Why does the engine occasionally shake when waiting at a red light?

[VonClara]

The main reason for the occasional engine shaking when waiting at a red light is: This is a resonance phenomenon caused by the engine, frame, steel plates, and tires. The solution is mainly to adjust the engine speed slightly higher or lower. This occurs due to natural wear or deformation of bearings and ball joints. Many minor deformations are completely imperceptible to the naked eye, but as the vehicle speed increases and centrifugal force grows, the oscillation effect caused by bearing deformation becomes more pronounced; hence, the faster the speed, the greater the shaking. Here is some additional information: Functions and types: An engine is a machine capable of converting other forms of energy into mechanical energy, including internal combustion engines, external combustion engines, jet engines, electric motors, etc. For example, internal combustion engines typically convert chemical energy into mechanical energy. Introduction and history: The term engine can refer to both the power generation device and the entire machine including the power unit. The engine was first invented in the UK, so the concept of an engine also originates from English, with its original meaning referring to "a mechanical device that generates power."

[StKarter]

After repairing cars for so many years, I often see this situation. The engine occasionally shakes when waiting at a red light, mainly caused by unstable idling. Common reasons include aging spark plugs leading to low ignition efficiency, or carbon deposits clogging the fuel injectors affecting uniform fuel injection. Dirty throttle valves are also a significant factor—driving frequently in congested areas causes severe carbon buildup, and when parked, reduced air flow makes the engine prone to shaking. If the engine mounts are worn, they can amplify minor vibrations into large shakes. This isn't a major issue, but it should be addressed promptly: first try using some fuel system cleaner, and regularly replace spark plugs and air filters. If the shaking becomes frequent or severe, it could indicate faulty ignition wires or coils—it's best to have a professional shop check it to avoid higher repair costs later.

[DeSophie]

My car sometimes shakes a few times when stopped at a red light. After checking, I found it's quite common. Possible reasons include poor fuel quality or insufficient fuel supply, where unstable fuel pump pressure makes the engine gasp; or the AC being on, consuming more power and increasing system load, which worsens the vibration. Engine mount gaps can also amplify the shaking. Try driving gently, using high-quality gasoline, and adding fuel additives to clean the internals. Turn off non-essential electronics when parked to see if it improves. It's not an emergency issue, but regular maintenance like changing the oil filter can prevent it. You can pay attention to: whether there are any unusual noises when listening, and if the engine starts smoothly. Small issues left unfixed may lead to increased fuel consumption.

[SanAdriana]

Having driven for ten years, I've seen plenty of engine shaking at red lights. It's usually an idle speed issue: carbon buildup in the throttle body restricts air intake, and worn spark plugs cause uneven ignition. Cracked engine mounts are also common. The solution is simple: clean the throttle body every 20,000 kilometers and replace spark plugs every 50,000 kilometers. Avoid prolonged low-speed driving in traffic to reduce carbon buildup. Minor shaking doesn't affect daily use, but aging can reduce power and fuel efficiency. Better driving habits, like less sudden braking and hard acceleration, can extend engine life.