What Causes Intermittent Shaking When the Car is in Neutral?
2 Answers
Intermittent shaking when the car is in neutral is caused by issues such as leaks in the intake manifold or various valves, or excessive carbon buildup in the throttle body or intake passages. Below are some related explanations for car shaking: 1. Dirty throttle body or excessive carbon buildup in fuel injectors: After driving for a certain distance, a dirty throttle body can cause it not to close properly or the idle stepper motor to get stuck, both of which can lead to excessively high engine idle speed. Carbon buildup generated during engine operation can also cause vehicle shaking, especially when starting the car. The engine may shake more violently than usual, and sometimes it may even fail to start on the first try. 2. Worn engine mounts: Car shaking can sometimes be related to aging engine mounts. Engine mounts are essentially the shock absorption system for the engine, responsible for absorbing minor vibrations during engine operation. If the engine mounts are faulty, these vibrations can be transmitted to the steering wheel and the cabin, causing shaking during idle.
I'm all too familiar with the issue of car shaking in neutral after driving for twenty years. It's mostly caused by unstable engine operation, and the most common culprit is worn-out spark plugs. Last time my old buddy was shaking like a sieve, I took it apart and found two out of four spark plugs severely eroded. Carbon buildup in the throttle body is another troublemaker, especially for those frequently stuck in traffic or driving at low speeds. Too much carbon reduces air intake, making the engine 'gasp for breath' and shake. Engine mounts aging is also a factor—rubber parts harden and crack over time, reducing their damping effect, and you can even feel the vibration in the steering wheel. Additionally, clogged fuel injectors or poor fuel supply can cause intermittent shaking. If these issues aren't addressed promptly, beware of cold-start difficulties or a sudden spike in fuel consumption.
