Ok so I recently bought a 2001 Ford Mustang V6 (automatic) from its original owner, every thing is good except after I hit a 65+ mph or when I accelerate really fast, once I come to stop as my car begins to slow down it just turn off. And right before it turns off it feels almost as if the car shakes. What is the problem???

 

Now when you say 65+ mph; do you mean you hit 70 and the car dies even with you still on the throttle? Or is it; you hit 70, let off the throttle, and it dies?