What Causes Severe Engine Shaking During Startup?

[PiperLynn]

Severe engine shaking during startup can be attributed to the following specific reasons: 1. Excessive carbon buildup in the throttle body, fuel injectors, or intake passages may be one of the causes. 2. When there is too much carbon deposit inside the engine, the gasoline sprayed by the cold-start injector can be largely absorbed by the carbon deposits, resulting in an excessively lean air-fuel mixture during cold starts and causing startup shaking. 3. Mechanical failures in components such as ignition coils, spark plugs, or fuel injectors, leading to cylinder misfires; low fuel pressure or cylinder pressure, resulting in insufficient power. 4. Oxidized or low-grade engine oil, primarily due to poor low-temperature fluidity, leading to inadequate cold-start protection for the engine.