt66

I have been chasing a misfire for while now and the only thing I know for sure is that it does it worse on days when the air feels damp. I have change plugs and cops.
06 5.4 XLT.
Any ideas?

gonzo8000

Ckeck the FPDM fuelpump driver module

Grt66

That's been changed.

otto457

Did you use dielectric grease on the COP boots? And are you sure you didn't have a dud COP out of the box?

Grt66

I used dielectric grease and I have swapped cops around.

hcbph

Used to own a car that had similar issues. I bought some LPS Water Dispersant (aerosol can) and took all the electrical connectors apart under the hood. I cleaned them up and sprayed the connections before reassembling. Never did track down exactly which one was causing the issue, but the problem went away once completed.

Simple to do and the spray does not interfere with electrical conductivity.
Hope that helps.

fireman739

Check all your wires! I had a rodent of some sort get under the hood of my old truck and chewed on my spark plug wires and alternator wires and it did the exact same thing, only when it was damp out too