help please
 

I bought 2002 dodge intrepid 2.7 on the 4th of July 2012 as is ...well when we took off in the car we noticed that if you give it a extra amount of gas that the car would like cut out a little and jerk but after that it drove good just the initial take off,,,so we took it too auto zone and they hooked it to their machine and said it need a crank shaft sensor and a cam shaft sensor so we replaced those and put head gaskets on..those seemed to have fixed that problem,but now after driving the car for a few minutes and you turn it off you have to wait about an hour before it will crank.any idea what could cause this??please help