What causes severe shaking when the car is cold but normal when warm?

[PaisleeRose]

Severe shaking when the car is cold but normal when warm could be due to inaccurate air-fuel mixture ratio, which may occur in both open-loop and closed-loop control systems. If the car's computer makes an incorrect judgment, it may cause errors in controlling the air-fuel mixture and ignition timing through the actuators, thereby reducing the vehicle's power output and resulting in shaking. Another possible reason is low temperature. When the engine temperature is insufficient, more fuel should be injected during cold starts to meet power requirements. The larger the spark plug gap, the smaller the ignition energy. During low temperatures, fuel atomization is poor, requiring higher ignition energy. Over time, the ignition gap of spark plugs tends to increase, leading to reduced ignition energy, which affects power performance and causes shaking. Additionally, aging ignition coils, high-voltage wires of spark plugs, or leakage can also result in decreased ignition energy.

[OJesse]

My old car sometimes shakes violently when starting in the morning, with the whole body trembling, but it becomes completely normal after driving about one kilometer. This issue is commonly caused by excessive carbon buildup or aging spark plugs, where fuel particles are harder to ignite when the engine is cold, leading to uneven combustion and shaking. I once tried cleaning the carbon deposits myself, and it worked quite well. Another possibility is high oil viscosity, which causes insufficient lubrication when the engine is cold, increasing friction. Or it could be a sensor malfunction, such as an inaccurate oxygen sensor leading to irregular fuel supply. If not addressed promptly, it may consume more fuel or even damage the engine. I recommend checking the carbon buildup and ignition system as soon as possible to avoid bigger problems. Regularly changing the air filter and engine oil can help prevent this issue—safety first.

[JoelAnn]

Having driven for ten years, I've encountered this situation: the engine shivers like it's trembling when starting cold, but once warmed up, it's as if nothing's wrong. At first, I was startled, thinking it was a serious fault, but later the mechanic told me it was mainly due to bad spark plugs or clogged fuel injectors. When the engine is cold, the low temperature slows fuel evaporation, causing rough ignition and shaking; once warmed up, the system adapts and runs smoothly. Additionally, aging engine mounts can make the body shake more noticeably. I remember my car wasn't repaired in time, and later the fuel consumption increased significantly. Now, I regularly maintain the spark plugs to ensure smooth starts. Don't take it lightly—get it checked at a professional shop early to avoid the hassle of breaking down midway.

[VonJourney]

This phenomenon is quite common, primarily due to mechanical differences caused by temperature variations. When the engine is cold, its low temperature makes it difficult for carbon deposits or aging ignition components like spark plugs to ignite the air-fuel mixture properly, resulting in unstable combustion and shaking. Once the engine warms up and components expand to their proper positions, it runs smoothly. Another possible cause could be poor oil circulation leading to abnormal friction, or a clogged air filter restricting airflow. Long-term neglect may result in engine knocking or additional wear. It's advisable to inspect those components. I often help friends with their cars, and usually, cleaning carbon deposits or replacing spark plugs solves the issue. Just avoid using low-quality fuel.