Throttle body: The throttle body controls the amount of air and fuel that enters the engine. When the throttle body is dirty or damaged, it can cause the engine to stall when the car is stopped or put into gear.
Fuel injector: The fuel injectors are responsible for spraying fuel into the engine's cylinders. When a fuel injector is dirty or clogged, it can cause the engine to misfire and stall when the car is stopped or put into gear.
Spark plugs: The spark plugs are responsible for igniting the fuel in the engine's cylinders. When the spark plugs are worn or damaged, it can cause the engine to misfire and stall when the car is stopped or put into gear.
Oxygen sensor: The oxygen sensor is responsible for monitoring the amount of oxygen in the engine's exhaust. When the oxygen sensor is not working properly, it can cause the engine to run rich or lean, which can lead to stalling when the car is stopped or put into gear.
Vacuum hose leaks: Vacuum hose leaks can cause the engine to idle rough and stall when the car is stopped or put into gear.
Faulty transmission or clutch: In vehicles with automatic transmissions, a faulty transmission or clutch can cause the engine to stall when the car is stopped or put into gear.
