What Are the Causes of Idle Vibration During Cold Start?

[VonIsabel]

Reasons for idle vibration during cold start: 1. Excessive carbon deposits in the engine, dirty throttle body, or excessive carbon buildup in the fuel injectors, leading to an overly lean air-fuel mixture during cold start and making it difficult to start; 2. Issues with the ignition system—after prolonged use, the spark plug's ignition gap and timing control may vary, but the ECU cannot detect this deviation, resulting in some cylinders producing less power and causing vibration; 3. After extended engine use, the clearance between each cylinder liner and piston may vary, and without proper oil lubrication during cold start, larger clearances allow some high-temperature gases to leak, reducing power output; 4. Unstable fuel pressure; 5. Faulty coolant temperature sensor—when it fails, the ECU cannot receive the signal to provide a richer air-fuel mixture and can only supply a leaner mixture to the engine.