The 2011 Buick Buick km cars with a mileage of about 31 thousand km. When the car is idle or running normally, the engine has a "dada" abnormal noise on the front part of the engine, and there is a sense of frustration. Fault diagnosis: after receiving the vehicle, test the car first and confirm that the fault is true. After inquiring the customer, the car had replaced the tension wheel and turbocharger because of this fault, but the trouble remained. Fault code is read by fault detector, and no fault code is stored. After careful consideration, the possible reasons for the failure are as follows: the vacuum tank rupture; the vacuum connection pipeline has the kink, the leakage or the installation; the turbocharger failure. When lifting the vehicle, when the engine speed is raised to 3000 r/min, the accelerator pedal is released quickly, and the abnormal noise is heard near the turbocharger. After dismantling the turbocharger inlet, it was found that the noise was transmitted from the inside of the turbocharger, because the turbocharger was just replaced, and the turbocharger was not damaged for the time being. Check the intake bypass electromagnetic valve near the turbocharger. It is found that the rupture of the vacuum tank results in a leak at the vacuum source. After changing the vacuum tank to test the car, the failure is still. GDS is used to drive the intake bypass solenoid valve and the exhaust bypass solenoid valve, all of which are normal and the pipelines are also normal. All the questions pointed to the turbocharger. When the turbocharger was prepared and tried to drive the turbocharger, it was found that there was a large vacuum suction when the vacuum tube was pulled out and the vacuum suction was not on the fault car. With this question in mind, the vacuum pipeline layout of the two cars was compared. It was found that the vacuum tank was reversed during the replacement process, and after re loading the vacuum tank, the trial run and the abnormal noise disappeared. However, there is a sense of setback when rapid acceleration, connecting fault detection instrument detection, found intermittent fire data, dismantling spark plug found that the ignition gap is too large, electrode burning is serious. After replacing the spark plug, test the car and troubleshooting.