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A driving mileage of about 235 thousand km, the assembly of South Korea's modern G4JS.2.4L DOHC 16 valve multi point injection electronically controlled gasoline engine, the 5 speed manual transmission of the 2004 Jianghuai Rui commercial car because of the speed of acceleration weak, high oil consumption in the factory maintenance. Fault diagnosis: communicate with the owner of the car. Due to engine oil burning signs and acceleration, the car can only run to 100km/h at flat speed. The engine of the car has been overhauled recently in a steam repair shop, and the spark plug, the shedding line, the ignition coil, the crankshaft position sensor and other parts have been replaced. The phenomenon of oil burning has been solved, but the symptoms of acceleration are still existing. The possible factors that cause the electric control gasoline engine to speed up weak and high fuel consumption are: the brake system brake clearance is too small or the brake clearance is too small, the fuel system has dirty plugging, the fuel quality is bad, the air flow sensor and its line fault, the oxygen sensor fault, the intake pressure sensor and its line fault, crankshaft Position sensor and its line fault, camshaft position sensor and its line fault, spark plug work bad, ignition coil and cylinder line aging phenomenon, engine mechanical failure (cylinder pressure is insufficient), intake and exhaust system blocking phenomenon, engine ECU failure and so on. After taking the car, the engine of the car has been replaced by the ignition coil, the spark plug and other parts in the course of the overhaul. The read out fault code is P0100, and the air flow sensor circuit is faulty. After the code was cleared, the fault code disappeared. Read the engine idle speed data flow, oxygen sensor signal voltage: 0 to 900mv change, air flow sensor: 285 to 310mV change, intake temperature: 27 degrees, throttle position sensor: 293mV, coolant temperature sensor 62 degrees, engine speed: 874 to 906r /min change, injection duration: 2.8 To 3.1ms transformation, the engine load is: 26.9%, ignition timing: BTDC 6.5 ~ 9.5 degree change, ISC actuator duty ratio: 46%, air fuel ratio closed loop: CLOSLOOP, B1 ~ 4.7%, short-term fuel: - B1 ~ 3.9%. The engine runs continuously for about 15min, and the coolant temperature reaches 73 degrees Celsius. Why does the coolant in the car don't come up at temperature? Does the car's thermostat make "hands and feet" artificially? It was doubtful, so the engine was extinguished and the thermostat was removed to check. After dismantling, it was found that the thermostat had made two holes around No. 6. After negotiation with the owner, a new thermostat was replaced, the car was checked further, the new heater was finished, the engine was started to start the car and let it idle. After running, about 10min, coolant temperature has reached the normal working temperature (88~93 degrees Celsius). At this time, again check the engine idle speed data flow, the data recovery normal, oxygen sensor signal voltage: 0 ~ 900mv, air flow sensor: 261 ~ 273mV, intake temperature: 31 degrees, throttle position sensor: 278mv, coolant temperature sensor 91 degrees, motive speed: 749.9r/min, injection continuous time Room: 2.3 ~ 2.6ms, engine load 17.8%, ignition timing: BTD C 6.5 ~ 8.5 degrees, ISC actuator duty ratio: 37.6%, air fuel ratio closed loop: CLOSLOOP, long-term fuel, short term fuel within 10% of the man. Through data flow observation, it is almost certain that the engine electronic control system has no problem. Then, the car is taken up by the lift, then the engine is started and the shift lever is hung in the 5 gear. The car carries out the non load and empty load test. With the increase of the throttle's opening, the speed of the car can increase obviously. The engine does not feel the engine power shortage when the test is empty; the engine is used to test the engine with the fault cylinder. There is no abnormality in the test. Suspect that the vehicle exhaust system three yuan catalytic converter may be blocked, but the owner repeatedly stressed that the car three yuan catalytic converter has been checked in other car repair shop. After the removal, there was a blockage. It had been treated as "through". The three yuan catalyst should not be blocked. The car owner suspects that the oil pressure of the fuel pump may cause the engine to speed up weakness in the driving. According to the wishes of the owner, the fuel pressure of the car is tested first. When the engine is running at idle speed, the readings of the oil pressure meter are about 300kPa, and the readings of the oil pressure meter can rise to 350kPa when the speed is speeded up, indicating that the fuel pressure of the fuel pump is normal. The cylinder pressure is tested, and the cylinder pressure of each cylinder can reach 1100kPa, indicating that there is no problem in the internal mechanical aspects of the engine. After the corresponding test, the car carried out the road test, still feel the engine acceleration weak, through the corresponding inspection, measurement, and failed to find out the real reason for the engine acceleration weakness, when the troubleshooting in doubt, suddenly remembered whether the car installed the three yuan accelerator, so that the vehicle is lifted again. The exhaust system was checked by the machine, and it was found that the exhaust system of the car was equipped with a three yuan catalyst, and the latter three yuan catalyst was removed and checked and found to have been seriously blocked. Troubleshooting: after the agreement with the owner of the car, the replacement of a new three yuan catalytic converter loading, through repeated road test, the car acceleration weakness, high oil consumption failure completely eliminated. Fault summary: the fault is mainly caused by the three element catalytic converter blocking after the exhaust system. Because the vehicle emission standard is the national II standard, it is easy for the maintenance personnel to ignore the inspection of the three - element catalytic converter after the failure. Friendship and connection: with the progress of the society and the attention of the state to environmental protection, the relevant regulations have also been formulated for the emission standards of automobiles. China has implemented the national III emission regulations in the country since July 1, 2008, that is to say, the standard of automobile emission produced after July 1, 2008 must reach the national standard of III, and after 2010. The emission standard of the electronically controlled gasoline engine must reach the IV standard of the country. Then, some of the emission standards of the electronic control gasoline engine produced before July 1, 2008 can reach the national III standard, and many vehicle emission standards can only reach the national standard of II, so most auto manufacturers have only one installed on the vehicle of the national II emission standard. The oxygen sensor and three element catalytic converter are used to detect the oxygen content in the exhaust gas. The engine ECU is based on the data collected by the oxygen sensor to control the air fuel ratio of the engine, and the three element catalytic converter is used to purify the exhaust gas and reduce the pollution to the atmosphere. Then, the front and rear oxygen sensors and the front and rear three element catalytic converters are generally installed on the III and IV emission standard gasoline engines. Here, with the help of your journal, remind colleagues to pay attention to the three yuan catalytic converter before and after repair of similar vehicles. According to the relative calculation, the emission of particulate matter in the III phase and the I phase of the country decreased by 70%, and the NOx emission decreased by 39%; compared with the national II stage, the particulate and NOx emissions were reduced by about 30%, respectively. With the implementation of the national III and national IV emission regulations in the country, it will reduce the emission of automobile exhaust pollutants and effectively reduce the harmful gas of air power, and play a great role in environmental protection.