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The mileage is about 100 thousand km, and the engine type is EA888's 2009 Volkswagen Skoda Hao Rui 1.8T manual block car. User response: engine idling of engine, abnormal noise of transmission. Check analysis: the common causes of engine jitter are the following 2 categories: one is the power imbalance of each engine cylinder, that is, the so-called "lack of cylinder", and the two is the mechanical vibration of the engine or the imbalance of the dynamic balance of the rotating parts. So I first check whether the engine is missing the cylinder. There is no combustion reaction in the cylinder, no matter whether the oil is cut off or the fire is broken, the temperature of the exhaust manifold of the cylinder will decrease. However, it was found that the temperature of each exhaust manifold was similar, and the problem of "missing cylinder" was not found. Then check the engine support connection, confirm the good no anomaly, the engine jitter should be due to the dynamic balance problem of the engine and power output rotating parts. Users reflect the vehicle engine idle jitter for a period of time after the abnormal transmission of transmission, I think there should be a correlation between the 2 failures, the transmission should be integrated to judge. After stepping on the clutch pedal, I carefully listen to the abnormal noise inside the gearbox. I judge that the axial or radial clearance of one axis or two axes is too large to cause the movement. The reference data found that the model engine used double mass flywheel. The source of the failure may be the loss of dynamic balance after the failure of the double mass flywheel, vibration and further impact on the work of the transmission. When the transmission is removed, the first axle front bearing (the crankshaft roller bearing) has been damaged, and the elastic damper of the double mass flywheel has also been damaged, and the clutch disc also touches the driven flywheel and appears scratches. At this point, the cause of the car's failure is identified. Because of the damage of the elastic damper of the double mass flywheel, the driven flywheel and the active flywheel can not be rotated concentrically, so the pressure plate and the driven flywheel are rubbed with each other, causing the entire flywheel to lose its dynamic balance and eventually lead to the engine jitter. At the same time, this also leads to the eccentric rotation of the transmission axis relative to the crankshaft, and then the shaft front bearing damage, causing the transmission often rodent gears to collide with each other to produce abnormal sound. Troubleshooting: replacement of dual mass flywheels, trial run after installation, jitter and abnormal noise.