What causes the Audi A4L to shake when cold?

[JayceLynn]

A4L cold shaking mainly has several major causes: carbon deposits, weak ignition, low cylinder pressure, unqualified fuel, etc. There are three main reasons for cold shaking: 1. Low ignition energy at low engine temperature: The temperature inside the engine is insufficient, and the temperature of both fuel and lubricating oil is not high enough; 2. Inappropriate engine mixture ratio: The air-fuel mixture ratio is not accurately adjusted, which exists in both open-loop and closed-loop control. In vehicles with closed-loop control, the minimum operating temperature of the oxygen sensor is 370 degrees Celsius. When starting the car, the temperature in the exhaust pipe does not reach 370 degrees Celsius, so the oxygen sensor does not work, leading to ECU misjudgment; 3. Carbon deposits on engine valves and intake ports: If carbon deposits occur on the engine valves and intake ports, they can absorb an appropriate amount of fuel, causing the ECU to make errors, resulting in shaking.