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Fault phenomenon: a 2001 style Nissan wind A33 car, VQ20DE 2.0L V6 engine, RE4F04B four speed automatic transmission, the car has been driving 250 thousand kilometers, can be scrapped car, the owner described: the car recently high fuel consumption, the engine in the process of the occasional failure to extinguish the engine, but restarted again It can work normally. The frequency of flameout can sometimes be 2~3 times a day, sometimes not for a few days, but almost two days. Fault diagnosis: to test the car, run smoothly, open the air conditioning speed is good, rapid fire throttle speed increase faster, but slow step on the throttle, the engine in 2500~3000r/min between the car phenomenon, engine fault lights can also be normally extinguished. Carry out road test, speed up performance is good, automatic transmission jumps smoothly and coherently. So let the engine keep 2000r/min 10min, a loose pedal, the engine automatically flameout. Because only the test lights and multimeter, it is impossible to read the data flow under various working conditions of the engine. Before restarting, manual code reading is used to read whether the engine control unit (ECM) has fault code storage. The vehicle uses a OBD-II diagnostic joint. The ignition switch ON, the 1# foot of the diagnosis seat and the 8# foot, wait for the 2s to open the cross connection. At this time the system starts to flicker, and the four digits of the engine fault light are observed, and the four digits are the result of the system detection. Through manual code reading, the fault lamp is displayed brightly, indicating that the system has no fault memory. Using the multimeter to test the resistance of the water temperature sensor, the normal temperature state is 2.4k omega (standard value 2.1~2.9k omega); the water heater is heated in the water heater, the resistance value drops steadily, the resistance value is 0.24k omega (standard value 0.23~0.26k omega) when the water temperature reaches 90. By measuring its two signal lines, the yellow line of the 70# foot of ECM has 4.9V voltage output, the black input line of the 58# foot is well connected with the water temperature sensor, and there is no problem in the water temperature signal, and the engine can basically be excluded from the water temperature caused by the engine. The top three spark plugs are removed, and the spark plug electrodes are black, which is obviously caused by poor combustion. A pair of original plant spark plugs were replaced, and six injectors were cleaned and tested, the throttle body was cleaned and the gasoline filter was replaced (installed with the oil pump). The oil pressure meter was restarted and the test was simulated. After a long time, the fault still appeared, but the oil pressure was kept on the oil pressure meter. Standard pressure at 275~314kPa. After analysis, the fault is in the air flow meter. Then test the signal of air flow, the four connecting lines are red / green line 12V power, red line 4.9V power, the black line is ECM internal grounding wire, the white line is the signal line, the line has 1.6V voltage at idle speed, accelerates to 2000r/min, the signal voltage is as high as 2.3V, and normal idling signal is below 1.3V, acceleration to 2000r/min is not It can exceed 2.1V. It is preliminarily determined that the fault is caused by the deviation of the air flowmeter signal. Troubleshooting: Troubleshooting after changing the air flowmeter.