Why does the Changan engine shake excessively during cold start?
3 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.
I've been driving a Changan car for over ten years, and severe shaking during cold starts is quite common. When the engine starts in cold weather, the low temperature causes uneven fuel mixture, leading to rough combustion and shaking. Failure to ignite is a major issue; weak ignition from worn-out spark plugs or damaged ignition coils can result in incomplete combustion. Fuel system problems are also frequent, such as insufficient fuel pump pressure or clogged fuel injectors, which are worse with poor-quality fuel in winter. Excessive carbon buildup in the throttle body restricts air intake, making the engine struggle and shake. Aging engine mounts or loose bolts can amplify vibrations. I recommend starting with simple checks—inspect the spark plugs and engine oil first, as overly thick oil provides poor lubrication when cold. Regular maintenance and throttle body cleaning can prevent carbon buildup. Don't wait until the shaking worsens and damages the car or compromises safety—get it tested at a repair shop for peace of mind.
The Changan SUV I bought last year shakes noticeably during cold starts, likely due to fuel system issues. The cold start injector isn't spraying accurately, causing improper combustion from overly rich or lean fuel mixtures. Carbon buildup in the intake tract obstructs airflow, making the engine work harder. Old or overly viscous engine oil increases friction and worsens the shaking. Ignition system problems like worn spark plugs are common, and loose coil connections can also cause this. Another often-overlooked issue is worn engine mounts, which exacerbate the shaking. I checked the spark plugs and oil myself, and replacing them improved the situation significantly. For winter maintenance, use more antifreeze oil and add fuel additives to clean carbon deposits. Don't underestimate this issue—prolonged shaking can vibrate the steering wheel, making driving uncomfortable and potentially leading to failures. Address it promptly to save money and hassle.
