My truck starts fine. When in park to warm up after a few months it revs up then low high then low and shuts off when put in gear I have to sometimes give gas quick!! When accelerating it feels like it don’t want to get up go. Other then that it drives fine.
Sounds like a possible vacuum leak or a faulty IAC Valve. The IAC valve or Idle Air Control Valve is a component that can fail and not cause the check engine light to come on in all cases. There may be helpful trouble codes stored if the check engine light is illuminated.
IAC Valve Replacement 2003 Ford F150 4.6L Engine – Video
Labor Time R&R IAC Valve
IAC Valve Location Diagram