If your vehicle is showing engine stalls while idling or stopped at a light, here are the most likely causes and the parts you'll need to fix each one.
Carbon buildup in the throttle body or a failing IAC valve restricts the small amount of air needed to keep the engine running at idle. This is a very frequent maintenance issue that starves the engine of air when your foot is off the gas.
A cracked vacuum hose, failing PCV valve, or leaking intake gasket lets unmetered air into the engine, leaning out the air/fuel mixture and causing a stall. This often happens if a hose is accidentally left disconnected after recent engine work or an oil change.
The MAF sensor measures air entering the engine so the computer can inject the right amount of fuel. If it gets dirty (often from a neglected air filter), it miscalculates the air at low RPMs, causing the engine to stall.
Old spark plugs or weak ignition coils can struggle to ignite the fuel mixture efficiently at low engine speeds. This leads to a rough, stumbling idle and an eventual stall when stopped.
The Exhaust Gas Recirculation (EGR) valve is supposed to close at idle. If carbon buildup causes it to stick open, it floods the engine with exhaust gases, choking it out when you come to a stop.
In automatic transmissions, if the torque converter clutch fails to disengage when coming to a stop, it acts exactly like forgetting to press the clutch pedal in a manual car, violently stalling the engine.