What Causes the Engine to Stall When Releasing the Throttle?

[McIris]

Releasing the throttle and causing the engine to stall is often due to fuel injector leakage or blockage, or throttle valve carbon buildup. The details are as follows: Fuel Injector Leakage or Blockage: If the fuel injector inside the engine leaks or becomes clogged, or if there is a circuit malfunction or insufficient fuel injection, it cannot spray fuel as instructed by the electronic control unit. This results in an overly lean or rich air-fuel mixture in the engine, causing poor combustion in certain cylinders and leading to engine stalling. Throttle Valve Carbon Buildup: The throttle valve controls the intake of air into the engine. After air enters, it mixes with gasoline to form a combustible mixture, providing power to the engine—acting like a valve regulating airflow. During engine operation, a portion of exhaust gases may enter the throttle valve. If not cleaned regularly, carbon deposits can accumulate on the throttle valve, increasing its resistance to opening and closing. This restricts normal airflow into the engine, leading to irregular engine operation and an increased likelihood of stalling.