So, I have a 2004 f-150 4.6 v8, 92,000 miles, had trouble with low idle and had stalled on me 3x's. Cleaned MAF with no change,replaced fuel filter (was last changed at 45,000) no change.cleaned throttle bottle while running and things got worse. Noticed throttle body was oily/sooty. Removed throttle body(only 4 bolts and two plugs to undo) and cleaned it with contact cleaner and toothbrush(not my wifes electric one)till everything was shiny.Replaced all, I do not remember truck ever running so well. My theory is this. The fly by wire throttle body motor is'nt strong enough to overcome any dirt/oil/sludge. If it was cable your throttle pedal would just be harder to press. Fixed this for $20 in sprays and a filter. Good luck.

 

Great tip! Thanks for posting.