Nissan Fuga car idling unstable

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Symptom: a Nissan Fuga car in the shop after I cleaned the air intake and fuel systems, engine electronic control unit can not complete the idle air volume self-learning, long-term fuel correction factor is cleared, you can successfully complete the Idle Air Volume self-learning but when the engine is idling shaking intermittently, other conditions are normal.         Failure Analysis: With CONSULT-II detector test, the system of no fault code is stored. View the data stream and found two air-fuel ratio sensor signal voltages are high (standard value at 1.5 V). When the air-fuel ratio feedback signal voltage rises to 1.9 V or more, fuel injection pulse width will suddenly increase, then the engine will follow jitter, followed by air-fuel ratio feedback signal voltage lexia 3 starts to drop down to 1.6 V or so when , fuel injection pulse width returned to normal, the situation has returned to normal engine idling. Combined effect of air-fuel ratio sensor according to the fault phenomenon, analysts believe that the engine idle shake is caused due to fuel ratio feedback control. But what factors are causing the high air-fuel ratio sensor signal voltage it? Because air-fuel ratio feedback control is normal, you can basically rule out the possibility sensor or wiring problems. Further analysis, that the car may be too lean mixture, resulting in air-fuel ratio sensor signal voltage is too high. References maintenance data, can cause the mixture too lean causes are: air intake system vacuum leak; PCV valve damage; air flow sensor is faulty; injector clogging.         First check the working condition of PCV valve and found no abnormalities. Vacuum table intake leak check, nor abnormal. Observation data stream air flow sensor, within the normal range. This leaves the injector did not check this one, although the fuel system has been cleaned, but still decided to remove the fuel injector to check. Examination found near some dirty injectors, so once again carried out a purge, after the test found that the fault persists.         At this point the maintenance impasse. After careful analysis, or the need to re-check the air flow sensor, air flow sensor signal Tuirel S777 voltage because although there is no obvious abnormalities, but completely beneath quasi possibility of misalignment of the signal on the air-fuel ratio sensor signal is amplified and revealed. To verify this speculation, and got an air flow sensor test and found that the air flow sensor signal voltage at the engine speed is higher than the original 700 r / rain 0.04 V or so, and the failure disappears.         Troubleshooting: So the air flow sensor removed, carefully observed in the sunlight, found the hot wire air flow sensor on the side where there half a fly head stuck inside, resulting in reducing the amount of air flowing through the hot wire, resulting in air flow sensor signal voltage is low. After clearing the air flow sensor foreign body inside the failure to completely ruled out.