paulsing idle problem

Now that it is summer i use me AC ever once in a while. after using the ac and turning off the car when i start it up, it starts out like normal but then it will drop below its normal idleing position and then over the idleing position. A couple of times it even shut off. anyone have any idea what is going on.

befor shuting off the car i turn all nobs to off position.
1994 coupe, fresh paint, rebuilt motor and new tranny.:gringreen