Symptom: a 2006 annual production of modern Tucson SUV, equipped with 2.7L engine, mileage of 145,000 km. According to the user to reflect the occasional acceleration of the vehicle will appear bad failure, and sometimes the engine will suddenly turn off.
    Check the analysis: Ask the user that the engine flame failure there is a certain law, the normal driving in the release of the accelerator pedal or red light when the number of occur more. If the engine is turned on immediately after the start is very difficult to start, only a few times to start or light step on the accelerator pedal can be a car. The user has replaced the idle valve and cleaned the throttle, each time after the repair symptoms will disappear, but soon after the same problem, the fault has not been completely ruled out.
    P0150 - Oxygen sensor signal stagnates in the state of mixed gas (1 row / sensor 1); P0123 - The sensor signal is stuck in the state of mixed gas (1 row / sensor 1); P0123 - Throttle / pedal position sensor circuit signal voltage is high. As the car has been repaired many times did not completely eliminate the fault, it can no longer rush to replace the accessories, maintenance personnel hope that through the road test to observe the engine real-time data flow to see if you can accurately find the point of failure. After clearing the fault code, check the engine data flow, lock a few key data for real-time observation, respectively, idling control valve duty cycle, throttle opening, throttle position sensor voltage, engine speed and actual speed, activated carbon tank electromagnetic Valve duty cycle, oxygen sensor voltage and intake air volume. Road test, in addition to speed up the weakness, the engine did not turn off, a few key data is no exception. Re-use the fault diagnosis device detection, display system is normal, there is no fault code. Is it an occasional fault? Since the user reflects the engine flame failure in the red light or release the accelerator pedal when the probability of higher, then it should focus on the simulation of these two conditions, in the event of failure to observe the data flow.
    Through the repeated test, the engine flame failure to reproduce, through the lock of several engine key data found abnormal situation. After a rapid acceleration, the driver's foot has left the accelerator pedal, the vehicle is in the sliding stage, but the data flow throttle opening has been shown as 34 °, throttle position sensor voltage is 1.7V, oxygen sensor voltage in the 0.6 ~ 0.8V between the slow changes. When the vehicle is almost stopped, the abnormality can be seen from the engine system data stream of the real vehicle. The throttle valve has been closed. The air is passed through the idle airway through the idling control valve. The vehicle actually works at idle. , But the data flow shows the throttle opening is 23.9 °, to the engine control unit ECM signal voltage is 1.3V, almost reached the full open 1/3. In this case, ECM to the actuator control signal will not follow the idle conditions, and this time the fuel injection pulse width of 15ms, while the normal idling pulse width of 2.5 ~ 6ms, the intake is not enough and fuel Too much, causing the mixture to be too thick, the engine will of course turn off. Sure enough, after a while, the engine will automatically turn off the fire. Do not step on the accelerator pedal in the case of many times can not start the car, light step on the accelerator pedal, the engine can be a smooth car.
    From the above maintenance process can be seen, obviously the throttle position sensor caused by the failure, it is in the engine idling conditions to provide ECM medium load error signal, so that the mixture is too thick, leading to engine flameout. At this point if the light step on the accelerator pedal, throttle open, the mixture was diluted, so easy to start.
    Troubleshooting: replace the throttle position sensor, the road test data flow are normal, turn off the phenomenon disappeared and accelerate the powerful, complete troubleshooting.
    Summary of the summary: the car's engine control unit, although the storage of the throttle position sensor fault code, but the single from the fault code to determine the throttle position sensor problem, it is too arbitrary, and the combination of data flow can be quickly and accurately Judge. Although the phenomenon of the car's fault is obvious, but because the data in the running is constantly changing, there is no standard data flow can be compared, it is difficult to naturally analyze whether the exception. In the idle conditions, there are standard data flow for reference comparison, but also in the idle speed there are obvious fault phenomena, so the use of idle data flow can quickly determine the point of failure.