Fault diagnosis of power shortage of Wuling vehicle
  • Automotive

A mileage of about 60 thousand km, equipped with type 462 engine, equipped with the 2006 generation Wuling car of the Delphi second generation MT20U EFI system. The car was trembling, lacking power, and accompanied by the failure of intake manifold tempering. Fault analysis: in general, in the case of refueling and shivering, the intake pipe is tempered, which indicates that the mixture is too thin, and the causes of excessive mixture are: low pressure of the fuel system, blockage of the filter net of the injector, the misalignment of the intake pressure sensor signal, and the misalignment of the oxygen sensor signal. Fault diagnosis: 1. first, use the fuel pressure gauge to measure the fuel pressure. The fuel pressure of the engine at idle speed and acceleration is 260 ~ 280kPa, normal. After the engine is extinguished, 20min can keep the pressure around 200kPa, and then the back of the oil pipe is stuck and the fuel pressure is raised to about 500kPa, and the power of the car is slightly better. Check the working conditions of each cylinder, carry out oil off and fire test, and find no cylinder failure. Cleaning the fuel injection screen of fuel injector still shows no signs of improvement. The X431 fault diagnosis instrument is used for fault detection, indicating that the system is working normally. 2. find the same type of engine ECU replacement test, normal driving about 1km, and then the same failure, then replaced back to the original car ECU, also can run about l km about L, and then the same failure phenomenon. This is not the engine ECU fault, but from the replacement of the engine ECU steps to analyze, because the replacement engine ECU first close the ignition switch, dismantle the battery of the iron line, so the original car engine ECU change, when the vehicle fails, the engine is extinguished, dismantling the battery line, after more than a dozen seconds after. Again, the normal driving around 1km. 3. when the fault occurs again, the X431 diagnosis instrument is used to detect the engine data flow: in the idle state, the intake manifold vacuum degree 50.2kPa, the throttle opening 0%, the throttle voltage 390mV, the coolant temperature 86 C, the engine speed 810r/min, the fuel injection pulse width 3.8ms, and the oxygen sensor output voltage 1127mV, the car has only 1 oxygen transmission lines. Sensilla). Moreover, the data flow of the oxygen sensor is 1127mV in both idle and accelerated state, and the normal change of the oxygen sensor should be within the range of 100 ~ 900mv, and the number of changes within the 10s is not less than 4~5 times, and the voltage of the oxygen sensor signal should be changed at about 450 + 50mV at idle speed. Acceleration test, step down the accelerator pedal to improve the engine speed from idle to 2600r/min, the intake manifold vacuum degree of 37.2kPa, throttle opening 6.5%, injection pulse width 3.0ms, acceleration engine shivering, surge phenomenon. The oxygen sensor connects the plug to the plug, so that the oxygen sensor works in the circuit breaker state, the vehicle accelerates normal, the oxygen sensor is replaced, the data flow is read again, the oxygen sensor data flow is changed between 114 and 870mV, the road test vehicle accelerates normal, and does not shake. Summary: 1. in the dismantling of the battery lift wire, stop more than ten seconds after the rest of the iron line, the vehicle runs normally, because the error signal of the oxygen sensor is stored in the random memory (RAM) of the ECU, when the battery is broken (off the B + line of ECU), the error signal of the oxygen sensor in the ECU (RAM) is deleted. Besides, the vehicle can run normally for a period of time. When ECU receives the error signal of the oxygen sensor again, the fault occurs again. 2. the fault point is that the signal given by the oxygen sensor is 1 high potential error signals, and the engine ECU receives the wrong signal and performs closed loop control, which makes the fuel injection to reduce the direction of the injection pulse width, and eventually causes the mixture to be too thin, which leads to the engine power shortage, the refueling trembling and the tempering phenomenon. 3. when the plug of the oxygen sensor is pulled out, the engine works under the control of open loop, the pulse width of the fuel injection is not regulated by the oxygen sensor, and the vehicle does not have the fault of insufficient power. 4. when using the engine fault detector, we can not simply read the fault code, but also read the data flow, compare with the correct data, find out the fault point. 5. when the engine fault indication of some vehicles is bright, the engine has trouble, the fault code can be detected by the diagnostic instrument. Some vehicle fault indicator lights are not bright, and the fault code is checked with the diagnostic instrument, but it can not indicate that the engine has no fault.