I need some help. The truck seems to run fine when cold and under 3000 RPM with less than 3/4 throttle. During the first few miles, I can floor the accelerator pedal and the truck accelerates normal. After awhile, the engine justs seems to stumble, cut off after about 3000 RPM and the truck will not accelerate. No codes come up. Fuel pressure was around 26 to 30 psi in park, at idle and 3000 RPM.
I changed the fuel filter, air filter, fuel pressure regulator and cleaned MAF sensor.
I'm planning on changing the fuel pump. Is it really bad since it runs good when cold? I also, was told it could be the catalytic converter. Any suggestions?
Thanks

 

So why change the pump?

 

I wonder if this is a problem with the EGR valve or vacuum lines to it?

 

EGR shouldn't come into the equation at WOT.

The question is: What's the fuel pressure when it's doing this? Yes, you need a gauge with a very long hose that you can run into the cab while driving it. Or, if you power-brake it and it does it, check it with the hood up and the gauge visible from inside, or by a helper.

Also, pull the vacuum line to the regulator while it's idling and see what the fuel pressure is. It should jump to 38-40 or so.

It's possible you're not building fuel pressure for that WOT run.

If the WOT fuel pressure is still good (38-40 it should be), the fuel pump is NOT the problem...

 

I warm the engine at idle for 5 minutes. Fuel pressure was 30 psi and would go to 32 psi with throttle.

I then went for a drive. Fuel pressure increased to 38 psi while accelerating with light throttle(normal driving). With WOT in would increase to 40 psi. Truck is driving fine.

After a few miles this is were the problem occurs. At idle fuel pressure is 30 psi. With light throttle the fuel pressure begins to drop to about 20 psi. At WOT it would drop to 15 psi.

 

You already replaced the fuel pressure regulator and fuel filter, right?

Definitely sounds like the fuel pump can't keep up with the flow. That's where I'd go next.

 

I changed those items.

Why does it happen after the truck is driven for a few miles? Could it be the catalytic? There is a rattle when I tap it.

I did vacuum check at idle 22 hg, 1500 rpm 23 hg, 2500 rpm hg.

Thanks

 

It sounds like it is going into limp mode, telling the it to drop fuel pressure. Coolant temp sensor ok?

Not sure if that is it. Just throwing some ideas that may trigger someone else's mind to what it may be.

 

2 weeks ago I was working on a 2005 f150 3v. It had the same problem .

Anything over 1/2 throttle and over 3krpm it would break up . Like a lean misfire. Fuel pressure was perfect tho. It was the coil packs and plugs were shot at 60k miles. $500 later 8 coil packs and plugs and it runs like new.

You check fuel pressure again after the new pump install?

 

Other than mine pinged,,, this sounds exactly like my problem.
I did all the things you did and more.
Mine was clogged cat @ 30,000 miles.
Thread here:
https://www.ford-trucks.com/forums/9...-2004-v10.html

hth
good luck.
cheers
jimmy p

 

I changed the fuel pump and that solved the problem.
Thanks for all your help.

 

2004 F250 V-10 auto XL w/4:33 gears

I hate throghing parts at a rig. I want to know what is broken and why before I fix it.
Mine does the same thing, except if I turn the truck off and back on it runs fine for about 5 minutes then it is the same thing all over again. Runs fine cold. My cutoff rpm is 2000 before it stumbles. I use the truck for a plow which makes it a lot of fun.

 

Have codes checked. Check fuel pressure while driving.

 

Gents;
Came across this thread just after I posted an eerily similar one a few minutes back:
https://www.ford-trucks.com/forums/1...underload.html

Any chance you could have a look and let me know if the fuel pump is suspect? I have not yet done the fuel pressure testing in depth, but that was my next plan.

Any comment on the quick engine off/restart? This temporarily "fixes" my problem, but it does return quickly.

Regards,
SteveCo in St. John's

 

Your problem sounds the same as motogp310. His fuel pump was the problem, sounds like your is too. Your pump problems could have been triggered or even caused by running out of gas a little while ago.