Why does the car shake when idling?
2 Answers
The reasons for car shaking during idling are: When the engine is running, the engine oil does not follow up in time, causing the engine to lack good mechanical operating conditions or poor fuel injector atomization, and improper idle adjustment leads to engine shaking. Car idling shaking is a common phenomenon, and slight idling shaking is normal. If you notice obvious body shaking when starting the vehicle or when the vehicle is parked with the engine still running, it is usually due to severe engine carbon deposits or a dirty throttle. When there is excessive carbon buildup inside the engine, the gasoline sprayed by the cold start injector will be largely absorbed by the carbon deposits, resulting in an overly lean mixture during cold starts and making it difficult to start. In this situation, the car will only start easily once the carbon deposits have absorbed enough gasoline to reach saturation. After starting, the gasoline adsorbed on the carbon deposits will be sucked into the cylinder by the engine's vacuum suction force and burned, making the mixture too rich. The combustible mixture in the engine alternates between being too lean and too rich, causing idle shaking after a cold start.
Last time my friend's Lavida was shaking like a massage chair, and it turned out to be worn engine mounts. The rubber parts hardened and cracked after long-term use, reducing their damping effect. Another common reason is worn spark plugs. When the electrodes are eroded, the ignition becomes poor, and if a cylinder isn't working properly, the engine shakes like it's limping. A dirty air filter can also cause shaking due to restricted airflow—just like someone trying to run with their mouth covered. The most troublesome issue is a dirty throttle body, which controls the air intake. Too much carbon buildup affects its opening and closing accuracy, causing unstable idle speed. My advice is to start by checking the cheaper components first—don't let the repair shop trick you into cleaning the fuel system right away.
