I've been noticing that when my truck warms up and has been run for a while that the idle seems reallllllly shakey when I let off the accelerator pedal. I can goose the pedal a bit and everything smooths out again until I run her up to speed. Once I let of the go pedal it shakes your teeth out until you tap it again. It doesn't do it all the time and never (so far) when it's cold. Any suggestions or ideas from the FTE Braintrust??

 

Rough idle, especially hot:
Could be caused by anti-foaming agent depletion, incorrect oil, or leak at the oil pump pickup tube.
Get the engine and oil hot and run up to 3300 RPM for three minutes. If the ICP reading goes above 1600 within the first thirty seconds of testing there could be a cracked pickup tube or missing seal. The pick-up tube can be checked by adding two quarts of oil to the crankcase and raising the rear of the vehicle approximately ten inches. If the ICP readings at 3300 RPM drop, then the pick-up tube is cracked or leaking.
If at the end of the three minute high RPM test the ICP readings are above 1400 for Federal or 1250 for California and Econoline or 1500 on 99.5, the anti-foaming agents are depleted from the oil or the wrong oil is being used.