What Causes Car Engine Shaking During Ignition?

[DelDaisy]

Reasons for car engine shaking during ignition: 1. Poor fuel quality: In winter when temperatures are low, during cold starts the engine block temperature is too low for proper fuel atomization, causing insufficient mixing of fuel and air in the combustion chamber, leading to difficult starts and severe body shaking; 2. Spark plugs: The gap between spark plug electrodes gradually widens, reducing ignition energy and causing poor fuel atomization; 3. Ignition coils: Aging ignition coils, or aging/sparking high-voltage wires from spark plugs, result in decreased ignition energy; 4. Carbon buildup on engine valves and intake manifold: Since carbon deposits can absorb some fuel, the ECU makes incorrect judgments - while it controls injection of 100 units of fuel-air mixture, only 90 units actually enter the cylinder. Even if these 90 units burn completely, they still can't provide sufficient power, making shaking inevitable.