I have a 92 F150 5.0 5speed that I was told the motor was replaced with a 90 model.When I shift the motor revs up with the clutch in and sometimes you can hold the motor back with your foot on the brake but when you push in the clutch it revs up again.Sometimes it will stay up for 10-15 seconds before slowing down.>Is this caused from the year diff. or possible automatic computer.Sometimes it works fine but not often and it dont matter if cold or at operating temp.>Not much on fuel inj. and computers can anyone help?

 

it most likely the computer. was the truck at any time a automatic. if it was you have to go to a juck yard and find a manual computer out of a ford 5 speed truck.