What Causes Severe Idle Vibration?

[DiSimon]

Severe idle vibration can be attributed to the following main reasons: 1. Spark plug issues: If there is a malfunction in the car's ignition system spark plugs, it can lead to poor ignition system performance, inadequate spark plug firing, and other problems, resulting in unstable conditions such as vibration during idle. 2. Fuel quality problems: Poor fuel quality can damage engine performance, thus causing idle vibration issues. 3. Excessive engine carbon deposits: Too much carbon buildup inside the engine can cause the gasoline injected by the cold start injector to be largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture during cold starts and making it difficult to start.

[Juniper]

A few days ago, my car was shaking violently when stopping at a red light, with the entire seat vibrating, but it drove fine otherwise. After checking common causes, it's mostly due to old or dirty spark plugs not being replaced in time, which causes incomplete combustion and extra shaking. It could also be excessive carbon buildup clogging the fuel injectors, leading to poor fuel supply; or an air intake pipe leak, throwing off the air-fuel mixture ratio. I must remind everyone not to underestimate this issue—long-term shaking can easily damage the engine and waste fuel. I took apart the spark plugs myself and indeed found them blackened; replacing them fixed the problem. However, for those without experience, it's best to visit a professional repair shop for a thorough diagnosis—safety first.

[Sanders]

When encountering idle vibration, don't panic. As someone who often tinkers with cars, I'd try these self-check steps: Start the engine and listen for abnormal sounds; feel the engine cover to locate the vibration source; check the spark plugs and wire connections in the ignition system for looseness; inspect if the air filter is dirty; then verify if the fuel pump pressure is normal. Common causes include faulty ignition coils, vacuum tube leaks, or a stuck idle control valve. These minor issues accumulating can make the car shake, affecting driving comfort and increasing fuel consumption. Last time I discovered the problem, cleaning the throttle body and installing new spark plugs immediately alleviated it. DIY saved me a lot of money, and I highly recommend learning some basics under safe conditions.

[OIsaac]

Idle shaking is quite common, simply put, it's caused by engine instability. The reasons vary: old spark plugs causing poor ignition; clogged fuel injectors in the fuel system; air supply leaks or oxygen deficiency; excessive carbon buildup blocking the combustion chamber; or even broken engine mounts. This issue can severely degrade the driving experience, and long-term neglect may shorten the engine's lifespan. I must say, don't delay once you notice it, especially if the shaking worsens at high speeds, as it can pose hidden dangers. Prioritize checking the basic components—it's not expensive, and fixing them can restore smooth idle operation, making driving much more worry-free.

[DeOwen]

Why does the car shake severely at idle? Let me break it down: Incomplete combustion at low engine speeds may be caused by aging ignition components like spark plugs failing to provide a stable spark; or fuel supply issues such as a clogged fuel filter restricting flow; carbon deposits accumulating near the valves reducing efficiency; and damaged engine mounts unable to absorb vibrations. These common flaws can intensify the shaking, which I notice becomes more obvious when the AC is on. Understanding these details helps avoid pitfalls—I recommend regular replacement of small parts for maintenance to prevent sudden breakdowns.