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The mileage is about 89 thousand km, the 1. 4L engine and the manual transmission 2006 Volkswagen Polo car. Customer response: the engine sometimes stalls while driving. Inspection and analysis: according to the customer description of the failure phenomenon, the car fault is accidental, first of the engine control unit fault query, after the query did not appear fault code, to see the engine idle speed of the data are normal. Consider that if the engine mixture is too low due to low fuel pressure, the short term fuel correction will approach or reach +25%. Next, wait for the engine to stall through the road test to see if there is a big change in the short-term fuel correction of the engine. Start the engine, connect the vehicle diagnosmeter into the engine control unit, choose to read the measurement data block function, and view the short-term fuel correction value of the third display area of the display group 001. After a long trial run, the fault finally appeared, stepped on the accelerator pedal, and the engine speed did not respond, followed by the engine shaking and finally flameout. The short-term fuel correction on the vehicle diagnosis instrument has reached + 25%, and the reboot engine to view the short-term fuel correction value is around 0%, which indicates that the cause of the quenching is that the engine mixture is too thin. Then check the fuel pressure is normal, after the measurement of the idle speed of fuel pressure is 4. 0bar, instantaneous step down the accelerator pedal, fuel pressure close to 4. 0bar, which indicates that the fuel pressure is normal. As the engine is not malfunctioning, the oil pressure is normal, but it does not mean that the fuel pressure is normal when the engine fails. Based on past experience in maintenance, it is preliminarily determined that the cause of the extinction of the mixture is mostly due to the damage of the fuel pump. After the replacement of the fuel pump, there was no failure in the long time trial run. After a week's visit, the customer failed to respond. Summary and analysis: check engine failure. If there is no fault code, check the changes of short-term fuel correction when failure, and analyze the failure.