amigo idle problem

:screwy: ok i have a 94 amigo with the 2.6 l ive noticed my idle speed will sometimes increase depending on engine temp sometimes its lowand sometimes it goes up to about 1500 but it does this weird thing it will start to get a little high on the temp not dangerous just a little higher than normal then the speed will slowly increase and then it will start reving it self it will go from about 2000 t0 500 for about 30 second s and then just stop and idle fine .when it does stop you can actually see the heat gage dive back to normal seems like it does this when i first take her out and drive and when i stop at the first light a few miles down the road this happens any one else heard of this
:banghead: :banghead:

it sounds like when i had problems with my throttle positioning sensor, to find out just unplug it and crank it, if it rus normal then thats it but if it still has the same problem then check other sensors like on the intake or even a vacuum leak.