2001 F-150 8 cyl trident engine less than 100,000 miles and kept up regularly by ford dealership. While coming down an offramp from a freeway, the engine locked up. There was no engine trouble light. Water temp and oil pressure normal. We pulled off to the side, coasting in neutral (automatic trans). Tried starting, but the engine would turn around a half-inch, then bounce back to where it was. Tried a jump start, but the same thing. Had truck towed to ford dealership, where it sat for three days before it was looked at. For them, it started right up. They hooked it up to their computer, but it showed no problems. They then drove it for ten miles with no problems, and it was released back to us.

Has anybody heard of this happening before, and if so, does anybody know what could cause it?\

Ford dealer inspection report:
"At the time of entry, vehicle starts and runs normally. No codes in PCM and no relates TSB/SSM in oasis. Test drove while monitoring fuel pressure and PCM data. No concerns present.Fuel pressure and fuel trims and other related data show no concerns. No power/ground concerns found. System working as designed at this time.

 

One of my questions would be, did it sound normal when attempting to restart?
It does sound like it lost all power to start and keep running. Insufficient power to the ign syst could cause it to shut down, but since the starter would not do anything ,I would be checking all the electrical connections to the fuse panel and from the battery to the rest of the vehicle, grounds included.

Has the windshield ever been replaced in your vehicle?
They did have some problems with windshields leaking during those years, and causing some unexplainable problems at the fuse panel.
Look for rust around the parking brake assy and fuse panel, that could confirm a moisture problem.

 

This was a mechanical lockup. Parking brake was okay as was the transmission, as we could easily push the truck. I suspect an injector leaked flooded a cylinder and locked it up. The fact the truck was at idle as we left the freeway kept it from breaking the engine. I just went out and smelled the oil, but couldn't tell if excess fuel leaked down, but I suspect that's what happened, and why the truck started right away after sitting for three days. We're having the oil changed tomorrow, just in case.

 

Curious to know what you find, thanks for keeping us informed.