What Causes Engine Shaking During Cold Starts?

[DeLaura]

Engine shaking during cold starts can be attributed to the following reasons: 1. Incorrect air-fuel mixture ratio, where the fuel-air mixture is improperly calibrated, occurring in both open-loop and closed-loop control systems. In vehicles with closed-loop control, the oxygen sensor operates at 370 degrees Celsius; 2. Carbon buildup on valves and intake ports. If carbon deposits form on the engine's valves and intake ports, they can absorb a certain amount of fuel, leading to incorrect ECU judgments; 3. Uneven cylinder conditions. After prolonged engine use, the clearance between each cylinder liner and piston may vary, with larger clearances allowing some high-temperature gases to leak, reducing power output; 4. Faulty coolant temperature sensor. If the engine starts at -10 degrees Celsius but the sensor reports 20 degrees Celsius to the ECU, the ECU will inject fuel based on 20-degree conditions, resulting in insufficient fuel and causing shaking.