I am working on an 01 navigator with the same issue…i will look into this as well because he had the engine rebuilt recently…thats when the p0171 code started.
Okay so the final verdict is in. The PCV elbow that I had jerry rigged along time ago finally died. So I went to the junkyard and got one that looked fairly new and bingo my LTFT dropped from 19.5 down to 0. And my STFT
Thanks for giving us the update. I’m impressed, again, that Scannerdanner came through with a solution unique to this vehicle. I guess a smoke machine would have helped find it as well.
This is typical of most Ford vehicles of this era. I’ve seen bad PCV elbows on escorts, focus’ zetec and SPI engines, escapes with the v6. Atleast its an easy fix. Glad you got it sorted out.