I have a 2003 Expedition, 209000 miles. In 2015 the engine stalled 9 times over 11 months; 2x waiting at a traffic light, 4x at 70MPH on the interstate, 3x at residential speeds, a couple other random times. Turn the key off restart (sometimes it cranked for 15 seconds before starting) but it always restarted. On the interstate I would just put the tranny in Neutral, turn off the key, and restart and continue like nothing happened. Full fuel tank, half full tank, nearly empty tank - didn't make a difference. Fuel filter was new/replaced. Didn't make a difference. No codes. Essentially an un-diagnosable problem. Until I read the forums.
The first item I checked was the wire and taped it up that someone referenced ("You will find it resting on a silver/aluminum tube (its an AC pipe) Flip the wire over where it is touching this pipe, you will find the wire is rubbed down to the bare metal!!! It is randomly shorting out your engine and you will STALL")
That was not the cause of my problem.
During my Thanksgiving 2015 trip the expedition stalled 9 times and would not restart and had to be towed. ....Fortunately.
I insisted the mechanic go straight to the inside fuse box at the passenger side of the truck. The relay was fried, from dripping / leaking water from the windshield. He also said the heater core seemed like it might have been dripping at one point as well, onto the fuse box. Either way - we replaced the fuse box (put a cover of loose plastic cover over the fuse box). He gave me the old fuse box for inspection. No problems for 50+ days. (as I write this it is now 1/14/16). It is important that I share this tip, as the stalling for no reason part has happened to scores of folks.