【Fault description】
    The exhaust color is black when no load is accelerated.
    【Inspection process】
    The CO and HC concentrations at the time of idling were measured. As a result, CO was 11% and HC was 2200 ppm (1 ppm = 10-6). The fuel supply for this vehicle is the KE-Jetronic system, which is mechanically controlled, and various incremental and reduced injection compensation are electronically controlled. It is first suspected that the compensation control in the electronically controlled hydraulic actuator is malfunctioning, thus pulling down the electronically controlled hydraulic actuator connector. That is, artificial production does not compensate for the effect. As a result, the concentration of CO in the exhaust gas was reduced to 3.5%. In this state no load acceleration, there is no black smoke in the exhaust. From this test the results can be analyzed for some reason that causes the system to perform fuel incremental compensation for jetting.
    【Fault Analysis】
    For the incremental compensation jet, the water temperature sensor has the greatest degree of influence, and the result of the resistance is 300Ω, there is no problem. Second, check the oxygen sensor, searched the engine room, and did not find something like an oxygen sensor. So the car lifted up along the exhaust pipe to find, the results found that the oxygen sensor installed in the central part of the floor. Connect the voltmeter to the connector, resulting in a voltage of only 0.3V and no change at all. From the idle emissions of CO emissions analysis, the oxygen sensor output signal voltage should be more than 0.5V Caixing. Unplug the oxygen sensor connector, that is, cut off the oxygen sensor feedback control, the results of the exhaust CO content decreased. From this result can be analyzed, exhaust gas CO and HC concentration is too high by the oxygen sensor.
    With the dry battery instead of oxygen sensor output combustible mixture air-fuel ratio over-thick signal, CO concentration dropped to 0.1%, confirm the control system function is normal. Replacement of a new oxygen sensor, air-fuel ratio feedback that can play a normal role, acceleration does not produce black smoke.
    Therefore, as long as the engine running state no change, fuel consumption more up, then the oxygen sensor is to check one of the important components.