Why does the Changan engine shake excessively during cold start?
1 Answers
The excessive shaking of a Changan engine during cold start is mainly caused by the following reasons: 1. Improper air-fuel mixture ratio. The air-fuel mixture ratio is inaccurately adjusted, occurring in both open-loop and closed-loop control systems. In vehicles with closed-loop control, the oxygen sensor's minimum operating temperature is 37°C. If the vehicle has just been started, the exhaust pipe temperature may not reach 37°C, preventing the oxygen sensor from functioning. As a result, the ECU makes incorrect judgments, leading to errors in controlling the air-fuel mixture and ignition timing through the actuators, thereby reducing the engine's power output and causing shaking. 2. Carbon deposits on valves and intake ports. If carbon deposits accumulate on the engine's valves and intake ports, they can absorb a certain amount of fuel, causing the ECU to make incorrect judgments. 3. Uneven cylinder conditions. In multi-cylinder engines, spark plugs may also exhibit the aforementioned issues. After prolonged use, the ignition gap and timing control of spark plugs may vary, but the ECU cannot detect this deviation and continues to treat them equally, resulting in discrepancies between actual and theoretical performance. This leads to some cylinders producing less power, causing shaking. 4. Faulty coolant temperature sensor. The coolant temperature sensor is one of the key inputs for the ECU to determine the engine's operating condition. If the engine is cold-started at -10°C, but the sensor reports a temperature of 20°C to the ECU, the ECU will inject fuel based on the 20°C condition, resulting in insufficient fuel supply and causing shaking.
