ok i have a 98 Ranger 4.0 4x4 just recently i been loseing power and start to bog down and it will stall out on me (automatic) lucky it has only stalled out in areas where i can just coast it off the road and get it to start again and i have to rev it up quite a bit in park or neutral before i can take off or it will just bog down when i try to move in drive i've already changed the plugs and wires and had new converter and muffler put on it (since they had holes in them) and it still is loseing power i'm in the process of trying to figure out how to get the fuel filter off to replace it but are there other reasons that it would be bogging down other than fuel filter and plugs and wires?

 

Try checking the air filter, it won't hurt. Its very likely to be the fuel filter. If the fuel filter is too bad, you might want to drop the tank and clean it out. Is this only happening when the tank is lower, or at all fuel levels?

 

air filter is clean its brand new but it happens at all fuel level like now its at maybe half a tank and it got worse it staled out and every time i restarted it it would sit there and just putt a little and shut off again i made it home maybe half way home it just started running normal until i go to start it again

 

You might want to run a fuel pressure test, sounds like the engine isn't getting enough fuel. Try the fuel filter first and then I would suggest pulling the bed and checking the pump itself. But do the fuel pressure test first!

 

i found the problem its not fuel problem its the mass air flow i just replaced it and it still runs like crap but when i unplug it then it will run great but shift hard of course i don't know what else down around the mass air flow that would make it run like this

 

Try to return the one you bought. If you got it new, it should be covered under warranty. If it runs better unplugged, it means that the sensor isn't working properly so the computer runs according to the readings it gets. If the there are no readings, it reverts back to a factory set safe run mode. It will get bad mpg like that, but at least its running. The MAF along with the O2 sensors just let the computer trim the fuel/air ratio for a more economical mix

 

Sounds like the ECU (engine control unit) may running in a simple "limp mode". It will do this when one major sensor is out of tolerance, or fuel pressure is not correct. This allows you to drive the vehicle, albeit at a simple, slow pace. Or, you can have an ignition break down. A coil can break down under load, but idle just fine.

Unplugging the mass airflow sensor to get it to run better leads me to think its still fuel related. With the MAF unplugged, the ECU is not using it to detect the amount of air the engine is seeing or using, thus adjusting the fuel pressure to the fuel rails which feed the fuel injectors.

You need to check the fuel pressure at the fuel injector/fuel rails. There should be a valve on the rail that allows a fuel pressure testing guage to be connected to. This test lets you know that yes, you have good fuel pressure, or no, you don't. If you don't, then the fuel filter or the electric fuel pump (in the gas tank) are suspect. I don't believe these engines use a fuel pressure regulator which is used to route fuel back to the tank from the fuel rails. Instead, the pump is cycled on/off, based on sensor input to the ECU. Ford switched to this type of system in many of their vehicles in the late 1990's to early 2000 years, to help prevent vapor lock in the fuel lines.

If its the fuel pump, some find it easier to remove the 6 bolts, the fuel filler tube, and the wiring harness to the bed and remove it to get at the gas tank top, where the plate and its circular hold down are easily accessable.