96camaroz281988

So my 96 camaro has been acting up. I can start the car drive it across town so meaning an hour or a little more with no problem then park the car for a little bit then come back and start heading back home and that's when it starts to act up. When I'm heading home and hit stop lights or stop signs and I'm at a complete stop the voltage starts bouncing really bad and can hardly stay running at idle and once when u start moving everything is fine. Anybody have any ideas what it could be because I'm stumped lol I just replaced the alternator and I got a new battery sometime in 8/11

n2ceptor

loose connections??
slipping belt??
bad tensioner??
bad alternator or battery??? It would not be the first time a "new" one has gone out..