Fault phenomenon
    A European BMW Model 316 sedan, the engine for the 164E1 type. Sometimes regardless of the cold car, idling will be between 1200-1500r / min beating; into the gear or open the air conditioning idle at 1500-1800r / min beating, sometimes very unstable.
    Check and repair
    1. Check the air flow meter: measuring 1 # 5V voltage, and 5 # feet and the engine computer common ground together; measure its 1 # and 3 feet between the feet of the resistance between 500 ohms, 2 # feet and 3 feet between the feet The resistance is 1360 ohms; measured 2 # pin signal line voltage, 1200-1500r / min when 2.33-2.47V, the voltage changes with the speed of the corresponding changes to accelerate to 2500r / min, the voltage is 2.7V, Are normal.
    2. Measure the resistance between the 4th # and 5 # feet of the air flowmeter, check the temperature sensor resistance, 2300 ohms at 20 ° C, 970 ohms at 50 ° C.
    3. Measure the resistance between the 12 # and 4 # feet of the engine computer, check the solar cell position resistance value, 1050 ohms at idle, 4320 ohms at full load, and measure the voltage value at full open - 1 when fully closed. 25-4.98V, no interruption, are normal.
    4. Measure the idle control valve waveform, the normal speed 800r / min, about 2s after the waveform is normal square wave, at 1200-1500r / min, at 12V to form a straight line. Test the idle control valve operating conditions are normal, the resistance value of 100 (normal 8 ± 2 ohms).
    5. Detection of oxygen sensor, the voltage between 0.4-0.45V, the change is very small, accelerated to 2500r / min after the voltage value of 0.55-0.58V, and the normal value of the change does not match. Oxygen sensor due to aging caused by poor work, replace the oxygen sensor, troubleshooting.