It all started out with a misfire. No engine codes coming up ever. I looked under the hood and noticed a missing rubber EGR pressure sensor tube. I took it in and the Ford dealership said that the driver side cat was plugged and the EGR pressure sensor was shorted. ?? So, I had them replace the sensor and missing tube. They also told me it overboosted, which it did. I took it home and it was still misfiring so I replaced the mid pipes and cats with Bassani SS.

The truck ran fine for one run down the highway. Once I arrived at my destination, the truck started stalling. I limped it into the parking lot then had it towed home.

After troubleshooting I found that the fuel pressure was low when idling erratically, around 20-30 PSI and fluctuating all over. One thing that worked temporarily was using starting fluid into the throttle body to keep it at idle for a very short time.

So, now the truck starts, idles erratically, then stalls. The idle RPM goes up to 2000, then near 0, then back up a couple times before stalling. I can hold the throttle up and it will do it for a longer time, but eventually stalls.

I started replacing things. Changed fuel filter first, it needed it. Replaced fuel pressure regulator. Replaced fuel pump assembly.

I've checked many things and had many mechanics look at it, but everyone is befuddled. Most of the replacements were from suggestions.

What could it be?

current mods
cool air intake
single blade throttle body
electric fan
higher amp alternator
accel coils and granatelli coil boots
NGK IX iridium plugs
Bassani mid pipes and high flow cats
everything else replaced is OEM

 

The low fuel pressure makes me think fuel pump. Did you check the pressure before and after the fuel pump replacement? If so, was there any change? Are there any flexible lines that could have been pinched during the pump replacement? It is uncommon but not unheard of for the new pump to be faulty. But, I know it's not a fun part to just replace again on a guess.
Also, I don't mean to insult, but is there any way the fuel filter could have been installed backwards?

 

99% chance going to be the plastic Y in the tank cracked

 

checked pressure before and after, same symptoms. fuel filter is correct way. All lines were inspected and look perfect.

I did not look at the plastic Y, will have to drop tank and check that.

 

they are prone to crack or maybe you had a fuel line split inside the tank


what is the fuel pump resistor doing??

 

checked everything, all was good. now it's at the shop to get fixed by someone else.

 

i have almost the same problem, i took my lightning to work one morning and not even 1/4 mile from home it starts surging, once i stop the truck it stalls... get it home look through my snap on scaner.... no codes, i troubleshoot it and it says if the map sensor is below 153 hertz suspect maf or map, i replace the map and still starts and stalls, maf is reading properly, i cleaned the maf, just put twin walbro 255lph pumps in. now for me the cracked "y" makes sense. for u there are 2 relays next to your fuse box under the hood these change voltage for fuel pressue to be high at wot or low under normal driving. i would think to check this

i just seen the post is from '04 but its good to know some more details

 

good choice tarajerame, it was the fuel pump resistor.

i used good relays also, no change

 

https://www.f150online.com/forums/li...its-alive.html

 

cool, same problem and it's fixed now.

 

I am having what appears to be the same issue. Drive for a while, when engine gets up to normal opp temp, starts to stall out. I have replaced the fuel pump twice with an aftermarket (Napa). Dealer said again today that it is still fuel pump. I read through the thread and say the part about the plastic Y. I am not sure what/where that is but would like to check it out. Any direction?

 

it's right there where the fuel pumps are (connects the two pumps to the single fuel line):

 

Thanks I'll give that a try!