Fuel problem, I think.

[archsu]

my 1999 expedition was running great until it started to stall and lose power one day and then it died. I changed the fuel filter and fuel pump and now it idles but when I step on the gas it hesitates and will die if I do not let off the gas. If I gently step on the gas pedal I can get it up to about 1500 rpm's and then it starts to sputter and will start to stall. If I let off the gas then it will go back to idle and be fine. Any ideas would be greatly appreciated.

Thanks,

 

[rex450se]

my 1999 expedition was running great until it started to stall and lose power one day and then it died. I changed the fuel filter and fuel pump and now it idles but when I step on the gas it hesitates and will die if I do not let off the gas. If I gently step on the gas pedal I can get it up to about 1500 rpm's and then it starts to sputter and will start to stall. If I let off the gas then it will go back to idle and be fine. Any ideas would be greatly appreciated.

Thanks,

Not the exact same symptoms that were on my wife's '98 but similar. Her's would start but if you didn't have your foot on the pedal it would immediately die. It ended up being the Idle Air Control valve. Less than $50 and about 5 minutes and it was fixed and has been running smooth ever since. Maybe worth looking at.

Victor

This was the one for my wife's '98 with the 5.4L. 2 bolts and a plug, really simple. Even came with a new gasket.
http://shop.advanceautoparts.com/we...r-control-valve-bwd_18481630-p?searchTerm=iac

 

[Thermo]

archsu, you will need to measure the fuel rail pressure. If you connect the pressure gauge (connection is on the passenger side, will look like a tire valve stem right on top of the motor), then turn the key to the RUN position (do not start the engine), the pressure gauge should read 40-50 psi (closer to 50). If it doesn't, then you have a problem with the fuel pump more than likely (could be the fuel pressure regulator though too). Now, start the motor and you should see it drop to 30-40 psi (running closer to 40). If less than 30 or down near 30, replace the fuel pump.

Some OBD scanners have a connection to the fuel rail pressure sensor and you can see the pressure that way. But, you need a higher end one, not the cheapo ones you find at WalMart.