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The handling of the idle speed of idling accelerated the weakness of a 230000km Santana 2000GSi car, equipped with a AJR engine, and a BOSCHM3.8.2 electronically controlled multi point fuel injection system. The car was overhauled at other repair plants three months ago. During the running in period, it was found that the car was somewhat shaking when the cold car just started the car. After the repairman checked, it said that the car would be ready after running in. But with the use of the car, the fault is more obvious, and there are symptoms of rapid acceleration. Now, after the cold car starts the car, the idle jitter is very strong, the speed is only 500r / min, and sometimes it will automatically extinguish. Back to the repair factory for two days, the cylinder line, the spark plug, the oxygen sensor and the air flow sensor have been replaced successively. The throttle has been cleaned and the fault has not been obviously improved. Try it! After the car, first do basic inspection did not find abnormal, connect the fault diagnosis instrument, open the ignition switch. Enter the engine electronic control system, inquire the fault record, found the record has three fault codes. Respectively: 00533 idle speed adjustment exceeds the adaptive limit; 0066830 line electric voltage is too low SP. After the fault code is cleared, the throttle control unit is matched with the "basic setting function". After the match is successful, the system is withdrawn. The car found that the idle speed was still jitter. Re entering the system to inquire the fault code showed that the system was normal. No trouble record. Using "measuring data block function" to read engine data flow, there are several groups of data engine speed 700R / min, throttle opening 20. ignition advance angle 4 to 8 degrees, water temperature 85 degrees, air inlet temperature 34 degrees, engine load 2.2ms (injection pulse width). Intake volume 3.1g / s. oxygen sensor electrical pressure 0.1 to 0.2V, fuel adjustment 25 %. The above data show that the fuel mixture is too thin and the fuel adjustment has reached the limit. According to data analysis, fuel injection pressure may be low. Fuel injector is blocked or air inlet pipe has air leakage. Check the air leakage position in the inlet pipe. Connect the fuel pressure gauge to measure the fuel pressure. The oil pressure at the idle speed is about 240kPa. The vacuum tube on the oil pressure regulator is pulled up to 300kPa. After closing the ignition switch. The oil pressure can be maintained at about 200kPa 10min., which basically can tell that the fuel system is supplied normally. In the process of checking, we found intermittent shivering. With the data flow observation, it is found that the fuel adjustment is about 6%, the oxygen sensor voltage is O.2 to O.7V, the speed of the accelerator pedal is drastically jitter, the oxygen sensor voltage jump to 0.1V, and the idle speed is steadily stabilized after about O.5min. The fuel adjustment reaches 25%, the basic setting function is used. The input 099 is closed to the oxygen regulation. The idle jitter is serious. When the fuel pressure is high to 350kPa, the idle speed is stable and the values tend to be stable, but the angle of the throttle is changed to 0. The analysis should be caused by the leakage of the intake pipe after the throttle, and the pipeline of the carbon tank and the brake vacuum pump should be broken in turn, and no obvious reaction is found. A carburetor cleaning agent is used to spray the root of the injector gently. When the root of the 3 cylinder and the 4 cylinder is ejected, the engine speed is obviously fluctuated and the 3 and 4 cylinder injector is removed. The seals of the two injectors have been distorted and aging and cracking. After replacing the sealing ring of the 4 injectors, the engine idling is stable, and the data streams return to normal. When the car was overhauled, the repairman did not change the seal ring in accordance with the regulations, and the operation was improper, and the sealing ring was twisted and loaded. At first it was just a slight leak and the failure was not obvious. But with the use of the car, the bad environment (high temperature, shock) in the sealing ring caused the failure more serious and brought to the owner. There's no need for trouble. Remind colleagues here. In the maintenance process, we must strictly operate according to the requirements, which not only reduces the trouble to others, but also improves their reputation. The leakage of intake pipe is different for different control modes and different leakage locations. When judging this kind of fault, we should analyze the data scientifically and flexibly according to the control principle, so as to find out the location of the fault quickly and accurately. Condition: engine computer should be supported by idle speed adjustment function. (someone will ask Shanghai Santana 2000 to tune it? ). The engine computer system has no trouble memory. After the engine is running, the cooling fan will stop after the first action (to ensure that the water temperature condition reaches), the intake pipe and the valve cover do not leak steam, the ignition is normal, and the high voltage line is intact. The cylinder pressure is at normal value and the overhaul engine must be correct. Note: for the engine computer that needs the password to adjust to the idle speed, you must first enter the correct 5 bit password in the 11- login to select the European car system to enter the Audi selection engine system. [01- engine][10- adjustment and / match] input channel number: 01 screen shows the current value ---128---- input desired modification value adjustment range can only be (lower 124 to upper limit 132, roughly 750 to 850r/min) [save modification value] again to adjust the input 001 channel to see if the front value is not the current modification value is (exit) [06, exit]