ive got a 99 dakota with a 3.9 in it,every once in a while it used to cut out once in a while.now its doing it everyday,not all the time though.what it does is like its losing fire and bakefiring and no power and if you hold it on the floor it revs up nice,slip it in neutral and it revs fine.shut the truck off and start it back up and works great for maybe 100 feet or 100 miles,there dont seem to be any pattern to it.my hand held computer is showing code 1391-intermitten loss of crankshaft or cam sensor.anyone got any ideas,i replaced plugs,wires,dist cap,and rotor

 

replace the cam shaft or crank position sensor