What is the reason of normal jitter when Audi a5 cold car starts?

The normal causes of shaking of Audi a5 cold car are low temperature and insufficient temperature in the engine, so it is necessary to inject more fuel to meet the power demand when starting the cold car. The larger the gap between spark plugs, the smaller the ignition energy. The fuel atomization is not good at low temperature, and the fuel needs high ignition energy, which affects the power performance and makes the car shake. The reasons for idling jitter of cold cars are as follows: 1. Mechanical failure of engine. For example, the pressure of each cylinder is uneven; 2. Air intake system failure, such as air leakage in the air intake pipe. Excessive carbon deposition in the intake valve and intake pipe, excessive dirt on the inner wall of throttle valve and intake pipe, etc. 3. Engine management system failure. For example, incorrect water temperature and intake air temperature signals, line faults, etc. ; 4. There is something wrong with the ignition system. For example, the spark plug has too much carbon deposit or incorrect gap, the high-voltage line and distributor cover leak, and the ignition coil is damaged. 5. Oil supply system failure. For example, when injecting oil, the nozzle is not closed tightly or blocked due to too much colloidal carbon deposition inside the nozzle.