Symptom: A Santana 2000GLi sedan (equipped with an engine for the AFE EFI engine), the engine idling instability, the vehicle is running weak, and the urgent step on the accelerator pedal tempering, the engine serious jitter, relax the accelerator pedal Exhaust pipe is blasting.
    Fault check: VAG1552 fault reader to read the engine control system fault code, read the error code 00525-003, that is, no sensor oxygen sensor. Start the engine, use the VAG1552 fault reader to measure the data block function to read the data flow, see the oxygen sensor output signal voltage is 0.45V and always unchanged, indicating that the oxygen sensor has been damaged. Replace the oxygen sensor, clear the original fault code, although the error code 00525 disappeared, but the vehicle's original failure still exists. Read the fault code again 00561-015 that is more than the recommended value of the mixing ratio lower than the adjustment of the lower limit / SP (short period) and 00561-012 that the mixed ratio over the adjustment of the upper limit / SP (short period).
    Why do I still have this fault code after changing the oxygen sensor? With the doubt to clear the fault code, unplug the oxygen sensor wire plug and then re-read the fault code, the results of the fault code has disappeared. As the ECU is based on the oxygen sensor output signal to determine the combustible mixture of its mixed ratio, the reasons for the above situation is generally the intake manifold absolute pressure sensor, coolant temperature sensor, intake air temperature sensor, throttle position sensor work Bad or fuel pressure instability, then, with a fuel pressure gauge fuel system fuel pressure measurement, the results of normal fuel pressure; with the oscilloscope to measure the injector fuel injection pulse width of 4ms, also in line with the car maintenance manual technical requirements, thus Excluding the possibility of several of the above-mentioned sensor failure.
    In the removal of the spark plug to check, found that the spark plug electrode has a lot of brown like moldy carbon deposition, so remove the injector to check the fuel injection and found that the injector fuel is not only not atomized, but also linear , And when the big and small, with the ultrasonic fuel injectors after cleaning check, fuel injector fuel injection situation is still no improvement, thus determining the injector has been damaged. Replacement of a new injector for commissioning, the engine idling smoothly, remove the fault code and then re-read the fault code, then the two fault code also disappeared, but the engine is still accelerated when the jitter. Finally, with the oscilloscope to detect the ignition system secondary ignition waveform, found that the secondary ignition waveform is inverted; see the line no exception, try to plug the primary line of the positive and negative, and then use the oscilloscope to check the secondary ignition waveform, Although the ignition waveform is no longer inverted at this time, but found 1,3 cylinder ignition secondary waveform shows the ignition breakdown voltage of about 25kV. Unplug the high voltage line with a multimeter resistance file to measure its resistance value ∞. Replacement of a group of high-voltage line after the test, the engine work back to normal, complete troubleshooting.
    Failure analysis: Although the car's fault phenomenon is not unique, but the cause of the fault is more complex, and is comprehensive. Mixing ratio is due to the fuel injector needle stuck and lost the atomization function, resulting in the mixture into the cylinder is not normal, burning deterioration, the engine will work instability, and the emergence of tempering, blasting phenomenon; , The negative pole is wrong, the engine can start, but the engine power is reduced, it is because the spark plug work center electrode temperature is higher than the side electrode, high voltage from the center electrode to the side of the electrode movement is relatively easy, in the direction of the distributor It is not only the ignition waveform inversion, and the direction of electronic movement is just the opposite, the ignition energy consumption will increase; with high voltage sub-line resistance is too large (open circuit), too much consumption of high pressure Energy, the end of the spark plug flash is not normal and the above failure.