Hi dave,

Like, TXBill said, turning the idle knob counter clockwise will increase the rpm's and you will be able to find a smooth idle, esp, in colder weather.

If by chance the adjustment knob is hard to move, you can remedy by removing it from the dash and working some WD40 into the cable.
Also you can made more idle speed adustments under the hood. (follow the cable)it is self explan.
If it is cold out I turn the idle up some and let it warm up then I reduce when she reaches normal operating temps.
good luck