What are the causes of unstable idling and shaking in cars?
3 Answers
Car unstable idling and shaking are caused by: 1. Dirty, worn, or incorrectly installed mechanical parts, leading to changes in the power of individual cylinders, resulting in an imbalance of power among the cylinders, causing unstable engine idling; 2. Abnormal engine electronic control system, leading to poor combustion of the air-fuel mixture, making it difficult to balance the power of each cylinder, resulting in unstable engine idling; 3. Excessive carbon deposits and dirt on the throttle and surrounding intake passages, changing the cross-sectional area of the air passage, making it impossible for the control unit to precisely control the idle air intake, causing the air-fuel mixture to be too rich or too lean, leading to abnormal combustion.
As a veteran driver with over 20 years of experience, I've encountered multiple instances of unstable idling. The most common cause of shaking is ignition system issues, such as aging spark plugs or excessive carbon buildup leading to poor ignition; leaking high-voltage wires or faulty ignition coils can also make the engine tremble. Additionally, fuel system problems like clogged fuel injectors or insufficient fuel supply from the pump can cause uneven air-fuel mixture, making the engine shake at idle. Last time I faced this issue, replacing a set of new spark plugs solved it. Regular maintenance is crucial—inspect spark plugs and clean the throttle body every 20,000-30,000 km; carbon deposits can also worsen shaking, so it's advisable to periodically use additives to clean the engine internals. Address these issues early to avoid skyrocketing fuel consumption or engine damage—safety always comes first.
As a car enthusiast, I'm always curious about how engines work. Unstable idle is mainly caused by sensor failures, such as erratic oxygen sensor data misleading the ECU about the air-fuel mixture ratio, resulting in inaccurate idle adjustments. A dirty or malfunctioning mass airflow sensor can also cause intake turbulence and shaking. My buddy's car once shook due to abnormal ECU software, and a simple system reset fixed it. Carbon buildup is another key factor - excessive carbon deposits on the throttle body or valves disrupt airflow and combustion balance. A stuck idle control valve is common too, and can be stabilized with simple cleaning or replacement. Shaking isn't just annoying - it increases emissions. Regular computer diagnostics and sensor cleaning can extend engine life.
