A Volkswagen Passat V6 2.8 L car with a mileage of about 65 thousand km in 2004. User response: the engine's idle speed jitter accelerates the phenomenon of powerless failure. The maximum speed can only reach 100 km/h. After receiving the car: using the fault detector to detect, the contents of the malfunction code retrieved show 1 cylinders, 2 cylinders, 3 cylinders are on fire and accidental. The idle state reads the data value, looks at the 1 cylinder, the 2 cylinder, the 3 cylinder's lack of fire condition, normal, in situ acceleration test, the breakdown phenomenon has not manifested. Road test, obviously accelerated weakness, and at the same time to check the data value, found that 1 cylinders, 2 cylinders, 3 cylinders serious fire. Because the car is V type engine, 1 cylinders, 2 cylinders, 3 cylinders on the right side, 4 cylinders, 5 cylinders, 6 cylinders on the left side. Failure for 1 cylinders, 2 cylinders, 3 cylinders at the same time fire, 3 cylinder spark plug, high pressure wire, ignition coil and other independent components can not be damaged and the same failure phenomenon, then the 1 cylinder, 2 cylinder, 3 cylinder shared parts damage. Check the gas distribution phase, normal. Test cylinder pressure of each cylinder, 1 cylinder, 2 cylinder, 3 cylinder pressure of about 8.5 bar (1 bar=100 kPa), 4 cylinder, 5 cylinder, 6 cylinder pressure of about 9.5 bar. It is obvious that the intake and exhaust system of the 1 cylinder, 2 cylinder and 3 cylinder has a problem. The intake manifold is removed and the variable intake manifold technology is used. The valve plate with the length of the regulating manifold in the intake manifold is not found to be stagnant and falling off. Since the intake system has no problem, it should be the problem of the exhaust system. The highest frequency and the most common fault in the exhaust system are three yuan catalytic converter blockage. Measuring the backpressure of 1 cylinder, 2 cylinder and 3 cylinder exhaust pipe is obviously larger than that of 4 cylinder, 5 cylinder and 6 cylinder exhaust pipe, and basically determines that the three element catalytic converter is blocked. Replace the 1 cylinder, 2 cylinder, 3 cylinder three yuan catalytic converter after road test, troubleshooting.