2000 Durango rough idle question

First thing that comes to mind is a defective engine temp sensor. Do these symptoms go away after you drive it a bit?

I have a 2000 Durango with the 4.7 and am having a problem with the idle also. Basically, when idling with the AC off the RPMS bounce between 500 and 1000. When it gets to 500 or below, it seems to sputter like it is going to die but then catches itself and revs back up. When sitting at a stop light and idling, I often catch myself inching forward if I do not keep a heavy foot on the brake. With the AC on, it still bounces, but between around 700 and 1200 and it does not sputter like it does when it gets to sub 500. My problem does not go away after driving for awhile however some times it seems fine but most of the time I am afraid it is going to die on me. Any suggestions? I would like to get an idea of what it COULD be before I pay to have it worked on.

Unfortunately, no, the problem does not go away. I also see the problem driving along at a steady speed. When driving it's not a drastic increase and decrease, but never-the-less the RPM's are not stable like they used to be. This morning it ran fine, but the temperature was in the mid-30's...

Is there an ambient temperature sensor on the vehicle?

thanks