I have 2004 F-150 Lariat with 3v 5.4L auto and 83,000miles on it. Overall she runs great. Had engine fail safe mode come on when truck sat for 4 hours after getting to work. Fail safe went off after I stopped and restarted engine. Fail safe has not come on again. A few days after that check engine light came on while driving down highway at 65 mph. Truck was running nice and smooth when check engine came on, no loss of power nothin. Check engine lighr was on for a day and a half then went off. The only issue in terms of how engine runs is that at random it will quit with no sputter no signs when slowing down on off ramps or when driving in parking lots. It starts right back up with no issues at all. It will do this at random and may not quit for days in a row. Again engine runs perfect in general.
Does anyone have any ideas as to what it could be or what I should look for. Plan to take truck to shop but need to wait cause funds are tight until next month.

 

It sounds as if a sensor that triggers the fail safe mode has a malfunction!...........only problem is finding the right one!........

 

I wonder if the throttle position sensor is acting up? Mine did it once and threw a couple codes pointing to that. Went away and hasn't happended again in 5k(knock on wood)

 

Get your codes read and report what they find back on this thread. Someone will help you then. Otherwise its all guessing.