Why does a car engine shake when cold?
2 Answers
There are mainly 3 reasons why a car engine shakes when cold: 1. Excessive carbon deposits in the engine can cause shaking during cold starts: When a certain amount of carbon deposits accumulate in the engine, they absorb some of the fuel-air mixture, leading to incomplete combustion. This results in insufficient power output and causes the vehicle to shake during driving. 2. Engine misfire can cause this issue: It might be due to one cylinder not working or multiple cylinders not functioning. In this case, the engine will experience noticeable vibration, leading to shaking of the vehicle. 3. The oxygen sensor not reaching operating temperature: The minimum working temperature of an oxygen sensor is 370 degrees Celsius. During cold starts, the oxygen sensor cannot function properly, causing certain judgment errors when transmitting data to the ECU. This leads to deviations in fuel-air mixture control and ignition timing, inevitably reducing the engine's power output and causing some shaking phenomenon.
Last time my car shook when starting cold, even the steering wheel moved, which was scary. Thinking carefully, there are several common reasons: First, the spark plugs are old or the gap is incorrect, causing inaccurate ignition timing, especially in winter when the temperature is low, leading to incomplete fuel combustion and more shaking. Second, too much carbon buildup in the throttle body blocks the air intake, making the engine struggle to breathe, resulting in insufficient oxygen when the car is cold. Third, the fuel injectors are clogged or dirty, causing uneven fuel injection and unstable combustion. Fourth, faulty sensors like the coolant temperature sensor mislead the ECU into incorrectly adjusting the air-fuel ratio. Fifth, the engine oil is too thick, providing insufficient lubrication, and flows slowly in cold weather. It's recommended to warm up the car for 2-3 minutes after each cold start and drive gently to allow proper warm-up. Regularly check these small components, such as replacing spark plugs or cleaning the throttle body every 20,000 kilometers to prevent issues. For safety reasons, prolonged shaking may lead to stalling or accidents, so it's best to have a professional shop inspect the electrical and fuel systems.
