I have 05 F-150 5.4L with 40,000 miles. When going up hill or trying to pass it goes flat and will actually get slower. Took it to my mechanic and he changed the fuel filter. This helped but still a problem especially when motor has been driven several hours and it is hot and when gas tank is less than half. Took back to mechanic and he checked the new filter. He checked on the computer and nothing comes up. I also took back to dealer and they also could not pinpoint a problem other than maybe trash in fuel line. They wanted to change out fuel pump and clean out fuel system for 850 dollars. Has anyone else came across this problem and what did you do to fix. I will pay to have it fixed but would like to know what is the real problem. Also when the motor is not hot such as first thing in morning this does not happen and motor runs perfect. Does not sound like trash in fuel system to me. Thanks

 

One possibility is the cats or a muffler has collasped blocking exhaust flow.
One way to check is drill a small hole in the head pipe and weld or thread in/ on a threaded adpter.
Use a metal tube about a foot long to thread into the hole then connect to a vacuum gage so the heat dosn't get to the gage.
The gage should be capable of reading a small amount of pressure off zero in the other direction of about 6 psi or more.
The con ection needs to be tight non leaking.
On a road test, it you see more than about 1 or 2 psi under hard accelleration, the exhaust has restriction at some point.
When done testing use a standard plug in the hole.
Just need to select the parts in 1/8 or 1/4" pipe size to make this a useful testing port..
OR... take the exhaust apart and road test.

 

I have this problem too espicaly when it downshifts to pass somebody it will hesitate bad. If I remember right when I had my Edge it didnt do this. I also though that there was a pcm reflash to solve this problem? Maybe someone that knows for sure will chime in.

 

If you unplug the battery for a while, 30 minutes or so, the truck will have to relearn the adaptive strategy and then the engine will become more responsive, or at least that's what I remember reading here somewhere.

 

Thanks for the replies. I will try the battery disconnect first and see if any improvement in performance.

 

Did you guys ever use a fuel system/injector cleaner ?

 

Addition to my post. If you feel like itull the cops & check the boots for arcing. If you have it,replace the boots & use a healthy amount of dielectric grease to prevent tracking/moisture problems.

 

yes I have used fuel/injector cleaner probably 3 times. I used the Gumout brand. I did not notice any change.

 

I would run a can of SeaFoam directly into the intake from either the PCV or brake booster line.

 

Here is an update: I ran a bottle of seafoam in the gas tank and I think the problem is fixed at least for the time being. This weekend I drove 500 miles on the interstate and no problems. I could pass and drive at speed with normal power. I guess I will run a bottle every 2 or 3 thousand miles to prevent this in the future. Anybody have any thoughts about this?

 

You might want to try the fuel system cleaner kit to clean out the injectors. Consists of a can of cleaner/gas,a hose with a valve to connect to fuel rail service port and a adapter for the can.
If you do that,I would use a fuel system cleaner after each oil change.

 

good to see you got her running good again. ive found when a cat is collapsed or blown apart inside the engine overheats because of all that exhaust has nowhere to go.

 

Mine is doing the same, what is a bottle of seafoam? wher may i buy it one?

Art

 

Seafoam is one of the better engine cleaners out there. Available at most auto stores, comes in a white can. It says you can add it to the gas to run though, but most people get better results disconnecting the brake booster vacuum hose, and then just sticking the hose into the can. The engine's vacuum sucks it through the TB and all the other junk.