I have a 98 f150 with the 4.6 I have replaced the throttle position sensor 4 times it don't fix the problem what else could it be?

 

Hang on let me use my magical powers to see what your trucks symptoms are.

 

Stalling hesitation lack of power very bad gas mileage

 

You got any codes or check engine light. May be bad cat or o2 sensor

 

I don't have any cats or o2s and yes PO123 code

 

When you say TPS, are you talking about the throttle position sensor? If yes, a faulty TPS will not cause stalling, hesitation, lack of power or bad gas mileage. It will prevent the transmission from upshifting at the proper time as speed is increased.

 

Yes that's what I'm talking about. And yes it does cause late shifting along with the other I named.