If your vehicle is showing engine stalls when coming to a stop or while idling, 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 prevents the engine from getting enough bypass air to maintain a steady idle when your foot is off the gas pedal.
Unmetered air entering the engine leans out the air/fuel mixture, causing a rough idle and stalling. If it stalls specifically when pressing the brake pedal, a leaking brake booster or its vacuum hose is highly suspect.
The MAF sensor measures air entering the engine. If it is dirty (often from over-oiled aftermarket air filters) or failing, it sends incorrect data to the computer, leading to improper fueling and stalling at low RPMs.
The Exhaust Gas Recirculation (EGR) valve should be closed at idle. If carbon buildup causes it to stick open, exhaust gases flood the intake manifold and choke the engine out when coming to a stop.
In automatic transmissions, if the torque converter clutch stays locked when coming to a stop, it acts exactly like a driver forgetting to press the clutch pedal in a manual car, violently stalling the engine.
A failing fuel pump or heavily clogged fuel filter may struggle to maintain adequate fuel pressure at low engine speeds, causing the engine to starve and stall when dropping to idle.