What Causes Engine Shaking During Cold Start?

[ZaneLynn]

Reasons for engine shaking during cold start are as follows: 1. Incorrect Air-Fuel Ratio: Improper air-fuel mixture occurs when the fuel-air mixture is inaccurately proportioned, existing in both open-loop and closed-loop control systems. In vehicles with closed-loop control, the oxygen sensor's operating temperature is 370°C. 2. Carbon Deposits: Carbon buildup on valves and intake passages. If carbon deposits form on engine valves and intake passages, they can absorb a certain amount of fuel, causing the ECU to make incorrect judgments. 3. Cylinder Conditions: Uneven cylinder performance. After prolonged engine use, the clearance between each cylinder liner and piston will vary. Larger clearances in certain cylinders allow high-temperature gases to leak, reducing power output. 4. Faulty Coolant Temperature Sensor: If the coolant temperature sensor malfunctions - for example, when the actual engine temperature is -10°C during cold start but the sensor reports 20°C to the ECU - the computer will inject fuel based on 20°C conditions, resulting in insufficient fuel supply and causing shaking.