Accelerator sending unit remedy......maybe.

[Toolmaker51]

Vehicle is 05 F650 with 6 cylinder 5.9L turbo Cummins, 5spd auto-trans, 350k miles, 26,000gvw. Just completed a 2500 mile drive in 4 days, through Missouri, Illinois, Indiana, Ohio, West Virginia, Pennsylvania, and back diverting through Michigan and Iowa.

During latter part, [turning around] began intermittent hesitant throttle response, but not when bumping speed up via cruise control. It also initiated the "Check Engine Service" light. Like many late model vehicles, there's no mechanical connection with intake, just a potentiometer-like sensor linked to throttle plate or similar device. Cruise control doesn't involve pedal, so.....

For whatever reason, the pedal and sensor assembly is unavailable, though pictures and part numbers appear. I'll look for a switch alone if this proves effective at all; googling the switch number only leads to the assembly without mentioning it. Puzzling indeed.
So, I removed assembly to analyze how to introduce contact cleaner to what is basically a drum switch.



Pic 1 depicts drilling through outer wall at about 20°, clear of the cavity bottom, beyond 'standoffs' and through switch proper, and again from opposite diagonal position. Body thickness and logic say internally, there is a commutator not a rotor, and why deep position was chosen, about .12 up from switch face, the cavities not visible when assembled. Very easy test of rotation didn't reveal any interference with shank end of drill, of 1/16" diameter.

Pic 2 Then plugging outer holes with toothpicks, used syringe to fill one cavity while operating the barrel with 90% iso-alcohol, it drained out other side. Part way along, I hosed down the cavities to help reveal whether anything would flush from inside. That was seems inconclusive.

The switch is evaporating alcohol out now under an incandescent lamp.