Ride and Idle

hey all, 2000 grand am gt with 73,150 miles. Lately my car has been experiencing a surging idle on warm start-ups. The car is fine on cold start-ups and is fine until you turn the car off and try to restart a few mins. later. Also, I've been experiencing a knocking sound coming from what i believe the wheels/suspension. I just replaced my front tires and the problem/noise is still present. Any ideas/help is appreciated. thanks.