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For electronic control system fault diagnosis of electronically controlled engines
1. Ask the user, the time, phenomenon, situation at the time of the failure, the reason for the failure and whether it has been repaired or disassembled.
2. Preliminarily determine the scope and part of the fault.
3. Call up the fault code and check the content of the fault.
4. According to the fault range displayed by the fault code, carry out maintenance, especially pay attention to whether the joint is loose and falling off, and whether the wire connection is correct.
5. After the maintenance is completed, it should be verified whether the fault has indeed been eliminated.
6. If the fault code cannot be adjusted, or the fault content cannot be found after the call, the fault range is roughly judged according to the fault phenomenon, and the working performance of the components is checked one by one to be eliminated.
Common troubleshooting
The engine does not start or has difficulty starting
1
The starter does not turn or rotates slowly
1) Check the battery voltage.
2) Check whether the battery pole, wire connection, etc. are loose.
3) Check the starting system, including ignition switch, start switch, neutral start switch and starter, and whether the connection of each line is loose.
2
The starter rotates normally, but the engine cannot be started
1) Call up the fault code.
2) Check the working condition of the fuel pump.
3) Check whether the idle system is working properly (if the idle system is not working properly, the engine can start when you step down the accelerator pedal).
4) Check the ignition system, including high-pressure sparks, ignition timing, spark plugs, etc.
5) Check whether there is any air leakage in the intake system.
6) Check whether the air flow meter or air pressure sensor is not working properly.
7) Check whether the injector and low temperature start injector are working properly.
8) Check the EFI system circuit, including the ECU connector related terminals.
9) Check the mechanical part for failure.
Poor engine idle
1) Call up the fault code and analyze the cause of the fault.
2) Check the air intake system for air leakage.
3) Check the working condition of the PCV valve of the crankcase ventilation duct (the PCV valve should be closed when idling).
4) Check whether the idle adjustment screw on the throttle is correctly adjusted, if the adjustment screw adjustment is incorrect, it will cause the mixture to be too thin when idling, resulting in unstable engine idle.
5) Check the timing of the ignition.
6) Check the injection of the injector.
7) Check the working condition of EFI system circuits and components.
8) Check the condition of the mechanical system.
Idle is too high
1) Check whether the throttle valve is issued and cannot be closed.
2) Check if the cold start injector continues to inject fuel.
3) Check if the throttle position sensor has an incorrect output voltage.
4) Check whether the fuel injection pressure is too high.
5) Check the pressure regulator vacuum sensor hose for shedding or breaking.
1) Check whether the idle speed control system and VSV valve are working properly.
2) Check the injector injection situation and whether it is dripping.
3) Call up the fault code to determine the cause of the fault.
4) The operation of the EFI system circuits and components.
10) Check whether the ignition timing is incorrect.
Engine speed is unstable
3) Check the fuel pump oil supply situation, whether the pressure of the fuel line is normal.
4) Check if the fuel pressure regulator is not working properly.
5) Check the injection situation of the injector, whether the individual injectors are not working or the amount of fuel injected is not accurate.
6) Check the ignition system, such as ignition timing, high-pressure spark situation, spark plug carbon deposit, etc.
7) Check if the air filter element is blocked.
8) Check if the gasoline filter element is blocked.
9) The operation of the EFI system circuit and components.
10) Check the mechanical parts, such as cylinder pressure, valve clearance, etc.
Engine tempering
Most of the engine tempering phenomenon is caused by the dilution of the mixture or the late ignition time.
1) Call up the fault code and analyze the cause of the fault.
2) Check the intake pipe for air leakage.
3) Check whether the output signal of the throttle position sensor is correct.
4) Check the timing of the ignition.
5) Check if the fuel pressure is too low.
6) Check whether the injector injection time is too short.
7) Check whether the injector is blocked by the hairpin.
8) Check the working conditions of EFI system circuits and components, mainly relevant sensors, such as oxygen sensors, water temperature sensors, intake air temperature sensors, intake pipe pressure sensors, etc.
Exhaust pipe firing cannon
The phenomenon of exhaust pipe firing is mainly caused by incomplete combustion factors such as excessive concentration of mixed gas, non-working of individual cylinders and incorrect combustion time.
2) Check whether the ignition time is too late.
3) Check if the cold-start injector is still injecting oil or dripping, and further find out the cause.
4) The low temperature start injector timer switch fails.
5) Individual cylinder spark plugs are not ignited or the sparks are too weak.
6) Check the injector for excessive injection, or excessive injection of oil in individual cylinders, and whether there is dripping.
7) Check whether the fuel pressure is too high, whether the pressure regulator fails so that the return oil line cannot be opened to return oil, and whether the pressure regulator vacuum sensor hose falls off or breaks.
8) Check whether the output signal of the air flow meter sensor and the throttle position sensor is correct.
9) Check the operation of the EFI circuit and related sensors.
Poor engine acceleration
1) Check the intake pipe for air leakage.
2) Check if the ignition time is too late.
3) Call up the fault code and analyze the cause of the fault.
1) Check the fuel injection system, such as fuel pressure, injector working condition.
2) Check whether the ignition system, especially the detonation sensor and igniter, is working properly.
3) Check whether the throttle position sensor is normal.
4) Check the operation of EFI circuits and components related to fuel injection.
5) Check the cylinder pressure, valve clearance, spark plug working conditions and gas distribution phase and other items.
Typical component failures and their causes
ECU
In general, the ECU is more reliable, not easy to fail, under normal use, the failure rate of 100,000 kilometers is not higher than one thousandth, but when the engine working time is too long (driving mileage of more than 150,000 kilometers), the failure rate of the ECU is significantly increased, the cause of the failure is mainly:
1) Loosening of solder joints;
2) Capacitor element failure;
3) The integrated block is damaged;
4) The electronic control unit fixing foot bolt is loose;
5) Damage to electronic components.
Once the ECU fails, it will cause the engine to fail to start or difficult to start, no high speed, large fuel consumption and other phenomena.
sensor
Vehicle sensors are generally divided into thermistor type, vacuum pressure type, mechanical transmission type and piezoelectric type, relatively speaking, the sensor in the electronic control gasoline injection system is prone to failure, the cause of failure is mainly:
1) Elastic component failure;
2) The vacuum diaphragm is damaged;
3) Wear or ablation of the contact part;
4) Peripheral line failure, etc.
The sensor is responsible for providing the engine operating conditions to the ECU, so in general, when there is a failure, it will directly affect the source of accurate information about the ECU, and the control of the engine will also be out of control or abnormal.
Plug in and out connectors
Electronically controlled gasoline injection systems have a large number of connectors, because they work in a vibrational, dusty, high temperature, moisture-prone environment, over time, it is easy to cause failure. The main causes of failure are caused by a harsh environment:
1) Connector aging failure;
2) Loosen the joint;
3) The connector is in poor contact.
When the connector fails, the engine work is unstable, good and bad, and it can generally be diagnosed by the fault indication simulation test method.
Injectors and cold start injectors
Injectors and cold-start injectors are one of the wearing parts, especially due to the relatively poor oil quality of domestic gasoline, which is more prone to blockage and jamming. Under normal circumstances, the injector should be cleaned at least once a year. The failure of the injector is mainly manifested in:
1) The electromagnetic coil is not working well;
2) The injector nozzle is stuck;
3) Blockage;
4) Drip;
5) The atomization condition is not good;
6) Peripheral circuits.
Injector failure mainly causes a certain cylinder of the engine not to work or work poorly. In addition, the amount of fuel injected by each cylinder injector is too large (more than 8 to 10ml in 15 seconds), which will also cause failures such as unstable work of the entire engine.
Vacuum hoses and other pipes
The electronically controlled gasoline injection system has a large number of vacuum tubes and other pipes, because most of them are rubber products, heated, oiled and over time, it will produce aging. Its failure is mainly manifested in:
1) Hose aging;
2) Rupture of the nozzle;
3) The card is not clamped;
4) The interface is loose.
It is eventually manifested as air leakage, which makes the mixture too thin, the engine has difficulty starting or idle, and the acceleration is weak.
Fuel pressure regulator
The fuel pressure regulator is used to adjust the injection pressure, and when there is a failure, it will obviously affect the fuel supply of the engine, making the engine oil supply unstable, difficult to start, and weak acceleration. Clogged channels and damage to the diaphragm inside the pressure regulator can cause the fuel pressure regulator to fail.
Filter
Clogging of air filters, gasoline filters and oil filters can cause engine failures, so they should be maintained regularly and replaced if necessary.