Why Does a Car Shake During Cold Start?

[McAxel]

Reasons for car shaking during cold start: 1. Improper air-fuel mixture ratio, inaccurate fuel-air mixture adjustment, which occurs in both open-loop and closed-loop control systems. In vehicles with closed-loop control, the oxygen sensor operates at a temperature of 370 degrees Celsius; 2. Carbon deposits on valves and intake ports. If carbon deposits form on the engine's valves and intake ports, they can absorb an appropriate amount of fuel, causing the ECU to make incorrect judgments; 3. Uneven cylinder conditions. After prolonged use of the engine, the gaps between each cylinder liner and piston may vary in size. Larger gaps in certain cylinders can lead to leakage of high-temperature gases, reducing power output; 4. Faulty coolant temperature sensor. If the engine's temperature during cold start is -10 degrees Celsius but the sensor reports a temperature of 20 degrees Celsius to the computer, the computer will inject fuel based on the 20-degree condition, resulting in insufficient fuel supply and causing shaking.

[OFinn]

My car shakes violently during cold starts, which is commonly caused by carbon deposits in the engine, stuck in the throttle body or fuel injectors, leading to uneven mixing of fuel and air. Worn-out spark plugs failing to ignite or faulty high-voltage ignition coils can also cause this. At low temperatures, the engine oil becomes thick, providing insufficient lubrication, making piston movement uneven. Don’t rush to drive; let the car warm up for three to five minutes, and it will run smoother. In severe cases, the throttle body needs cleaning, and new spark plugs should be replaced. Otherwise, fuel consumption will increase, and power will weaken over time. Regular maintenance checks on these components are essential.

[LeMarcus]

The cold start shaking I encountered mostly occurs in older vehicles, where the ECU computer system has adjustment deviations in cold weather, leading to an imbalance in the fuel-air mixture. Common causes include dirty air flow sensors or sticking throttle bodies. You can personally inspect the condition of the spark plugs and replace them if they are burnt out. It's recommended to clean the intake manifold carbon deposits every two years and use higher-quality engine oil to improve low-temperature fluidity. Don't underestimate the shaking, as it can accelerate engine wear.

[VonHenry]

The car vibrates and buzzes upon cold morning starts, not only creating loud noise but also affecting driving stability. The key is to promptly diagnose issues like excessive spark plug gaps causing insufficient ignition. Delaying repairs may lead to stalling while driving, posing safety risks. Visit a trusted repair shop to inspect the fuel injection system or fuel pump pressure - typically resolved through cleaning and part replacement. Always warm up the engine during cold weather before driving.