What Causes the Vibration Felt When Idling in the Car?

[DavidRose]

The reasons for feeling vibration when idling in the car are: 1. Malfunction in the vehicle's ignition system; 2. Loose components in the ignition system; 3. Severe carbon buildup in the engine; 4. Aging engine components; 5. Excessive carbon deposits in the throttle body; 6. Untimely replacement of the air filter; 7. Excessive carbon buildup in the fuel injectors; 8. Problems with the ignition system; 9. Unstable oil pressure. Idling in a car does not refer to a speed but rather to an operating condition. When the engine runs without load, it is called idling. When the engine is running and the accelerator pedal is fully released, the engine is in an idle state. The engine speed during idling is called the idle speed, which can be adjusted by modifying the throttle opening size.

[MaximusFitz]

My previous car used to shake a lot when idling at red lights, which was really uncomfortable. The main reason was issues with the ignition system, such as worn-out spark plugs or faulty ignition coils, causing unstable ignition and making the engine vibrate erratically. If the rubber mounts of the engine supports were worn, the vibrations would directly transmit to the cabin. Another issue was excessive carbon buildup in the fuel system, leading to uneven fuel injection and causing shaking. Temperature also played a role, especially during cold starts. It's recommended to regularly inspect these components, replace spark plugs, and clean the throttle body, which can significantly improve the situation. With an older car, you need to be proactive—don't wait until the shaking gets severe to fix it, as it affects both safety and fuel efficiency.

[DiRiver]

As a driver who frequently takes long-distance trips, the idle vibration in the car can be quite annoying, especially when the air conditioning is on during summer. The common causes include loose engine mounts or clogged fuel filters, which lead to uneven fuel supply and vibrations. Another possible reason is poor tire balance, which amplifies the vibrations. Regular maintenance is essential—for example, replacing the air filter can reduce carbon buildup, and checking the ignition system, including coils and spark plugs, can extend the engine's lifespan. If the vibration becomes severe, it's important to pull over and check for unusual noises. Ignoring it could damage more components. For family trips, extra caution is needed—comfort and safety should always come first.

[SanMax]

Idle shaking may be caused by carbon buildup on the spark plugs or a faulty ignition coil, as poor ignition leads to unstable engine operation and vibration. Worn engine mount bushings also transmit vibrations, making them more noticeable inside the car. Dirty fuel injectors causing uneven fuel supply can also be a culprit. Regular maintenance is key—inspect the ignition system every six months, replace spark plugs, and clean fuel injectors to reduce vibrations. Avoid low-quality fuel to prevent carbon buildup and maintain engine health.