Background:

FX4 2006 with roughly 86k miles..had oil changed recently not any other issues since I've had the truck outside of replacing tires, batteries, etc. I was driving my truck yesterday and I was traveling about 50 mph on surface roads when I heard a thud during what seemed like the truck shifting and then I applied my foot to the accelerator and no power. I pulled into a parking lot..shut down the truck..let it sit for 10-to 15 minutes. Started up the truck..took a little to get it going and then it came on. This happened in the past about 6 months ago..it was the same issue driving on a surface road approx 50 mph and then warning lights came on..steering wheel locked up and when I applied my foot to the accelerator nothing happened..pulled into a parking lot..let it sit for a bit. Then started it up and it ran fine..until yesterday, and the same issue happened again this morning! Thoughts on what it could be? Tranny, fuel pump..not sure..would like some insight!

Thank you

 

First thing get the codes read, or purchase a code reader and do it yourself. This is the best place to start.

 

This sounds similiar to a problem I had a few months ago. It started with the truck shutting down while driving about 50 - 60, and my cluster read "engine failsafe mode". It did this several times over a 1-2 month period. I had codes read, and starting attacking them 1 at a time. It continued to happen, then one day the truck wouldn't start 1st thing in the morning. All that happened was the "click" of the solenoid. It would not turn over a bit. I jumped it, and started fine. I had battery tested, and it was good.
The next day, same thing happened. I called my mechanic, and had it towed to him. When it got to the shop, it started right up. He thought it may have been a slightly corroded battery terminal. Turns out, that wasn't the case, as it happened again the next day. This happened for several days - it would not start in the morning, but started fine all day. I figured out that it i tried to start it and waited 20 mins or so, it would start fine.

After several trips back to his shop, he finally figured out that the printed circuit board behind the fuse block under the hood had a broken circuit. Replaced this piece (about $600 for labor, part, towing) and haven't had a problem since. No shutting down while driving, and no starting problems.

Sorry for the long posts, but thought i'd share with ya'll.