Common faults of thermal power jet engine

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Common faults of EFI engine

when troubleshooting the faults of EFI engine, it is found that although the fault phenomena are different and the reasons are different, the typical faults are oxygen sensor, coolant temperature sensor and throttle position sensor. They not only have the characteristics of high failure rate, but also have a great impact on engine working conditions

1. Oxygen sensor failure

the abnormal operation of the oxygen sensor will affect the accurate control of the air-fuel ratio of the mixture by the computer ECU, resulting in the decline of engine power and economy and the deterioration of exhaust purification. At this time, the engine is prone to unstable idle speed, misfire, panting and chattering, and increased fuel consumption. Generally, when the oxygen sensor fails or the circuit is poorly connected, the ECU will store the memory and give a warning

the reasons for the early damage of the oxygen sensor are: the use of leaded gasoline makes lead stick to the working surface of the sensor and lead "poisoning" occurs; Silicon sealant is used in engine maintenance, and silicon dioxide generated after the combustion of silicon compounds contained in gasoline and lubricating oil leads to the failure of oxygen sensor; Sometimes the engine temperature is too high, which is also easy to cause early damage to the oxygen sensor

although the sensor has zirconia, titanium dioxide and other forms, its detection methods and data are also different. Now we introduce a generally applicable detection method: remove the wiring board of the sensor and make the probe of the voltmeter touch the connector at the sensor end. First, let the engine warm up at idle speed. At present, the company has signed a strategic cooperation agreement with some domestic new energy vehicle enterprises. Under this agreement, the data of the voltmeter should be greater than the reference value (the voltage on the oxygen sensor when the mixture is rich); Then turn the adjusting screw of the air flow meter to the left to dilute the concentration of the mixture (still maintain idle running), and then the voltmeter should be lower than the reference value (under the condition of thinner mixture, sometimes when the experimental force unloading of the oxygen sensor reaches the limit, it does not actively interrupt and continues to unload to generate voltage). The oxygen sensor is damaged and should usually be replaced. Some manufacturers stipulate that the oxygen sensor should be replaced after driving a certain mileage to keep the engine in good working condition forever

2. Coolant temperature sensor failure

this sensor provides important information for the computer ECU and is an important basis for the ECU to control the fuel injection quantity. If the sensor fails to work properly, it will cause the mixture control to be too rich or too thin, and most engines will have difficulties in cold starting, poor idle speed and increased fuel consumption. This sensor, ECU will store memory and warn

the detection method of the sensor is (take Toyota 2JZ-GE EFI engine as an example): Unplug the sensor harness plug and remove the sensor; Place the sensor in water and heat the water (the sensor terminal should be exposed to the water), and measure the resistance between the two terminals of the sensor at different temperatures at the same time; Compare the measured resistance value with the standard value (see table). If it does not meet the standard, it should be replaced

temperature (℃) resistance (K Ω)

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3 Throttle position sensor fault

the sensor transmits the throttle position signal to ECU, which uses this signal and other signals to determine the real-time working condition of the engine. If the sensor works improperly, it will affect the ignition advance angle and the air-fuel ratio of the mixture. At this time, the engine will show that there is no idle speed, and the speed is not easy to increase or even stall when accelerating

the disassembly and maintenance method of the sensor is: pull out the harness plug of the throttle position sensor; Check the continuity between the terminals with a multimeter. When the throttle is in the idle position, the middle and upper terminals should be connected; After the throttle is opened, the middle and upper terminals should be disconnected. If the result is inconsistent with the above, it should be adjusted

to ensure proper ignition advance angle and air-fuel ratio of mixture, the throttle position sensor must be adjusted correctly. The method is: start the engine, operate the throttle valve by hand to maintain the idle speed of the engine, loosen the two fixing screws on the sensor, rotate the throttle position sensor counterclockwise, and detect with a multimeter at the same time. First disconnect the middle and upper terminals, and then slowly rotate the sensor clockwise until the middle and upper terminals are connected: finally, fix the two screws on the sensor. If it fails to meet the requirements after adjustment, it shall be replaced

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