wconnett

Hello there, I have a 2001 F150 with the 5.4, I have been trying to trouble shoot this truck for the last couple of days with no headway. Here's what I got. I start the truck and run it when it is cold and it runs great no hesitation. When the truck warms up there is a slight hesitation in the throttle. It is like it is running out of fuel, but soon as it down shifts it is off like a bat. It seems to be following itself trying to catch up. When it is warm it is smooth until my foot reaches quarter throttle or 1600 rpm. The hesitation sits there till about 2200 rpm or until the truck down shifts.
I have changed the fuel filter, I dont suspect the fuel pump because it screams at the top end. I replaced plugs (motorcraft), cleaned the MAF, checked for vacuum leaks, truck sits about 18 hg at idle. I have replaced 3 cops. I have checked all components of the EGR. I have checked the IAT, TPS, but don't know if I did it correctly I get no codes or no pending codes. The cats are good. I get about 10mpg. I am at a dead end. I would appreciate any help on this. Thanks Bill

rtg143

Try it with the MAF unplugged. If it runs better, you need a new MAF or try cleaning it again.

wconnett

I have tried running the truck with the MAF unplugged and it seems to not make a huge difference. Well it runs about the same. I might next try to pull the o2 sensors and do a bench test. The truck has 200k on the clock, I don't know when they where last replaced. The truck does get very poor mpg as well.

seraphim

Did you get the codes before swapping out the cops? Mine was doing the same thing and I recently changed the 1 that was the problem child.

wconnett

I did get a code on cylinder 8 and replaced that cop. I also replaced two others that did not pass the resistance test. I am going to replace the MAF and see if that works. I will keep ya all posted