Transmission problems?

I have a 1988 jeep cherokee larado with an automatic transmission. the problem that i am having is sometimes it shifts fine and other times it doesn't want to shift. the other problem is that when i stop, after a few seconds the rmp's will drop really low to like 250 then it goes back up to 1000 then after a few seconds it does it again.
i checked the transmission fluid and it is fine.

You have a throttle position sensor (TPS) located on the throttle body. Sounds like that's a good place to start.

http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/15/23/08/0900823d80152308.jsp