The mileage is about 50 thousand km, the 2012 Audi Q5 equipped with CADA engine and OBK automatic transmission. User response: the engine has been shaking at idle speed. Inspection and analysis: maintenance personnel detect engine control unit and find fault indication of multi cylinder fire. In addition, there is also a fault code P2279 - there is a small amount of abnormal air flow in the intake system. According to the preliminary test results, there is a problem in the intake system. According to maintenance experience, this phenomenon is mostly caused by crankcase ventilation valve. After the crankcase ventilation valve is blocked on the manifold of the intake manifold, the engine is started, and the fault phenomenon is no longer found. Look at the fire related data, and all have returned to normal. However, when changing the crankcase ventilation valve, it is unconsciously found that there is a round cover in the valve chamber. Compared with maintenance data, it should be stuck at the end of the intake camshaft. After analyzing the reasons, it is considered that the crankcase ventilation valve is damaged, resulting in a large negative pressure in the crankcase. When the vehicle accelerates, the pressure in the crankcase will change abrupt, and the end cap will fall off the camshaft when it is impacted by the airstream. Troubleshooting: replace crankcase ventilation valve and intake camshaft end cover, trial run, engine data flow is restored.