I have a 2008 F250 with the 5.4...and I'm stumped. I've searched/read many posts on truck forums, but wanted to hear from the geniuses here as well, since I've always received good advice and direction. My truck had developed a slight hesitation during hard acceleration...so I changed fuel filter, and it was a bit dirty. Drive all town mostly, and it runs great. I get out on highway... seems to run good, set the cruise and as soon as I start to climb a hill it started bucking and carrying on till it dropped a gear, then it smoothed out. I decided, might as well throw on 8 new C.O.P. I get all of those on, and fire it up and it sounds better, drive it hard and it stumbles really bad...backfiring and acting all unhappy. I check them all, they are tight and all good. Under normal driving, it's fine. Drove to work this morning... ran ok, not much stumbling but not perfect. On the way home...runs horrible. Through all of this, no CEL. I hook up my X3 and it reads nothing as well. This is driving me crazy, as there are no codes...and the severity of it is inconsistent as well. I'm wondering if it's possibly the fuel pump relay switch, or fuel pump....or something else I may be missing here.
Any possible help/ideas from you guys as always, is greatly appreciated.
Any possible help/ideas from you guys as always, is greatly appreciated.