Why Does the Car Shake Severely During Cold Start?

[LaIsabel]

Here are the reasons for severe shaking during cold start: 1. Insufficient engine temperature: When starting a cold car, the engine temperature is similar to the surrounding environment, which is not suitable for engine operation. In low temperatures, fuel atomization is poor, leading to reduced ignition energy and affecting power performance, causing the car to shake. This phenomenon occurs more frequently in winter, so parking the car in a garage can alleviate engine shaking. 2. Inaccurate air-fuel mixture ratio: During cold starts, the engine oil viscosity is high, and components are not fully lubricated, easily leading to an inaccurate air-fuel mixture ratio. The car's computer may misjudge, reducing power output and causing shaking. 3. Carbon deposits in the car: Carbon buildup is one of the significant reasons for shaking during cold starts. Daily driving conditions and habits can lead to varying degrees of carbon deposits. Excessive carbon deposits on valves and intake pipes can make cold starts difficult and cause insufficient power or even stalling while driving. If carbon deposits are severe, prompt cleaning is necessary. If unable to resolve it yourself, seek professional help at a 4S shop.

[OVera]

I've found that severe shaking during cold starts is mostly caused by unstable engine operation at low temperatures, especially when spark plugs are aged or there's severe carbon buildup. Worn spark plugs lead to poor ignition, resulting in incomplete combustion that makes the car shudder; carbon deposits accumulating in the throttle body or fuel injectors can block fuel passages, causing uneven fuel delivery. Additionally, engine oil with too low viscosity may provide insufficient lubrication in cold weather, exacerbating the shaking. For prevention, I prefer using high-quality gasoline to reduce carbon deposits, cleaning throttle body carbon buildup every 30,000 kilometers, selecting engine oil suitable for local climate conditions, and avoiding frequent short-distance driving. If shaking occurs, don't drive off immediately - try idling for a few minutes first. If the shaking persists, check if spark plugs need replacement, or have a professional technician diagnose potential ignition system or fuel delivery issues.