what can cause the motor to go from normal speed the fall flat on its face even from 70 mph down to 20 if that an not pick back up for a while

 

Possibly a fuel supply problem. Cannot condemn the fuel pump itself without confirming all power and grounds are good and functioning. Also , different models have different fuel control set ups. Has the fuel filter been changed lately?

 

i have changed line ruber and metal fuel lines pump filter regulator vent ports on tank . plugs coils getting ready to do the cam sensor in the morning .

 

Cam sensor might prevent it from starting, but I don't at this time believe it would cause loss of power, yet a questionable crank sensor might. Does the RPM tach show a sudden loss of RPM when this happens?

 

yes it loses power down to 1 rpm but if it is a small event it goes right back up if it is a big event it takes a while or it dies a few times it just depends on wht the truck wants i changed the chrank sensor last year .

 

Ouch !
Fords don't usually have too many problems with crank sensors, but There may be a relationship here.
Can we ask why you needed ro replace it?
Also , might be a good idea to take another look at it and the mounting and wiring.
Did you you get it from Ford?

 

it went bad truck wouldnt start a year ago and i changed starter batt pluggs coils and it was a sensor it was a factory direct order part . did the same this time as well cam sensor amd chrank bioth changed today hope it fixes the problem