Why does the vehicle shake severely during cold start?
2 Answers
The main reasons for severe shaking during cold start of a vehicle are: 1. In low-temperature environments, the engine's internal temperature is insufficient. Therefore, more fuel injection is required during cold start to meet power demands. However, larger spark plug gaps result in smaller ignition energy. Poor fuel atomization at low temperatures requires higher ignition energy. Prolonged vehicle use can cause the spark plug gap to widen, leading to decreased ignition energy, which affects power performance and causes the vehicle to shake. 2. Ignition coil failure. The ignition coil is a transformer responsible for converting the vehicle's low-voltage current into high-voltage electricity, providing sufficient voltage for the spark plug to generate sparks. If the ignition coil fails, such as cracking or leaking electricity, it will result in insufficient or lack of spark plug ignition capability. Consequently, the air-fuel mixture in this cylinder will not combust properly, leading to engine misfire, difficult starting, and acceleration shaking.
Severe shaking during cold vehicle start-up is usually caused by unstable engine operation before it fully warms up. Carbon deposits accumulated in the fuel injectors or valves are the main culprits, disrupting fuel mixture flow and causing uneven ignition; old spark plugs with poor ignition performance may also trigger shaking; aging and loose rubber engine mounts failing to absorb vibrations; or high viscosity of engine oil in low temperatures leading to poor lubrication exacerbating the issue. These are more common in high-mileage vehicles or those frequently used for short trips. Regular checks for carbon deposits in fuel injectors, cleaning, and spark plug replacement are recommended. If shaking is noticeable along with starting difficulties, it might indicate a fuel pump or sensor malfunction. For safety, don't ignore it—I advise seeking professional diagnosis early to prevent increased fuel consumption or worse mechanical failures.
