What Causes Severe Vibration When Starting a Car?

[McSimon]

Severe vibration when starting a car can be attributed to the following reasons: 1. Faulty coolant temperature sensor: The coolant temperature sensor is one of the key parameters for the ECU to determine engine operating conditions. If the engine starts cold at -10°C, but the sensor "tells" the ECU "the current temperature is 10°C", then the ECU will inject fuel based on the 10°C operating condition, resulting in insufficient fuel injection and causing vibration. 2. Carbon buildup on valves and intake ports: Since carbon deposits have excellent adsorption properties, when severe carbon buildup occurs on intake/exhaust valves and intake ports, the fuel injected by manifold-injected engines will be partially absorbed by the carbon deposits. This creates a discrepancy between the actual fuel entering the cylinders and the ECU's preset values, causing the energy released after combustion of the air-fuel mixture to fall short of power requirements, leading to vibration.