Why does the Audi A6L shake during cold start?

[LailaDella]

Audi A6L cold idle shaking has the following three reasons: 1. The temperature inside the engine is insufficient, and the temperature of both fuel and lubricating oil is too low. 2. Uneven cylinder pressure, excessive carbon deposits on intake valves and intake pipes. 3. Fuel injection issues caused by excessive internal carbon deposits in the nozzles. 4. When the water temperature is low, it is considered a cold start, and the engine noise is very loud, especially in winter, sounding like a tractor with significant vibrations, which improves when the engine warms up. This is a normal phenomenon because combustion and lubrication are poor during cold starts. The engine runs at higher RPM when cold and lower RPM when warm, leading to incomplete combustion which can cause carbon buildup, blackened exhaust pipes, and in some cases, blue smoke for the first few seconds, indicating oil burning, which is also normal.