Kevsharley

Truck ran great and no warning it runs rough. When it started it was just rough idle and cleared up when giving it gas. Now if you give it gas it dies. Cold engine it has a little rough idle, when jumping +B and FP you can rev it up. When it gets hot that trick does not work. The warmer it gets the rougher the idle. Pulled fuel lines before and after filter and fuel is moving through. AFM door shuts when it dies so I think it's good. Any chance it could be engine coolant temperature sensor?

vernvision

Have you tried to pinch the fuel return line that comes from the regulator? If you do after it warms up and it runs better then look for vacuum leaks first off because if its affecting you air flow sensor then it might not be pulling enough air causing it to glitch the computer especially the main pipe...second if you don't have enough fuel pressure could be the wiring to the pump mainly the ground wire...

Its a small diameter and susceptible to first getting dirty at the point its connected to the pump housing and if so it gets hot and cooks the copper and it loses conductivity. If you get that far just replace the wire with a lot heavier and splice it through the oem connector....I have had a lot of trouble with water leaking on my harness resulting in bad grounds everywhere and
it can be very tedious to find the culprit and fix....
The cabs are glued together and it breaks down cracking and letting water in and it takes very little to cause you grief.. All the sensors are easy to check with an voltage ohm meter coolant temp switch is always possible and is easy to check with a pot of hot water thermometer and a ohm meter....looking for resistance when it gets to a certain temp...