What is the cause of the engine fault light on the dashboard?

Common faults of automobile engine and their elimination methods

When the automobile engine is not working normally, but the self-diagnosis system has no fault code output, it is especially necessary to rely on the inspection and judgment of the operator to determine the nature and location of the fault. The author summarizes the common faults of automobile engines as follows:

1. 1 Engine failed to start.

(1) Symptoms: Turn on the ignition switch and turn it to the start position, but the engine will not start.

(2) Possible causes of failure:

A. The engine can't rotate or rotates too slowly due to the failure of the starting system: ① the battery power is insufficient, the pole clamp is loose or the pole is seriously oxidized; ② The main fuse of the circuit is blown; (3) ignition switch failure; ④ Starter failure; ⑤ The starting line is open or the line connector is in poor contact.

B. Ignition system failure: ① The ignition coil is not working well, resulting in weak or no high-voltage spark; ② Igniter failure; ③ The ignition time is incorrect.

C. Fuel injection system failure: ① There is no fuel in the fuel tank; ② The fuel pump does not work or the pump oil pressure is too low; (3) The fuel pipe leaks and deforms; (4) the circuit breaker relay is disconnected; ⑤ The fuel pressure regulator is not working properly; ⑥ The fuel filter is too dirty.

D failure of air intake system: ① failure of idle speed control valve or its control circuit; ② The air pipe of idle speed control valve is broken or the connector leaks; ③ The air flowmeter is faulty.

E.ECU failure.

(3) Methods and steps of diagnosis and elimination.

① When the starting gear is set, neither the starter nor the engine can rotate, so it should be checked according to the fault of the starting system. Firstly, check the storage of the battery and the connection and contact of the pole; If the battery is normal, check the starting circuit, fuse and ignition switch; ② Step on the accelerator to the middle open position, and then start the starter. If the engine can still be started at this time, the fault is idle control valve and its circuit fault or air leakage in the intake pipe. If you step on the gas pedal to the middle open position, the engine still can't start, so check the next step. ③ Conduct visual inspection. Check whether the air inlet pipe leaks; Check whether the hose and its joint are in good condition; Check whether the crankcase ventilation hose leaks or breaks; ④ Check the high voltage spark. If the high-voltage spark is abnormal, check the high-voltage line, ignition coil, distributor and electronic igniter; ⑤ Check whether the ignition sequence is correct; ⑥ Check the oil supply of the oil supply system. Check the fuel supply pressure in the fuel pipe when it is confirmed that the fuel tank is torn; ⑦ Check the ignition timing and ignition sequence of each cylinder; ⑧ Check the working condition of the fuel pump switch installed on the air flowmeter; Pet-name ruby check the working condition of each cylinder spark plug; Attending to check the ignition timing. If the ignition timing is incorrect, further check the ignition timing control system; ? B 1 1？ Check the power supply and working condition of ECU to determine whether it is a fault of ECU.

1.2 engine stall fault

(1) fault phenomenon: when the engine is working, the speed rises and falls, which is called engine stall phenomenon, and its fault is called engine stall fault.

(2) Cause of failure: The reasons for the high and low engine speed include fuel nozzle system failure, ignition control system failure and air intake system failure. Common reasons for failure are as follows:

① Air leakage in the air intake system. For example, leakage of hoses and connectors, leakage of PVC valves, leakage of EGR system, leakage of dipstick socket and leakage of oil filter cover. ② The air filter element is too dirty; ③ The air flow meter is not working properly; ④ The supply pressure of the fuel injection system is unstable. Such as tubing deformation, poor connection and contact of system lines, insufficient pump pressure of fuel pump, unstable operation of fuel pressure regulator, dirty fuel filter, jitter of relay contact of circuit breaker, etc. ⑤ The ignition timing is incorrect; ⑥ The cold start injector and temperature timing switch are not working properly; ⑦ECU failure.

(3) Diagnosis and elimination methods and steps: ① Check whether the air inlet pipe leaks. Check all hoses and connectors, PVC valve pipes, EGR system, dipstick socket and oil filter cover; ② Check the oil supply pressure. Check whether there is too little fuel in the fuel tank and the pressure in the fuel pipe is unstable. The specific method is the same as when checking that the engine cannot be started; ③ Check whether the air filter element is too dirty; ④ Check the ignition advance angle; ⑤ Check the working conditions of spark plugs in each cylinder; ⑥ Check the working conditions of cold start injector and temperature time control switch; ⑦ Check the output voltage of air flow meter and its relationship with engine working conditions; ⑧ Check the fuel injection quantity of the fuel injector; Pet-name ruby check the working condition of ECU.

1.3 engine idling fault

(1) symptom: the engine works normally when it runs above the medium speed. When the vehicle speed is at or near the idle speed, the phenomenon of unstable idle speed or even flameout occurs, which is called poor idle speed fault.

(2) Cause of failure: Poor idle speed is usually caused by intake system and fuel injection control system, and occasionally caused by engine mechanical failure. The common causes of poor idle speed are: ① air leakage in the intake system; ② The cold start injector and temperature time control switch are not working properly; ③ Abnormal oil supply pressure of fuel injection system; (4) Nozzle failure leads to poor atomization quality; ⑤ECU failure.

(3) Diagnosis and elimination methods and steps: ① Check whether the air inlet pipe, PVC valve hose and dipstick are leaking; ② Check whether the air filter element is too dirty; ③ Check whether the cold start fuel injector and temperature time control switch are normal; ④ Check whether the fuel system pressure is too low; ⑤ Check the injection of the fuel injector; ⑥ Check cylinder pressure and valve clearance when necessary; ⑦ Check ECU.

1.4 mixture is too lean.

(1) fault phenomenon: the engine speed is unstable, the power is obviously insufficient, and there is backfire. It can be considered that the engine has a fault of too lean mixture.

(2) Cause of failure: ① Air leakage in the air intake system; (2) cold start injector and temperature timing switch failure; ③ The system fuel pressure is too low; ④ The fuel injector is stuck or blocked; (5) air flowmeter failure; ⑥ Water temperature sensor failure; ⑦ Fault of throttle position sensor; ⑧ECU failure.

(3) Diagnosis and elimination methods and steps: ① Check whether the air intake system leaks; ② Check the timing switch of cold start injector; (3) Check whether the fuel injector is blocked; ④ Check the working condition of the air flow meter; ⑤ Check the water temperature sensor; ⑥ Check the operation of the throttle position sensor; ⑦ Check the input and output signals of each terminal of ECU.

1.5 Accelerated failure

(1) Fault phenomenon: When the throttle is slowly accelerated from low speed to high speed, the engine works completely normally, but when it is rapidly accelerated, the engine speed changes slowly, and sometimes there is panting or backfire.

(2) Cause of failure: ① Air leakage in the air intake system; ② The system oil supply pressure is too low; ③ The ignition voltage is too low; ④ The ignition time is too late; ⑤ Cylinder pressure is too low or valve clearance is too small; ⑥ The throttle position sensor is not working properly; ⑦ECU failure.

(3) Diagnosis and elimination methods and steps: ① Check whether the air intake system leaks; (2) check the high voltage spark; ③ Check whether the ignition advance angle is normal; ④ Check the system oil supply pressure; ⑤ Check whether the throttle sensor works normally; ⑥ Check whether the signals of each terminal of ECU are normal; ⑦ Check the valve clearance and cylinder working pressure when necessary.

2 engine fault diagnosis and elimination flow chart

2. 1 Flow chart of engine fault diagnosis and elimination

The main reason why the electronically controlled engine cannot rotate or rotates slowly is that the battery or starting system is faulty. Check the battery and the starting system for troubleshooting: If the crankshaft rotates normally, the engine can't start, mainly because the sensors, actuators, electronic control units and their circuits of the fuel injection system are faulty, which can be eliminated according to the procedure shown in Figure 1:

2.2 Flow chart of fault diagnosis and elimination of poor acceleration or flameout

2.3 engine idle speed is poor or flameout.

The main cause of poor idle speed or flameout is the failure of idle speed control system, which can be eliminated according to the procedure shown in Figure 3:

3 Matters needing attention in detection and maintenance

3. 1 Maintenance Points of Electronic Control Engine

(1) Controlling the gasoline injection system requires high cleanliness of gasoline, and leaded gasoline with brand and quality completely meeting the requirements should be used. The fuel filter should be replaced regularly to prevent foreign matter in the fuel from blocking the injector.

(2) Use the power supply in strict accordance with the requirements. The polarity must be correct when installing the battery, otherwise the electronic components will burn out.

(3) Try to avoid violent vibration of the computer and prevent moisture from soaking into all parts of the electronic control system.

(4) When the engine cannot be started normally due to insufficient battery power, the battery should be charged or replaced with a new battery in time, and try not to start the engine by jumper circuit.

(5) Don't flush the microcomputer control unit and other electronic equipment with water. The ambient humidity for storing the engine should not be too high. Try not to wash the floor with water in summer.

(6) Protect the microcomputer system from severe mechanical shock and vibration.

(7) The engine should be far away from the electrical equipment that can emit electromagnetic fields, so as to avoid the interference of strong electromagnetic fields in space on the microcomputer system.

3.2 Inspection Points of Electronically Controlled Fuel System

(1) When the ignition switch is turned on and the engine is not started, the warning light should light up. After the engine starts normally, the warning light should go out. If it doesn't go out, it means that the computer self-diagnosis system has detected a fault or an abnormal phenomenon. At this time, the battery cannot be disconnected from the circuit to prevent the loss of fault codes and related information stored in the microcomputer. The fault of electronic gasoline injection system should be judged according to the flashing times of warning lamp or the output fault code, which should be read by special equipment.

(2) Before the oil supply system is overhauled, the grounding wire of the battery should be removed first.

(3) The electric gasoline pump is not only controlled by the ignition switch, but also controlled by the switch in the air flowmeter. After the ignition switch is turned on, the gasoline pump will continue to work only when the engine is working normally or starting, the air flow meter detects the air flow signal or the microcomputer detects the speed and ignition signal. Its oil outlet pressure is higher than that of general oil supply system. After being damaged, it can only be replaced by the original electric gasoline pump.

(4) When overhauling, no matter whether the engine is running or not, just turn on the ignition switch and never disconnect any working electrical equipment. Because these devices often have certain inductance, when their working current is suddenly cut off, high instantaneous voltage will be generated in the circuit, which will cause serious damage to electronic devices.

(5) If arc welding is needed, disconnect the power cord of the electronic control unit.

(6) When overhauling the microcomputer and the sensors and actuators connected with it, the operator must eliminate the static electricity in advance, and must bring an iron-connected metal belt, one end of which is wrapped around the wrist and the other end is clamped on the car body, so as to avoid electrostatic damage to the microcomputer system.