Hello all...new to this forum and a little desparate! I have a 2001 Expedition Eddie Bauer edition 5.4L Triton with 138k. It started misfiring badly the other day, so a mechanic friend replaced plugs, coil packs air filter and pvc valve. Two of the plugs on the drivers side were covered in oil. The rest all showed normal wear. Ran awesome all day yesterday and this morning. Started it up after work today and it is misfiring again. Mechanic says maybe its the fuel filter, but why would it run great yesterday then terrible today? If the plugs are fouled again, what could be causing it so quickly? Could one of them have worked itself loose? Any suggestions would be appreciated. I really need this vehicle! Thanks.

 

The COP's crap out when something leaks down into the hole where the spark plug is.

A lot of fellas I know also see the spark plugs take a **** faster when the COP has been all fouled up. Could be fiction and fantasy, but I know that mine took a dumperoo when my coils went bad. Maybe they were on their way out, but that must have tipped it.

I would pull the COP's yourself or have your mechanic pull them, if they look physically good, then try switching the suspected bad ones, with one that is good.

If he didn't use Motorcraft plugs, that can be an issue too. I have never had a problem with cheaper plugs, but from what I hear they are getting worse and worse.