Why does the car shake when starting cold in winter but returns to normal after a while?
3 Answers
Winter cold start shaking that returns to normal after a while is caused by: 1. Low ignition energy: When the engine temperature is too low, both fuel and lubricant temperatures drop significantly. Cold starts require richer air-fuel mixture, which in turn demands higher ignition energy. Excessive spark plug gap can reduce ignition energy, causing engine shaking; 2. Incorrect air-fuel mixture ratio; 3. Uneven cylinder performance leading to engine vibration. Warming up is the first and most crucial step for winter driving. Due to low temperatures, lubricants become much more viscous than in other seasons and flow poorly. Warming up doesn't require waiting until the engine reaches optimal temperature - you can start driving once the temperature gauge needle begins to rise.
Having driven in the north for many years, cold start shaking in winter is quite common. Mainly because low temperatures make the engine oil too thick, leading to insufficient lubrication when the engine first starts, causing severe shaking. If the spark plugs are worn out, they are more likely to fail to ignite in cold weather, resulting in misfiring and shaking. Additionally, the fuel injectors may be clogged with carbon deposits, leading to poor atomization and uneven air-fuel mixture, which can also cause shaking. The ECU needs to adapt to the changes in air density at low temperatures; if it's not well-matched or the sensors are slow, the control lags. Generally, the shaking subsides after a while because the engine warms up, the oil thins out for smoother lubrication, and the system stabilizes. It's advisable to check the spark plugs and whether the oil viscosity is suitable for winter, and replace old parts promptly. Regular maintenance, especially a comprehensive check before winter, can help reduce such issues. I've seen many friends neglect this, only for the shaking to worsen over time, making repairs more troublesome. So early intervention is key—don’t let small issues turn into big ones.
I enjoy tinkering with technical details when it comes to my car. Cold start shaking in winter is often caused by sensor and ECU adjustment deviations. At low temperatures, the air flow meter or coolant sensor responds slowly, providing inaccurate data that misleads the ECU in calculating fuel injection, leading to an overly rich or lean air-fuel mixture and causing engine shaking. If the ignition coil is aged, unstable voltage during cold starts and weak sparks can exacerbate the issue. High oil viscosity is a common factor, as poor lubrication results in friction-induced vibrations. These issues typically normalize as the engine warms up because higher temperatures make sensors more responsive, the ECU self-learns to compensate, and oil fluidity improves. I recommend regularly cleaning the intake system, such as the throttle body, and checking for loose sensor connectors. Be cautious with vehicle modifications—for example, switching to winter-grade oil can help alleviate the problem. Pay attention to similar issues, like unstable idling, which often stems from the same causes. Use a diagnostic tool to read fault codes promptly; you don’t need professional jargon, as simple tools can help you perform preliminary troubleshooting yourself.
