The mileage is about 14 thousand km Yutong Bus. Customer Description: when the speed of the vehicle is between 90 krn/h and 100 km/h, the noise inside the train is relatively large, and passengers have dizziness and vomiting for a long time. The customer reflected that the car was generally running in the city, the speed was low, the stroke was short, the fault was not found, and the vehicle was found on a highway about 6000 km before it was found. Because the fault has been repaired several times, the differential assembly and transmission shaft have been replaced separately, and the trouble has not been completely eliminated. Fault diagnosis: first, according to the fault phenomenon reflected by the customer, the road test is carried out to confirm that the fault is true. According to the failure phenomenon and the test result analysis, the possible causes are as follows: the running parts of the vehicle are not balanced; the bus body and the chassis are loosened; the transmission system of the chassis is loose; the tilt coordination between the chassis components is error; the engine's power output is insufficient when the engine is running at high speed. First, check the engine's working condition at idle speed, medium speed, high speed and quick acceleration. There is no jitter or acceleration. Then check the connection between the body and chassis, and the chassis transmission system is not loose. Disassembly and installation of transmission shaft, the tire after the action balance test after trial run, the fault still exists. In the end, the tilt angle of the engine assembly, the transmission assembly and the rear axle assembly is measured by the electronic angle tester. It is found that there is a certain error between the angle and the angle of the three assembly parts. When the angle is adjusted to the appropriate position, the related data are recorded and the standard adjustment gasket is used. Whole. After adjusting the angle of the engine assembly, the transmission assembly and the rear axle assembly, it is found that the engine speed is more than 90km/h, and the engine has a slight vibration in the rapid acceleration compartment. It has been learned that the car was produced in October 2013, and the maximum driving speed of the bus must not exceed 100 km/h. When the engine ECU detects that the speed exceeds 100 km/h, the engine ECU will control the engine fuel injection and limit the torque output to control the speed. However, the actual speed of the vehicle did not reach the specified value of the speed limit, and it began to limit the output of the engine torque, so it was identified as a problem in the ECU control procedure of the engine. Contact the engine manufacturer to modify the relevant data of the vehicle engine ECU, and then test the vehicle thoroughly.