Running Rough

[STEWART]

I have a 99 F250 crew cab 4x4 that has never let me down. lately it has been running rough and losing MPG. Here is the scenerio:

Its been cold in the morning 20+degress, truck spends about 15-20 min. warming up before I leave for work. Runs a little rough but only noticable when I am stopped. Get to work - 10 wonderful hours go by, start my truck, around 5pm, temps up to 40degrees, let it warm up so the heater is working (10 min). Put it in gear, back up, stop and she start to try and stall on me. I changed my filter, what else may be my problem.

 

[DaveBen]

What filter did you change?

Dave

 

[STEWART]

I replaced the fuel filter. Last nigh changed the Oil and filter, bled off the fuel/water separator and put in some additive in the tank to get rid of any water that may be in the tank. In the morning it is a continuous drive to work so I don't notice any rough running. The problem occurs at lunch or when I leave, it is stop and go around town when she starts to run rough. even lettering the engine warm up doesn't seem to help.

 

[Tail_Gunner]

Do you have a fuel pressure gauge? It's possible your fuel pump is getting weak. A weak fuel pump may put out better pressure when cold and start to get weaker as it gets warmer. A good factory fuel pump and pressure regulator will put out in the neighborhood of 55psi. Many folks will shim the fuel pressure regulator to up the pressure to about 70psi.

Just a guess.

 

[Wingdog]

Check your in tank filters. They with be in the pick-up "mixing chamber" if they are plugged then you will get no fuel to the pump even.

 

[action4478]

I have a 99 F250 crew cab 4x4 that has never let me down. lately it has been running rough and losing MPG. Here is the scenerio:

Its been cold in the morning 20+degress, truck spends about 15-20 min. warming up before I leave for work. Runs a little rough but only noticable when I am stopped. Get to work - 10 wonderful hours go by, start my truck, around 5pm, temps up to 40degrees, let it warm up so the heater is working (10 min). Put it in gear, back up, stop and she start to try and stall on me. I changed my filter, what else may be my problem.

Maybe this will help.....Rough idle, especially hot:
Could be caused by anti-foaming agent depletion, incorrect oil, or leak at the oil pump pickup tube.
Get the engine and oil hot and run up to 3300 RPM for three minutes. If the ICP reading goes above 1600 within the first thirty seconds of testing there could be a cracked pickup tube or missing seal. The pick-up tube can be checked by adding two quarts of oil to the crankcase and raising the rear of the vehicle approximately ten inches. If the ICP readings at 3300 RPM drop, then the pick-up tube is cracked or leaking.
If at the end of the three minute high RPM test the ICP readings are above 1400 for Federal or 1250 for California and Econoline or 1500 on 99.5, the anti-foaming agents are depleted from the oil or the wrong oil is being used. ....Rick....