tombrush73

2005 F150 STX 4.6

I have been having a really rough idle and stumbling and vibrating while accelerating. Even running on the highway it bucks and vibrate pretty bad. It feels like I am driving over washboard bumps. It's not as noticeable driving through town, but pretty bad on the highway.

I have tried replacing coils and it seemed to help but the problem still remains, any ideas?

screamineagle

What brand of coils? Have you checked the FPDM?

tombrush73

The coils are all stock except one, that's a Napa.

tombrush73

By FPDM do you mean fuel pump delivery module? How do I check that?

Martian

Drop your spare tire and look for a corroded mess mounted to the frame rail.

tombrush73

I thing I found it mounted to a cross piece on the frame that goes from one side to the other. The ends a corroded where the studs come through but not too bad.

screamineagle

Remove it and have a look at the under side where it contacts the frame. You can't diagnose a FPDM without removing it.

tombrush73

Ok thanks a lot. I'll take it off and see.

tombrush73

It has some dirt and grime but nothing major. It has a rectangular small hole on the back that looks like it is supposed to be there. Should I open it up and look inside?

screamineagle

Post a pic. It's a sealed unit and should have no holes in the case. A molded depression yes, but not eroded through to the circuit board.