stumpjumper

I have a 2001 F150 5.4 (86K miles) and it developed a bad miss at most all speeds but worse on acceleration. It felt like it was a fuel issue since it was worse on acceleration. Sure enough when I changed the filter it was clogged and when I blew through it backwards some nasty brown gas came out. I replaced & it ran fine for a couple hundred miles. Check engine light which was on went off and I thought all was well. The truck started missing & chugging again though not as bad and the check engine light came back on. I thought the bad gas had clogged the filter again but checked and replaced and still has the symptons. I am beginning to think fel pump. What I do not understand is why it was fine for a while. Any ideas?

Good old Bill

If this thing has the lite on, have the codes read. Am thinking more towards a COP or plug itself.

stumpjumper

That is what I was thinking at first myself. Last time I had a bad COP it was only at certain speeds and the miss was different. It could be more cylinders this time though. Last time it was only #6. The fact that it ran perfect after changing out the filter the first time has me really baffled. There was definitely a filter issue but it good be a combination of fuel & fire.

stumpjumper

How about: fuel pump, 1 COP, and replace all plugs, along with intake gaskets. Coolant leaking out onto spark plugs. I love these high maint. 5.4s. This will definitely be my last one.