1995 Chevy Cavalier

Engine problem
1995 Chevy Cavalier Engine Size unknown Wheel Drive Type unknown Automatic 172500 miles

I have a couple of issues with my car. First, when I am driving down the interstate my car does just fine. But when I am slowing down to get off the interstate or come to a stop in slow traffic my car cuts off. Some times it takes a while to start it back again. What could this be? Second, we replaced the throttle position sensor due to our fan not running. But if you crank the car and unplug the sensor and plug it in again the fan starts running. But if you cut it off and back on again it stays off. During the summer months we noticed the fan ran while the air conditioning was on but now it does not. Help please.

Thanks.