If your vehicle is showing engine stalls immediately after starting, here are the most likely causes and the parts you'll need to fix each one.
If the vehicle's security system does not recognize the transponder chip in the key, it will allow the engine to start briefly before intentionally cutting off the fuel injectors or ignition.
The engine needs extra bypass air to maintain an idle immediately after starting. If the idle air control valve or throttle body is clogged with carbon buildup, the engine will choke and stall unless you press the gas pedal.
The engine computer relies on this sensor to measure incoming air. If it is unplugged (often forgotten after checking the air filter) or heavily contaminated, the engine starts on a default fuel map but stalls the moment it tries to read the sensor.
A large unmetered air leak leans out the air-fuel mixture so severely that the engine cannot sustain combustion. This frequently happens if a large hose, like the PCV or brake booster line, is left disconnected after recent engine work.
The fuel pump may prime the system just enough to start the engine, but fail to maintain pressure once running. A faulty relay can also cut power to the pump immediately after the key drops from the 'Start' to the 'Run' position.
The Exhaust Gas Recirculation (EGR) valve should be completely closed at idle. If it gets stuck open due to carbon chunks, exhaust gases will flood the intake manifold and suffocate the engine immediately upon startup.