any suggestions on what it can be why it goes into engine failsafe mode? its a 2004 f150 5.4 with 51300 miles
I have a custom tune with 93 octane
4.10 gears
posi unit
80mm bbk throttle body
k&n intake

 

I had that happen to me too, just last week. You might first want to pull the codes.

In my case it was P2111 / Throttle Actuator Control System - Stuck Open and P2104 / Throttle Actuator Control System - Forced Idle. Based on that and the helpful info I found here it was suggested to clean the throttle body and MAF. I did that last weekend and no problems since. Actually getting a little better MPG now. I'm sure there could be other factors at play though.

 

When does it go into limp mode? Something running hot? Tried going back to factory tune?

 

this is the second time it does that but this time it turned off completely, but I'll clean those things and see if that helps

 

it did go limp mode, temperature is right and I'll see if I can get the tune checked

 

Check codes, I'd go back to the tuner.

 

To rule out the tune, clear the code(s), then re-install the stock tune and run the truck that way for a few days. If it runs fine, re-install your tune. If the code and symptoms return, you know its related to the tune.