I have had a reoccuring problem with my 98 Expo 5.4 4x4. First I had a problem with starting the truck. It would turn over but not start. If i turned the key to off then tried again right away it would start on the second try. The second part of the problem was after i drove the truck around it would start up really rough about 400-500 rpm and would want to die out. When you feather the pedal to make the engine smooth out it seemed really bogged down and would take forever to get the rpm up around 2500-4000 and if the gas pedal wasnt touched then the truck would die. Then when you tried to restart it, it would just turn over and over. On some occasions you can floor the pedal a couple of times and it would smooth out and idle around 750-1000. If you would let it sit for many hours then it usually starts up. The truck indicated two trouble codes p171/174 both banks lean. I replaced the 90 elbow at the back of the throttle body, it had a hole in it. And i also replaced the mass air flow sensor as it tested bad as well. Afterwards i cleared the codes and drove the truck around for a few days. The CEL never came back on but i am having the rough start and dying as explain before but if I let it sit it starts back up and no CEL. I can tell that the 90 elbow and MAF made a world of difference in performance and I dont think it could be IAC valve since it doesnt clear up when gas pedal is engaged. Single father of 3 could use all the help possible Thank You. Problem doesnt happen ever time.

 

The symptoms suggest the fuel pump is giving out. Beg, borrow, or rent a fuel pressure tester and connect it to the fuel rail. With the key on and/or with the engine running you should get about 40 PSI. If you don't then you're stuck replacing the pump and it's inside the fuel tank.

 

Would the pressure read low even if the truck is not showing the original symptoms? Or would i have to get the reading when the truck is stalled out?

 

I tested the fuel pressure with the vehicle running and it tested at 20psi. Thank you. I will replace the pump and post back

 

Havent fixed the pump yet. but today i had to run around town. After we went to three or four stores i tried to start the truck again and this time the rpms were 200-300 it cough choked and sputtered for two minutes then finally died out. I tried to start it over and over but it wouldnt do anything but turn over and over. I didnt have the pressure tester with me but I depressed the schrader valve and gas came spewing out but still wouldnt start. After sitting there for an hour the truck started at the low rpms again but this time i was able to floor it a couple times and it cleared up and we got the truck home. Sorry to second guess but do you think it would be the fuel pump even though fuel is present? The pump runs 300 and dont want to get it wrong.

 

Sorry to say but it really sounds like the fuel pump. They are not fun to change but the repair is pretty cheap if you can do it yourself since new pump kits on E-bay only run about $30.