Your Mechanic has over looked the Crankshaft position sensor. This sensor, when failing will usually fail when hot. Without this sensor input to the PCM, your ASD relay will not energize and the vehicle will not start because there will be no voltage supplied to the ignition system or fuel injectors. Also, sensor wiring is critical. This applies to all sensors in the fuel management system. Also, if the distributor has been replaced, it MUST be syncronized with the Crank position sensor. The pickup plate in the distributor is a Camshaft position sensor. You cannot adjust the timing by turning the distributor.