I have a 2000 f150 4x4 that sat for about 6 months. while I rebuilt transmission. now if i reset computer and start it to let idle straighten out it holds a 2000 rpm once i drive a few miles its holds a steady 1000 rpm. any ideas? I hate throwing money at it till it gets fixed.

TIA

 

I'd clean out the throttle body (IAC and EGR ports included) and change the fuel filter for good measure. Sitting for a while can cause stuff to stick.