What Causes the Engine to Stall When Releasing the Throttle?
3 Answers
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.
As an ordinary car owner, I've experienced situations where the car stalls when releasing the accelerator pedal, which can be quite troublesome. This might be caused by issues with the idle speed control system, such as a stuck idle control valve or excessive carbon buildup obstructing airflow. Alternatively, it could be a faulty throttle position sensor providing inaccurate readings. Other potential causes include fuel system problems like clogged fuel injectors leading to insufficient fuel supply at idle, a dirty air filter disrupting air intake balance, or minor vacuum leaks disturbing the air-fuel mixture ratio. After cleaning the throttle body myself, the situation improved. However, if the problem recurs, it's essential to visit a professional workshop for diagnostic trouble code scanning, as sudden stalling in urban traffic can be dangerous and may cause accidents. For regular maintenance: clean relevant components every 10,000 kilometers and use fuel additives to reduce carbon deposits. Remember not to neglect minor issues - safe driving should always be the top priority.
From a repair experience perspective, I've observed that stalling upon throttle release often stems from issues like a faulty or carbon-jammed idle air control valve (regulates low-speed airflow), a dirty throttle body restricting opening, or sensors such as the MAP providing erroneous data. Unstable fuel pressure or clogged filters can also trigger it, as insufficient fuel injection at idle leads to stalling. An EGR valve stuck open causes excessive exhaust gas recirculation. Vacuum leaks commonly occur at intake manifold cracks. In cases I've handled, cleaning the IAC valve and throttle body restored normal operation. Improper ECU settings may require resetting. For diagnosis, using an OBD scanner to check codes and inspect component connections is advised. Never overlook risks like highway stalling posing rear-end collision threats—prompt repairs prevent greater losses. Regular 20,000-km maintenance effectively prevents such issues.
