Fault phenomenon
    A Santana 2000GLi sedan, the car has been running 380,000 km. The recent emergence of idle instability of the fault, after several times to find and debug failed to rule out.
    Troubleshooting and troubleshooting
    Because this failure involves a wide range, need to carry out a number of testing and testing, but to seize the main contradiction. First of all from the appearance of the lines and vacuum tube and intake pipe to check, no exception. According to maintenance experience, the car is most likely to idle instability is the oil system is faulty, first check the hydraulic regulator function is normal. (The standard value should be 0.20MPa); then unplug the vacuum tube, the measured pressure is less than 0.2MPa (fuel pressure should be 0.35MPa), the pressure of the oil system is about 0.15MPa, the fuel pressure is about 0.125MPa, , Indicating that the hydraulic regulator function failure, can not maintain the oil pressure in a variety of conditions remain unchanged. So get a similar type of hydraulic regulator for the fault on the car, the fire test, the fault disappears.
    Failure analysis
    The function of the oil pressure regulator is to keep the pressure difference between the fuel pressure and the inlet pressure constant, so that the fuel injected into the injector depends only on the valve opening time. When the oil pressure regulator is faulty or damaged, the actual fuel injection quantity is changed due to the fluctuation of the intake pipe pressure, although the fuel injection indication given by the engine electronic control unit is correct.