When my 1995 f150 4.9 standard warms up no matter what gear its in it has a bit of throttle can still change gears and drive i just dont have to use the gas pedal. Its kind of like cruise control it will stay at a certain speed depending on what gear

 

The IAC , Idle air control valve, may be sticking in which case replacing it usually takes care of the problem.

 

I had replaced the iac this morning worked fine for 5 km then back to normal