I have a 99 E250 with a 5.4 260k miles.
A few days ago while running down the highway, the engine suddenly lost power. I could still move, but if I touched the gas more than just a touch, it would sputter. My first thought was to change the fuel filter. After doing so, it seemed to be better for a few miles, then it began doing it again. I can just barely touch the gas to slowly gain momentum, but a hill would kill my speed back down. Idles fine, but no power. Sometimes the problem will clear up a little for a few miles, but still doesn't feel right. Then bam right back to no power.
So I got a fuel pressure tester hooked up. With engine off, the needle barely moves. As I cycle the key on/off, the needle will slowly rise each time, but will max out at around 22 psi. With engine running the pressure stays at 22 also.
I changed the MAF and a couple of vac lines and can find no other obvious leaks. I'm hesitant to change fuel pump, since I've never had one act like this. Any suggestions?
Perhaps the FPR?

 

If I'm not mistaken the FPR is forward of your test port--if so then at this point your issue is either from the fuel pump itself or (less likely) the fuel filter.

Fuel pressure should be about 35 PSI IIRC.

 

Just changed the FPR. Not it.

Still only getting 22-24 psi with the gauge. Drops to about 15 when I give it gas. Moving on to the fuel pump, I guess. I've never had a pump do this. Usually they just stop. Period.
But it's not like I have a ton of experience, though. Fingers crossed. Thanks for the reply.

 

Turns out it was either the fuel pump, or the dirty filter sock. I changed both, and the van now runs better than it has in a while.