Hello, I have a 1999 ford f250 superduty 4door 4x4 with a 5.4 with 335138 miles that has me stumped. I will begin where the problem started. I took gas out of my boat and put it in my truck everything was fine. Then after 40 miles of driving it began to run really bad. I would press on the gas and it would bog down and sounded like it was back firing. When I shut it off for 10 sec it would would run fine for a few mins. So I emptied the tank and changed the fuel filter ad put drygas in it thinking it may have some water in their but it didn't help. So I took the plugs out and 5 of where shot. I replaced all the plugs an it still didn't help. So I order 8 COP installed them took out all the injectors and inspected those (seem fine) then truck ran great for about 15 mins then back to the same problem. I went and bought the Tps sensor and that did not help. I am not sure what the next step I should take. Also no check engine is coming on.
Thanks

 

I am thinking there was an issue with the gas you took from your boat. it seems you have done a lot without success.

 

Throughout all this, is there no CEL or have you not checked for codes?

 

335138 miles!

I'm impressed!

Check the fuel pressure. I suspect something in the fuel system is almost plugged up. That may explain why after sitting it runs better for a short time. Maybe some fuel is seeping through the restriction. Just wild guessing here.

 

The sock strainer in the tank could be plugged up, the injectors themselves may be plugged. Sounds like it's time for a complete fuel system cleaning.