What Causes Cold Start Shaking?
2 Answers
Causes of car cold start shaking mainly include: 1. Improper air-fuel mixture. 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 370 degrees Celsius. 2. Carbon deposits on valves and intake ports. If carbon deposits form on the valves and intake ports inside the engine, they can absorb a certain amount of fuel, causing the ECU to make incorrect judgments. 3. Uneven cylinder conditions. After prolonged use of the engine, the gap between each cylinder liner and piston can vary in size—some gaps are larger, while others are smaller. During a cold start, without proper oil lubrication, larger gaps in the cylinders can allow leakage of high-temperature gases, reducing power output. 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-starting at -10 degrees Celsius, but the sensor "tells the ECU the temperature is 20 degrees Celsius," the ECU will inject fuel based on a 20-degree condition. Naturally, the fuel amount will be insufficient, leading to shaking.
There are quite a few reasons for cold start shaking. I've been driving this car for several years and have encountered this situation a few times. The most common cause is aging or damaged spark plugs, leading to incomplete ignition, which is especially noticeable when the engine is cold. Carbon buildup in the fuel injectors is also a problem, causing uneven fuel distribution in the cylinders due to poor atomization. If the ignition coil is faulty, unstable power supply can also cause shaking. Additionally, engine oil being too thick at low temperatures can lead to insufficient lubrication, causing poor piston movement. I once fixed it myself by simply cleaning the throttle body and replacing the spark plugs, and it was restored. However, it's recommended to address the issue promptly; otherwise, prolonged neglect can lead to increased wear and higher repair costs. Paying attention to these components during regular maintenance can help prevent such issues.
