90 mustang gt with a couple basic bolt ons. Car drove fine then all of a sudden check engine light and battery light came on and it quit. Car would crank over but sounded different than normal (like it was out of time?). Had the towtruck haul it home and put on my handheld code reader. I had a code 15 and 84. I changed the computer and now only have the code 84 (other computer had a chip in it). Car still wont start and still sounds funny. Would only a code 84 cause the car not to start? Any ideas? The car has all new sensors, a new fuelpump and filter, the motor trans and rear were all recently rebuilt.