GMC Envoy stalls when air conditioner is on and idling

2004 Envoy only dies when A/C is on and idling if it is in park or neutral no problem. Also will not crank after fueling once started will continue to turn over till refueling again. And service engine soon light is on stating needs new gas cap. Replaced gas cap and the purge valve. Worked great after replacing valve. Two weeks later I started same issue with fueling and stalling.