1988 chevy 3500 truck 454 engine stalled while running 50mph then backfired when restarted but then continued to run properly. was able to drive 3 miles no problem, shut engine down waited a couple of hours then started engine ran fine about 5 miles engine stalled cut off, placed gear in neutral and restarted, engine backfired very loud shuttered and cut off. pulled over started engine it would idle, put timing light on and timing was correct, but still backfired after starting down road cut off and would not restart, have recently replaced plugs, plug wires, distributor cap,rotor button, coil, throttle position sensor, and fuel filter. engine seems to not be getting any fire when turning over