What Causes Car Shaking During Ignition?

[GideonMarie]

Car shaking during ignition is mainly caused by the following reasons: 1. Poor fuel quality. Low-quality fuel has poor volatility, especially in winter when temperatures are low. During a cold start, the engine block temperature is low, making it difficult for the fuel to atomize. This results in insufficient mixing of fuel and air in the combustion chamber, leading to difficulty starting and severe body shaking. 2. Carbon buildup in the engine valves and intake manifold. Since carbon deposits can absorb a certain amount of fuel, the electronic control unit (ECU) makes incorrect judgments. For example, if the ECU assumes it is injecting 100 units of fuel-air mixture, but only 90 units actually enter the cylinder, even if the remaining 90 units burn completely, the required power output will not be achieved. 3. Spark plug issues. During a car start, especially when fuel and lubricant temperatures are low, more fuel is needed to meet power demands. Over time, the electrode gap in the spark plug gradually widens, reducing ignition energy and impairing fuel atomization, which causes the car body to shake.