Are you getting a trouble code? If so, what is it?
Fail safe or "limp home mode" is usually because of a significant sensor failure (I.E. MAF, low fuel pressure, etc.). There should be a code stored.
"Never argue with an idiot; they'll only drag you down to their level, then beat you with experience"
2007 F150 STX Supercab (4.6 2V V8), Edge tuner, factory navigation, Mark VIII electric fan conversion with flex-o-lite controller.