Car won't start anymore, had idling problems

I have a 1982 Datsun 280zx that has developed some problems. It's an L28ET. It started having issues with idling, it will die if you don't press the gas and brake pedal. But it wouldn't restart. It has brand new alternator, starter, fuel pump, fuel filter, spark plugs, thermostat, rebuilt radiator, belts, and some hoses. Replaces all exhaust system as well as fuel lines. The check engine light also came on before. Any ideas what could be the problem? Would be greatly appreciated. Thanks.