Why does the Audi A6L shake when starting a cold car?

Q: The 2008 Audi A6L 2.0T fuel injector, spark plug, and ignition coil are all new. Why does it shake when starting a cold car?
A: If there is no problem when the car is hot, this situation will only occur when the car is cold. First, you need to check the carbon deposits, because the exhaust system of the 2.0T model is quite different from other models. The impact of carbon deposits on other models is very small, and the 2.0T model is more sensitive to carbon deposits. If the cold car shakes for about one minute when starting, and then the situation is normal, it can basically be judged that it is caused by carbon deposits.
Another situation is that the body does not shake, but the pulley in front of the engine shakes, which may be a fault of the generator pulley. The mechanism of the entire Audi series is relatively special. There is a one-way clutch in front of the generator. Once the clutch is damaged, it will cause the entire belt to vibrate. In this case, most repair shops will recommend replacing the entire generator assembly, which will cost about 8,000 yuan for the 2009 model. I recommend replacing the one-way clutch alone, which only costs more than 400 yuan in materials.