I have a 98 4x4 with 284xxx on body and 90xxxx on 4.6 motor and trans. My power between about 1800 and 2500 rpms seems sluggish, but before and after feel normal power. It feels as though there isnt enough air or fuel, or maybe both. Especially on highway when down shifting and on hills. I am thinking about changing fuel filter and MAF soon cause they haven't been done in a while, any other recommendations? Plugs and wires done about 1 1/2 years ago. Thanks!

 

Definitely change the fuel filter. Check the air filter also. With 90k miles, your engine shouldn't be getting tired. Maybe you need to change your oil to a more high mileage friendly type, and restore some of the lost power you had when the engine was newer. Fuel injectors could be dirty, possible fuel pump getting weak, and on it goes. Was the engine a rebuilt? Time for a compression check maybe. It couldn't hurt.

Have you ran the computer for codes to see if anything isn't working correctly? You may have something set, that may be causing your problem. If you have none, then it's probably more of a tired engine than anything. Also, it could be your transmission might be the weak part and maybe not the motor. It's hard to diagnosis long distance. lol

 

I run valvoline syntech high mileage 5w-30 w/ motorcraft filter. Could I run some techron through the fuel to clean injectors? Engine was not rebuilt, but trans was. There are no codes or CEL, but a compression check may be a good idea. It also just seems to run at higher rpms than it should, like it is searching for air/fuel. Thanks for the reply!

 

Searching for air could be a dirty or damaged AIC. A bad TPS would do that also, but it would tend to possibly buck when you try accelerating or putting a load on the engine. It would also try and search for an idle position, which yours seems to be doing. Good luck.

 

Well, the idle is pretty smooth and there is no hesitation or bucking when accelerating. I will start with fuel filter and MAF and let you know how it goes! Thanks for help and have a great Christmas!