87 NA, just charged a/c after installing new pump (first time i have run a/c since purchase). The car idles fine with the a/c on and prior to turning it on, but after driving with a/c on and then turning it off, it bounces from like 800 to 1800. Any idea what is causing this. I found opposite problems in search, but nothing like this.

 

It keeps bouncing, not just once. If that helps.