Why does vehicle start up and then shut off? on 1997 Honda Accord

Vehicle sat up for 1.5 yrs. Have flushed complete fuel system. Installed new fuel pump, filter, regulator. Cleaned fuel injectors. Fuel delivery working properly as is ECM fuel control. No DTC's. Good Spark and timing belt good.

2 answers
Clean your egr valve could be dirty or the valve stuck or corroded
It's located on on top the intake manifold closed to your vtech solenoid
IF when cranking to start it , you dont let the key back to the 'run' position as quickly ,will it continue running a little longer? ......Might be a faulty electrical portion of the ignition switch.Can be tested if your equipped.