What causes unstable idling, shaking, and frequent stalling when the engine is warm?
2 Answers
The reasons for unstable idling, shaking, and stalling are as follows: 1. Severe engine carbon deposits. The most common cause of car shaking is a dirty throttle body or excessive carbon buildup in the fuel injectors. 2. Ignition system issues. Check the condition of the spark plugs, high-voltage wires, and ignition coils. Poor performance of the ignition system or faulty spark plug firing can also lead to such symptoms. 3. Unstable fuel pressure. If you have already cleaned the engine carbon deposits, cleaned the throttle body, replaced the gaskets and spark plugs, but still notice shaking during idling, it is recommended to visit a 4S shop to check the fuel supply pressure and the intake pressure sensor. Abnormal fuel pump pressure or incorrect readings and poor performance of the intake pressure sensor can cause the car to shake. 4. Aging engine components. Car shaking can also be related to the aging of engine mounts (also known as engine mounts). Engine mounts are essentially the shock absorption system of the engine, responsible for absorbing minor vibrations during operation. If the engine mounts are faulty, these vibrations can be transmitted to the steering wheel and the interior of the car, causing shaking during idling.
Last month, I also encountered the issue of unstable idle speed, shaking, and stalling when the engine was warm. While driving home, the engine seemed to be dancing and suddenly stalled several times. It was most likely due to severe carbon buildup in the throttle body, where dirt blocked the intake, causing insufficient airflow, and the spark plugs were too old to ignite properly. If the idle control valve is stuck or broken, idle speed regulation goes out of control. Problems in the fuel system, such as clogged fuel injectors or insufficient fuel pump pressure, can also cause unstable idling due to poor fuel delivery. Faulty sensors like the mass airflow sensor can send incorrect data, leading to improper adjustments by the engine control unit. Prolonging this issue is bad for the engine, increasing wear and wasting fuel. Cleaning the throttle body yourself might help temporarily, but for safety, I quickly went to a repair shop for a full inspection of the electrical and exhaust systems. After the repairs, the idle became much more stable—safety first, don’t delay.
