I'm looking for a little help; I tried searching but couldn't find anything.
The car is a 91 Z24 with a 3.1 3speed auto.
When the car is in gear and I'm coasting to a stop or light the Rpm's jump around and the car wants to stalls, once stopped the Rpm's settle back to normal after a few seconds. The car was running fine, I replaced the starter last weekend and this problem seemed to happen after that.

Any help in what could be the cause would be appreciated.