cough/miss/

I have a 2002 stratus and everytime the car get warm ,it gets this cough (only when it gets warm). but if i turn on the air conditioner ,it almost goes away( its a lot less noticible).
also after driving it you can shut the motor off, and i have no pressure on my upper radiator hose and i can open my rad cap and also have no pressure (with the motor not running).
I CANT CALL IT (please help i you can)