dfsk throttle valve repair case

     A Dongfeng Xiaokang minicar uses the United Electronics M7.8.0 system. The car had a fault with poor acceleration. When the accelerator pedal was stepped on, the engine surging after the engine speed exceeded 2000 r/min, the tachometer pointer oscillated repeatedly, and the speed no longer increased. The maximum speed of the car can only reach 50 km/h.

  

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  Start the engine, step on the accelerator pedal, and check the oil supply of the oil pump. The oil pressure is not abnormal, which indicates that the oil pump is working well. Because the speed is stable when idling or when accelerating below 2000r/min, it can be determined that the intake system has no leakage. Remove the main intake pipe, observe the cable between the accelerator pedal and the throttle valve and the throttle valve, all can work normally. In this case, check the throttle position sensor, turn off the ignition switch, and disconnect the throttle position sensor connector. It is found that there is a large amount of corrosion in the plug. After removing it with a brush, a terminal on the sensor is found That is, the ground terminal has been corroded and broken and left in the socket.

  

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  Check the sensor, as shown in Figure 1. Measure the throttle position sensor with the resistance file of a multimeter. Connect the two meter pens to the 1# and 2# pins. The measured resistance value is 2.4kO. The two meter pens are connected to the 2# and 3# rotary throttle. The resistance value changes with the opening of the throttle. The resistance value changes linearly, while the changes of l# and 3 support are opposite. The sensor is not damaged internally due to its good sealing. The cause of the failure is that the throttle position sensor ground connection column is open and no voltage signal is generated. Test drive after replacing the new throttle position sensor, troubleshooting.

  

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  It can be seen from the above cases that if the throttle position sensor or its related circuit is damaged, it will directly affect the acceleration performance of the engine, because when the engine ECU cannot receive the normal signal sent by the sensor, it will keep the engine running. Enabling the safety insurance function, relying on the data stored in the memory in advance, set the throttle position sensor signal to a fixed value, which cannot reflect the actual throttle opening. In this case, because the ECU cannot determine the load status based on the throttle signal parameters, the fuel injection volume cannot be set to a large extent to prevent damage to the engine and other components. At this time, even if the throttle opening is greater, the speed cannot be increased, and the optimal operating state of the engine cannot be maintained. At this time, the engine is actually in a fault state, and the self-diagnostic system also sends out an alarm at the same time, prompting timely maintenance.