What Causes Unstable Idle and Car Shaking?
2 Answers
Unstable idle and car shaking can be caused by issues with spark plugs or high-voltage coils, severe engine carbon buildup, or unstable oil pressure. Here are some extended details: Checking spark plugs: The likelihood of high-voltage coil damage is actually quite low. Simple cleaning can be done. If the idle shaking persists after replacing the spark plugs, then consider checking the condition of the high-voltage wires and ignition coils. Poor performance of the ignition system or bad spark plug firing can also lead to such fault symptoms. Severe engine carbon buildup: The most common cause of car shaking is a dirty throttle body or excessive carbon buildup in the fuel injectors. When there is too much carbon buildup inside the engine, the gasoline sprayed by the cold-start injector can be largely absorbed by the carbon deposits, resulting in an overly lean mixture during cold starts and making it difficult to start. Unstable oil pressure: If you have already cleaned the engine carbon buildup, cleaned the throttle body, replaced the oil gasket and spark plugs, and still notice car shaking during idle, it is recommended to visit a 4S shop to check the fuel supply pressure and the intake pressure sensor. Abnormal fuel pump supply pressure or incorrect readings and poor performance of the intake pressure sensor can all cause car shaking.
I think the car's unstable idling and shaking are mainly related to ignition system failures, such as aging spark plugs or faulty ignition coils, which cause irregular ignition and uneven combustion. Once, my car shook violently at a red light, and after inspection, it was found that the spark plug gap was too large. After replacing them with new ones, it ran smoothly again. Sensors are also crucial; a dirty mass airflow sensor or a failed oxygen sensor can cause the ECU to miscalculate the fuel injection amount, leading to fluctuating idle speeds. Excessive carbon buildup in the engine, especially carbon deposits on the throttle body and intake manifold, affects airflow and results in sluggish throttle response. On the fuel side, clogged fuel injectors or insufficient fuel pump pressure can cause uneven fuel delivery, leading to shaking. Additionally, vacuum leaks or cracked hoses can cause abnormal air intake, resulting in fluctuating engine speeds. In short, if these issues aren't fixed promptly, they can accelerate wear and increase fuel consumption. It's best to get a comprehensive inspection to prevent potential hazards.
