transfer case is prolly blown up
My f150 shifts from 2wheel to 4wheel on the fly, but to use 4low you need to be stopped with your transmission in neutral to engage the low range in my transfer case.
Check all the linkage from the transmission.
EVAP Purge Solenoid Stuck Open or Closed
Blowback into a 91 F150 air filter could be caused by a bad PCV valve. Check the valve for it being stuck in the open position.
Is it stuck in rear or front?? Same thing happen to my 89 f150......Front tank was shot...You need to have it looked at
Fuel pump relay is stuck. Replace it.
I would first replace the PCV valve as it may be simply stuck open.
The thermostat may be stuck open.
Trouble code P2111 means: Throttle Actuator Control System - Stuck Open
It could be the fuel relay is stuck.
in ford f150 the u-jounts on the steering shaft get stuck. Use WD40 to help loosen them. Toyota camry's too!