I had my Nissan Sentra as a pre owned vehicle for 2 years and it was doing good. suddenly the battery went dead because of the alternator that was not charging the battery that well. suddenly when I got it all fixed the engine stopped after running it for 20 mins. Mechanic advised me to change the ignition coil and still the same problem occurs. What else do I need to do or have some parts checked. This is my only car and I drive it to work everyday.