Ok guys Here we go
I have a 1999 Ford F350 Powerstroke with manual trans 4x4

I had a problem with the T.P.S. in the floor conected to the throttle pedal
It would not accelerate I replaced the sensor and it cured part of the problem Now when I put the transder case into 4 high or 4 low I can't accelerate Put it back into 2wd and its fine
I have had it to three seperate dealers and they can find absolutely nothing

Is there another controling sensor Or some other problem

Please Help
Thanks John  

Figured it out after many exausting hours    

The fuse box under the steering wheel  Slot 19 fuse  A wire had came out of socket in the back of the fuse box    


It really sucked    So just to let you know