Somehow flooded and wouldn’t start. Once got started I let the engine idle for 10 minutes and it did fibe but when put in reverse engine dies.
The problem might be with a dirty/defective Idle Air Control valve.
If this valve is plugged or fails to open when trying to start the engine, the engine will flood.
If this valve fails to go to the proper position when the transmission is shifted into gear, the engine will stall.
Tester
Another idea, less likely, leaky fuel injector. Fuel pressure hold test or fuel trim measurement might provide a clue. Diagnostic codes? Check engine light?