A Volkswagen Passat driving car with a mileage of about 120 thousand km, equipped with BGC engine and 01V type 5 stop manual transmission. BGC Users reflect: the car idling instability, change into the forward gear, the engine will appear the trend of flameout, the need to step down the accelerator pedal to start many times, otherwise it will be extinguished. Inspection and analysis: maintenance personnel connect VAS5052 fault diagnosis instrument to inquire engine, trouble free information. When the engine is running at idle speed, the data flow is read. The rotational speed is 800 r/min, the engine's relative load is 34.8%, the coolant temperature is 95 C, the intake volume is 5.2 g/s, the throttle angle is 4.8%, the actual value 0.80 ~ 0.82, the target value 1, the short-term fuel correction 25.1%, the front oxygen sensor voltage 0.620 ~ 1.120 V. These dynamic data clearly indicate the current idle mixture concentration. When the engine is self extinguishing in the inspection, after starting again and stabilizing the idle speed, a fault code 17705 - the pressure between the turbocharger and the throttle is reduced and static. Read the data stream again. The rotational speed is 760 r/min, the relative load is 21.8%, the coolant temperature is 95 C, the intake volume is 5.2 g/s, the actual value is 1.03 ~ 1.04, the target value 1, the short-term fuel correction 25% and the voltage of the front oxygen sensor 1.620 V, the data show that the state of the mixture gas is thinning at this time. Check the intake hoses between the turbocharger and the intercooler and remove them according to the fault indication. Troubleshooting: reconnect hose and troubleshooting. In the action of the counterforce, the front end of the engine is upwards, and the front end of the engine will sink when the R is on E. The trend of vehicle acceleration and deceleration still exists. When the hose connection is loose, the intake pipe is slightly leaked. Because the pressure in the inlet pipe is higher than the atmospheric pressure, the leakage direction of the air flow is from the inside to the outside. This part of the air leakage has passed the measurement of the air flow meter. The control unit determines the basic fuel injection according to the measurement value, but there is not so much air entering the cylinder, so the mixture is in a strong state. After the flameout is shut down, the hose is removed, the gas leakage measurement is large, the pressure in the intake pipe drops: the outside air is entered from the outside, the measurement value is small and the air in the cylinder is more, so the mixture gas is in a dilute state. When the intake pipe pressure is reduced to a certain value and the fault code generation condition is met, the control unit stores 17705 of the memory.