Why does the Citroen C4L engine shake when cold?

[Luna]

Here are the main reasons for engine shaking during cold starts: 1. Excessive carbon buildup in the throttle body, fuel injectors, or intake manifold - it could be one of these or all of them. 2. When there's too much carbon buildup inside the engine, the gasoline sprayed by the cold start injector gets largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture during cold starts and causing shaking. 3. Mechanical failures in components like ignition coils, spark plugs, or fuel injectors leading to cylinder misfires. 4. Low fuel pressure or cylinder compression causing insufficient power. 5. Substandard fuel quality. 6. Damaged or excessively dirty idle control valve. 7. Intake manifold leaks. 8. Damaged engine mounts or cushion pads. 9. Oxidized or low-grade engine oil, primarily with poor low-temperature fluidity, leading to inadequate engine protection during cold starts.