Why does the car vibrate at idle speed?
2 Answers
Car idle vibration is caused by engine carbon deposits, aging or carbon buildup in spark plugs, dirty engine throttle, poor fuel flow, or ignition system failure. More detailed information is as follows: 1. Engine carbon deposits: Engine carbon deposits result from various reasons, but most are due to poor driving habits of the owner. Components such as ignition coils, spark plugs, and high-voltage wires have their service life. Once problems arise, they can lead to poor ignition system performance, resulting in idle vibration. 2. Spark plug carbon deposits: Among these, spark plug carbon deposits are particularly severe. This requires the owner to check if there is carbon buildup in the spark plugs. If there is excessive carbon buildup, replace them regularly. Ignition system failures should be addressed promptly, as severe cases can cause the engine to fail to start or even suddenly stall during driving, leading to unnecessary trouble.
I remember one time my car started shaking while waiting at a red light, and I could feel the entire steering wheel trembling. This situation is generally caused by unstable engine operation at idle speed, most commonly due to aging rubber engine mounts. These mounts are responsible for cushioning vibrations and can harden or crack over time. Faulty spark plugs are another common cause—if ignition timing is off, the cylinders won't work evenly, leading to shaking. When I last took my car to the repair shop, the mechanic also mentioned that carbon buildup affecting the intake tract or a dirty throttle body can cause unstable idling. My advice is not to delay—first check and replace the mounts or spark plugs, as the cost isn't too high. If the shaking worsens and is accompanied by a humming noise, it might indicate internal engine issues. It's best to get a comprehensive diagnosis as soon as possible to avoid minor problems turning into major repairs.
