Causes of Common Faults in Vehicles and Their Diagnosis Methods

Because of the differences in design, materials, production processes, usage patterns, maintenance, and other differences, the automobile is inevitably subject to failure during use. Some car breakdowns are sudden and some are gradually formed. When a car malfunctions, it can accurately and quickly diagnose the cause of the fault with experience and scientific knowledge, identify the damaged parts and parts, and eliminate the fault as soon as possible, which is beneficial to the use and maintenance of the car. Therefore, analyzing the causes of failures, enumerating common major failures, and summarizing failure methods are conducive to making accurate judgments on vehicle failures.

First, the cause of automotive faults has its own vulnerable parts: In the design of automobiles, due to various factors, various functional requirements are different, and the parts have different life spans. For example, parts that work in harsh environments when moving on automobiles are vulnerable. Parts, such as engine bearings, spark plugs, etc.

The quality difference of the parts themselves: Automobiles and auto parts are produced in large quantities and produced by different manufacturers, and there are inevitable quality differences. There will be problems in the use of original parts, and problems will arise when the collaboration plant and unqualified parts are installed on the car.

The difference in the quality of automotive consumables: There are mainly fuel and lubricating oils. The poor quality of these products can cause carbon deposit in the combustion chamber and abnormal wear of the moving contact surface, which will seriously affect the performance of the car and cause failure.

Automotive use environment: The car is working in a changing environment such as open air in the wild. For example, if the road surface of the expressway is wide and flat, the speed of the car is high, and it is prone to malfunctions and accidents. The road is uneven, and the vibration of the car is severe and it is easily damaged. Power consumption in mountain areas is large, and it takes a long time to drive in cities. Inappropriate conditions can change the operating conditions of automobiles and cause malfunctions.

Impact of driving technology and routine maintenance: Driving technology has an impact on car failures. Inadequate routine maintenance of the vehicle's use management, failure to carry out regular and regular maintenance, and brutal start and savage driving will cause early car damage and failure.

The impact of automotive fault diagnosis technology and maintenance technology: If there is a fault in the car, it must be repaired immediately. If the fault occurs, an accurate diagnosis must be made before it can be repaired. In the use, maintenance, fault diagnosis and maintenance of automobiles, especially in modern automobiles, high-tech applications are more demanding. This requires that vehicle use and maintenance personnel must understand and master automotive technologies and advanced new technologies. It will not be repaired and cannot be repaired. It cannot be understood that it cannot be tampered with in order to prevent the old illness from being removed and new problems will emerge.

Therefore, automotive faults are widely present in the entire process of manufacturing, use, maintenance and repair of automobiles. Attention should be paid to every aspect. In particular, attention should be paid to the faults of the automobile in use. Faults must be discovered and eliminated in time. Only in this way can the car reduce accidents during its use.

Second, the main vehicle common failures Vehicle performance anomalies: The abnormal performance of the car is the vehicle's power and economic performance is poor, mainly in the car's maximum driving speed is significantly lower, the car's acceleration performance is poor; vehicle fuel consumption and oil consumption. The ride comfort of the car is poor, and the vibration and noise of the car are significantly increased. Poor vehicle handling and stability, the car is easy to run, the front side of the vibration; brake deviation, long braking distance or no brake.

Abnormal conditions in the use of automobiles: Some abnormal phenomena occur suddenly in the use of automobiles. Prevention should be emphasized: sudden engine flameout; no braking during braking; sudden steering failure during driving; even worse, car burst and auto ignition Wait. Symptoms are quite obvious, and the causes are more complicated. The main reason is that the internal car has not been noticed for failure and has developed into sudden damage.

Abnormal sound of cars: In the use of cars, it is often the most easy to express in the form of abnormal sounds, which can be heard by both drivers and passengers. Experienced persons can judge automobile faults based on the occurrence of abnormal sounds and the different frequencies and timbres of sounds. The general engine noise is relatively boring and the fault is more severe when accompanied by strong chatter. Stop, reduce the engine speed or turn off the engine to find Some voices can't be found out for the moment. Ask experienced personnel to find out. 1 e1 h-U8 K+v8～

Car odor: The most odor odor occurs when the car is driving, and the odor must firstly determine whether it is car odor. The car odor mainly includes the char odor from the friction material on the brake and the clutch, the special odor of the battery electrolyte, and the burning smell of the wire. At some point, you must be aware of the burning smell of oil leaked.

Car Overheating: Car overheating is manifested as the temperature of various parts of the car exceeds the normal operating temperature range. The performance of heat sinks is most obvious; transmission overheating, overheating of the axle housing, and overheating of the brakes can all be demonstrated by hand or water test. This is caused by high loads for a long time and rest. It is an internal organization failure that should be promptly diagnosed and eliminated.

Exhaust smoke abnormalities: Engine exhaust smoke is the appearance of the engine's work. The engine exhaust oil is blue, indicating that the engine is burning engine oil; the engine is not fully exhausted; the exhaust is black; the fuel should be replaced or the ignition timing adjusted; the engine exhaust is white, indicating that there is water in the fuel or in the cylinder, and the fuel should be checked. Or check the engine. ”

Car Leakage: Car leakage performance is fuel leakage, oil leakage, coolant leakage, brake fluid leakage, steering oil leakage, lubricant leakage and refrigerant leakage, and electrical system leakage battery fluid And electrical system leakage and so on. Vehicle leakage can easily cause overheating and damage to the vehicle. If the steering oil is drained, it can easily cause the steering of the vehicle to malfunction. Leakage of the brake fluid may cause the brake to malfunction.

The appearance of the car is abnormal: the appearance is abnormal. Care should be taken to check for abnormal conditions such as car tire pressure, frame and suspension damage, and body damage. May affect the safety of the car. Such as the car center of gravity shift, vibration, steering instability and car deviation and so on.

Abnormal driving of the vehicle: The abnormal behavior of the car driving is that the car can not accelerate according to the wishes of the driver, perform steering and braking, and can detect the malfunction of the vehicle operating mechanism and the actuator, except for the accelerator pedal, the brake pedal, the clutch pedal and the steering In addition to the inspection and adjustment of the disk and its transmission mechanism, a comprehensive inspection of the vehicle shall also be carried out. Identify the fault and repair it properly before using it.

Third, automotive fault diagnosis methods Automotive faults are ever-changing, all kinds of strange, a wide range, but the fault diagnosis methods and steps are certain, as long as the basic method is correct, clear ideas, methods properly, fault diagnosis is also easy to make. The method of fault diagnosis can basically be classified into 12 kinds: look-a-view method, observation method, auditory method, test method, touch method, olfactory method, replacement method, instrument method, metric method, sectional inspection method, partial disassembly method, etc. .

(I) Diagnosing faults with a look-and-see approach: Doctors need to “see and ask for cuts.” Car fault diagnosis is also the same. Among them, looking and asking are effective ways to quickly diagnose automobile faults. The breakdown of a car requires a diagnosis. When a repair person first sees a car, he or she should make a preliminary judgment of the form and age of the car. From the appearance, the form of the car can be understood. This is very important; When the engine is exposed in the room, the useful life can be judged. Experienced maintenance personnel can even make an automobile fault judgment. A car needs to be repaired. The maintenance personnel must ask the user and the owner of the car, including the model of the car, the service life, the repair situation, the use situation, the location and phenomenon of the malfunction, and what inspections and repairs have been done after the failure. It may be an in-depth understanding of faults. This is a shortcut. By understanding the form, you can reflect the basic structure and performance of the car. If you understand the form and structure of the car and have rich experience in maintenance, the diagnosis will be easier. If you do not know enough, you can grasp the book and the information. Through in-depth inquiry, you can basically understand where the fault occurred. For example, you can ask whether the fault occurred in the engine or the transmission; if it is the engine, you can further understand whether it is an electrical fault or a mechanical fault; if it is a mechanical fault, you can learn whether it is a crank connecting rod mechanism or a gas distribution mechanism, etc. Diagnosis is much easier. After the failure is determined, it is easy to eliminate and repair.

If the user talks about overhauling the car, he should also ask him to repair the engine powertrain, repair the automobile chassis, repair the automobile cab and body, repair the automotive electrical and automotive air conditioners, and so on. Which parts and assemblies are maintenance priorities, etc., in order to determine the maintenance program.

(B) the use of empirical methods to diagnose the fault: As the name suggests, empirical diagnosis of faults, is based on the basic qualities and rich experience of drivers and maintenance personnel, to quickly and accurately diagnose car faults.

The so-called basic quality, whether it is the driver or the car maintenance personnel, must be learned from the books and improved in practice so as to obtain basic automotive knowledge and maintenance experience. This is very important. Automotive technology is a comprehensive manifestation of the development of the national economy. The development of automobile technology is getting faster and faster, and new technologies are increasing. Therefore, it is not feasible to learn from the books without hard work. For example, the single-pump oil supply and speed control technology for diesel engines in automobiles and new technologies for new diesel engines in foreign countries all need to learn from books and learn from data on the basis of the original knowledge, and only then can maintenance work be carried out. Only practice under the guidance of theory is the correct practice, so that we can sum up and accumulate experience in practice. The so-called maintenance experience is also very important. With experience in vehicle maintenance, the same faults and similar faults can be solved at once. Experience has personal experience, summed up and accumulated experience; there are lessons learned from books and other ways. Only by combining the two can we continue to accumulate experience and make judgments on car faults more smoothly. For example, if the diesel engine malfunctions, the cab should be turned over. When the turning mechanism is stuck, the cab will not turn up. If the experienced person just pushes and pulls one, the cab will immediately reverse; for example, if a diesel coaster malfunctions, you will see it. The rapid increase in engine speed, louder and louder, no experience how to move can not make the diesel engine off, experienced as long as the fuel tank on the fuel transfer valve is turned 45, the diesel engine immediately turn off, to avoid a vicious accident. It is not difficult to see that this is the result of accumulated experience. Therefore, we must constantly sum up experience, turn experience into a powerful weapon for car maintenance, constantly arm ourselves with new knowledge and new experience, and use experience to solve all sorts of even complex and difficult problems on cars.

(3) Diagnosing faults by observation method: The so-called observation method is that a car mechanic carefully observes the fault phenomenon according to the location of the fault that the car user points out, and then judges the fault. This is one of the most basic and most effective applications. Fault diagnosis method. For example, the blue exhaust fumes on the exhaust pipe of the engine can be judged by the blue smoke phenomenon. For example, long-term emission of blue smoke during use, and the mileage of the engine is very long, the cylinder or piston ring can be generally judged as worn. , resulting in excessive clearance, due to the oil in the oil pan through the gap between the piston ring and the cylinder wall into the combustion chamber caused; if only when the engine is just starting to emit a blue smoke, then take the blue smoke again Gradually become relatively light, generally can be judged as the engine valve stem on the oil shield aging or wear hole to make the oil blocking function failure, and a small amount of oil leaked into the cylinder caused by the valve stem. Experienced persons can make accurate judgments, and those who lack experience should further observe. In the process of observation, we must also use our experience and theories to make thoughtful thoughts and inferences. We must not simply be hasty and we must not be confused by superficial phenomena. Some phenomena can not be seen clearly for those who have experience. Therefore, we must look at a few more times and observe carefully to be able to see through the symptoms.

(iv) Diagnosing faults by hearing: Diagnosing car and engine faults with hearing is a common and simple method. When the car is running, the engine operates with different operating conditions. The car and the engine as a whole emit a noisy but regular sound. When there is a fault in one part, an abnormal noise will appear, and an experienced person can immediately judge the automobile fault based on the abnormal noise. For example, the engine crankshaft and linkage mechanism ring, the main drive ring, drive shaft ring, can be easily judged. For a good driver, he should exercise listening in driving, hear the sound of various parts of the car, and judge abnormal noises and malfunctions. When a car and engine fail to be repaired, vehicle maintenance personnel often start the engine while it is stopped, allowing the engine to run at different speeds to auditively inspect and diagnose engine faults; for chassis and transmission faults, road tests are often used. The method allows the vehicle to travel in different conditions to inspect and auspicize the fault of the automobile. For the difficult problem of the engine, it can also be auscultated by means of a stethoscope and simple instruments. For example, a long rod auscultation rod can be used to auspicize crankshafts and linkages. The sound of the valve train can be heard; a hose can be inserted into the hole of the dipstick, and the crankshaft can be heard on the lower side of the oil pan and the sound of helium can be heard on the opposite side of the piston ring. When checking the brake in the parking state, the brake pedal can be stepped on when the engine is off and the brake can be clearly heard. When the brake pedal is raised, the brake shoe can be heard to return to its original position. Therefore, a well-trained driver uses a foot brake in driving. In addition to responding to the deceleration of the car, he can also hear the sound of the brake, so that it can comprehensively evaluate whether the brake is working properly. Therefore, as long as the car and the engine are running, there should be a loud sound. First, a good hearing should be heard. During the running of the car, the sound of the various parts of the car and the engine should be monitored. With the change of the speed of the vehicle, noises in different places are different, and the sound can be heard clearly. The sound, in the normal sound to determine the abnormal sound, in the abnormal sound to determine the fault, of course, there must be theory and experience to guide.

(V) Diagnosing faults with test methods: Diagnosing car and engine faults by using test methods is one of the commonly used methods. Test methods can be used to check the functions of automobiles and engines in the event that the car does not disintegrate or disintegrate, in order to achieve the purpose of diagnosing faults. The so-called test is to test to verify. If you don't know it, try it. For example, when a vehicle owner reports that the vehicle brake system is not working, the user can step on the brake pedal at the parking position of the vehicle. The brake system immediately sends out a set of braking actions. The tester can judge the failure of the brake system according to the sound of each brake. If it is still unclear for a moment, you can also try it on the road, step on the brake pedal under a certain speed, and the brake system works. The tester can respond to the brakes and the sound of each brake. Comprehensive judgment of the failure of the braking system. Similarly, for the failure of the steering system, the tester can turn the steering wheel in place, and a set of steering actions from the steering wheel to the wheel can determine the failure of the steering system. If the judgment is unclear, you can try the car on the open road, consciously turn the steering wheel on the curve, and work on the steering system. The tester can judge the failure of the steering system according to the reaction of the steering and the abnormal noise occurring somewhere. For the fault of the engine, it is necessary to check the operation of the engine. The tester runs the engine with different rotation speeds or acceleration and deceleration, observes the operation of the engine with experience, and auscultates the sound of the engine with experience, and generally can find faults. When one of the lights is off and the circuit is suspected to be without power, a wire can be used to short-circuit the ground to test the fire. When there is a fire, it can be judged that the circuit has electricity and no fire is checked. However, more fuses and relays are installed on the line, and the fire test must be performed with caution. The normal operation of the car and the engine has certain rules. If it is not normal, it means that a malfunction has occurred. The abnormality can be tested. For normal and abnormal judgments, there must be theory and experience as guidance.

(6) Diagnosing faults by touch: Human body and human hands and feet are sensitive sensory organs. It can be used to diagnose automobile and engine malfunctions, just like traditional Chinese medicine. Judging by the feeling of passing a car on the human body. When people ride in a car, the damage of the suspension system and the shock absorber can be judged based on the vibration of the vehicle in the vehicle. The driver is most sensitive and often drives a car, and the driver can feel it after the shock absorber fails. The car must be on the highway or at high speeds. Usually the driver must check the four wheels. Using the pedals to wheel tires can be used to determine the tire's air pressure. It is possible to determine the tightness of the wheel bearing based on the deflection and vibration of the tire. The solid condition is a typical foot touch method. After the car is driving on the expressway, the driver can touch the temperature of the tire with his hand. If the tyre is hot in summer, be careful. You can touch the brake drum by hand and try the temperature of the brake drum. Or, dripping with water on the brake drum, and looking at the evaporation of water, you can judge whether the brake drum is stuck. When it is found that the engine is overheated and there is coolant in the cooling system, the upper and lower parts of the radiator can be touched by hand. It can be judged whether the thermostat is damaged or the radiator inlet is blocked; touch the pump outlet hose to feel the pressure of the water flow Fluctuations indicate that the pump is working properly. Checking the tightness of the belt with the finger pressure, feeling the fuel pump with fingers, and checking the fuel supply of the high-pressure tubing by hand, are often encountered. In maintenance, the wear of the frictional surface is checked by hand, and the tightness of the friction pair is felt everywhere by hand. In short, the hand is an important organ of the human body, living is done by hand, there is a feeling in the work, and this feeling is the best device for fault diagnosis.

The odor of engine exhaust indicates that the engine burns oil and the engine is not completely burned. If the odor is greater, the engine should be adjusted or repaired when the car is more pronounced. The special odor of burning non-metallic materials means that the clutch friction plate is burned or the wire is burned. It is necessary to carefully check whether there is smoke at a certain place, or to ask if there is a fever somewhere to determine the location of the fault. The engine leaks engine oil and leaks into the running engine. The engine temperature is high and odor will occur. The engine oil will dribble on the exhaust pipe and a stronger odor will occur. The engine smell will easily enter the cabin from the air conditioner and can be clearly smelled. . Leakage of battery water (electrolyte) from the battery of an automobile can cause unpleasant odors; if the battery water is consumed excessively, the generator will forcibly charge the battery while the car is running, causing the battery to overheat, the battery to emit white smoke, and having a greater odor. Even people can be stunned and anyone can judge it. Leakage of other working media on the vehicle, such as power steering oil, transmission oil leakage, etc., can cause odors, but it must be carefully observed; leakage of vehicle-mounted articles or inflammable and explosive materials also requires attention. In short, once abnormal odor occurs during car operation, or when the odor is large, further inspections should be stopped to find out the root cause of the malfunction and take corresponding measures to eliminate odor. If car faults are to be solved, the car should be removed or repaired.

(h) Diagnosing faults by replacement: The so-called replacement method is an auto mechanic's replacement of potentially damaged assemblies and components with qualified assemblies and components, in accordance with what the car user may point out as a possible failure. This is a malfunction. A simplified and effective method of diagnosis. It is worth pointing out that replacement spare parts should be tested and reliable, or new parts must also be qualified products. If you accidentally replace bad parts with bad parts, not only can not find the fault, but will make the fault site False, increase the difficulty of diagnosis.

For example, if the oil pressure indicating system of the engine is faulty, when it is suspected that the pressure sensor plug is damaged, replace the pressure sensor plug on the original car with a good pressure sensor plug and try the car again. If the change is not good before the change, resolve immediately. The problem is that there is a failure in this part and it is immediately repaired. After repairing, you can remove the spare parts and replace them with a new one. If the replaced good items are still not good during the test, then the fault may not be here, then think of other ways to find. For difficult problems, there are many parts that can be replaced. For example, if the engine has insufficient power, a new air filter can be replaced and the vehicle can be re-tested. If the oil supply system fails, if a pump oil pressure is suspected to be insufficient, a new fuel pump or the like can be replaced. For the failure of the brake system, in the case that it is difficult to find out, you can try to replace a master cylinder (master pump). After the system is retuned, the brake system fault is eliminated. For the failure of the power steering system, if the steering is heavy, you can try to replace a power steering booster. After the system is recommissioned, the failure of the power steering system is eliminated. Then, through the above example, it can be shown that the fault occurred at the replacement. The replaced replacement assembly can also be replaced without removing it. This eliminates the need for maintenance procedures and serves two purposes. Some car mechanics have some commonly used spare parts such as headlights, small lamps, relays, fuses, etc. In the event that they encounter some failures and change their spirits, it is a simple, effective and reliable method of fault diagnosis. In order to apply the replacement method properly, the use of replacement method must be cautious, and the fault diagnosis should be consistent. Avoid blindly changing and increasing the workload.

(9) Diagnosing faults with instrumentation: Instrumentation is an indispensable tool for diagnosing automotive faults, and should be used whenever possible. Car instrumentation and indicators can effectively indicate the car's failure. For example, if the fuel gauge indicates the amount of fuel, when the vehicle does not move and the fuel gauge indicates zero, it indicates that the vehicle is not fueled, and not a malfunction has occurred. The brake warning light is on, indicating that the brake system is faulty and should be further searched. The voltmeter for automobiles indicates the voltage value of the vehicle's electrical system. It can also accurately determine the power generation of the generator and the charging of the battery during driving. Whenever an electrical device switch is used, the voltmeter is reflected, which can be used to judge. Is the electrical equipment working properly? Non-contact tachometers for automobiles can accurately measure the instantaneous engine speed, indicate the engine speed during driving, and indicate the change of engine speed when shifting. With the engine tachometer, some engine faults can also be caused by tachometers. Reflected. The cylinder pressure gauge for maintenance can measure the difference between the cylinder pressure and the pressure of each cylinder and the leakage condition of each cylinder; the multimeter can easily judge the fault of the automotive electrical system; the front wheel locator can also determine the front wheel alignment parameters. The sound level meter can measure the noise of automobiles and engines; the smoke meter, the fifth wheel instrument, the brake test bench, the car drum test bench, etc. are all the instruments and test equipments used in vehicle maintenance, if necessary. Use these special equipment. It is difficult to master the knowledge of instrumentation and electronic diagnostic equipment. It is necessary to have basic knowledge and to study hard in order to master and diagnose difficult problems in automobiles.

(X) Diagnosing faults by metrics: Applying weighers and instrumentation in accordance with national standards The metrics for various active parts and various parameters on automobiles are indispensable methods for fault diagnosis and debugging. Metric metrics are used for length measurements. Measurements related to length include micrometers, micrometers, plug gauges, feeler gauges, tape measures, etc. for measurements of diameter, clearance, and displacement; force and gravity measurements use force measurement. Gauges and gauges, etc.; pressures and vacuums are measured using pressure gauges and vacuum gauges. Various measurement instruments for automobiles also have a measurement unit, for example, a sound pressure level decibel value is used for the sound pressure measurement; a volt value is used for the voltage measurement. For the fault of the steering system, the front beam meter and the front wheel locator should be used to measure the front beam value of the steering wheel; the tire pressure should be measured with a tire pressure gauge; if necessary, the angle of the angular scale steering wheel can also be used to determine the accuracy of the steering system. Determine the cause of the fault. For the engine failure, the diameter of the cylinder barrel should be measured after the engine is disassembled, and the piston ring diameter, thickness and opening clearance should be measured to find out the exact cause of the failure in order to repair the engine; that is, to re-measure the cylinder barrel during the repair. Diameter, and according to the requirements of the grouping, matching pistons and piston rings can repair the engine. When diagnosing the failure of the electronic control system, it is inseparable from the measurement. For example, when the engine is unstable or the power is low, if the supply pressure is insufficient, the pressure of the system must be measured; if there is a problem with the electronic control system of the electronic control system, It is necessary to use a digital multimeter to measure voltage and resistance values; use frequency meters and oscilloscopes to measure frequency and waveform amplitudes. Therefore, various measuring instruments and scales are extensions of the maintenance staff's eyes and hands. Only correct measurement can accurately determine the situation. Based on the fact that the feeling is only superficial, the measurement method is combined with the instrument method. The more measuring instruments used, the more accurate the diagnosis should be.

(11)Diagnosing faults by means of sectional inspection: The so-called sectional inspection method means that the automobile mechanics check for faults according to the lines, pipelines and work paths with system properties on the car. The inspection can follow the system from the source of the power. The route search from the system to the executing agency can also be searched from the back to the front, or from the middle, depending on the examiner's experience. It is of course good to be able to find it from the executing agency, or you have to return to search from front to back. For example, for the failure of the lighting and indicating system, the principle should start from the front to the back of the power-switch-fuse-relay-wire-lightbulb circuit. Experienced persons can check the fuse first, and some people may check the light bulb firstly. People may check the relay first. When it is detected from front to back or from back to front, the problem may be in the middle. The combination switch may be broken, and there may be a broken wire somewhere. In the event of a failure of the brake system, the order of the brake pedal - vacuum booster - brake master cylinder - brake line - inductive proportional valve - brake line - wheel brake should be checked in principle. For those with experience, it is also possible to start the inspection from the wheel brake or the master cylinder and then check the other parts. However, for the difficult problems of the brake system, the measurement instrument should be used to check and measure from front to back. Can find the cause of the fault. In the event of a fault in the steering gear system, the order of the steering wheel-steer-steering gear-steering wheel should in principle be checked. For convenience, it can also be disassembled from somewhere in the steering gear, making it easier to determine if the fault is in the steering gear section or in the rear of the transmission mechanism. Using the existing theoretical knowledge, using a piecewise inspection method to conduct an orderly inspection can eventually find the source of the fault.

(12) Diagnosing faults by using partial disassembly: The so-called partial disassembly method is the time when an auto mechanic has found out that a fault has occurred on an assembly, and can't accurately determine which part of a specific fault occurred. The working principle of the assembly, partial removal of a certain part of the function to check, and then install the method. If the method is used properly, it can immediately determine the location of the fault. Therefore, the partial disassembly method is a simple and easy method for rapidly diagnosing automotive faults. There are many similarities between the partial dismantling method and the test method. The difference is that the partial dismantling method is mainly used for dismantling, and a method for diagnosing a fault after disassembling and retrying. For example, if a certain cylinder of the engine is suspected to be inoperative, a single-cylinder cut-off method can be used for inspection. Partial disassembly is the removal of the high-pressure tubing connection of the cylinder. The change in engine speed and sound indicates that the cylinder is working properly. And no reflection is that work is not normal. Insufficient Engine Power When air filter clogging is suspected, the air cleaner core can be removed and the engine can be retested. If the power is restored without the air filter, the fault is there. The partial dismantling method is actually to make the normal working engine or circuit system lose its original function, and to operate under abnormal working conditions, so the disassembly and assembly must be prudent. When it comes to safety projects, appropriate safety measures should be taken.

Applying these methods, we must have basic automotive structure and working principles as guidance; fully understand the use and maintenance of automobiles and fully understand the occurrence of failures. At the same time, some still need to rely on specialized fault diagnosis equipment to find, with instruments and equipment, but also will use, but also in combination with maintenance experience, flexible use of these fault diagnosis methods to make a comprehensive evaluation of the fault. Continuous practice in diagnosis, continuous summing up and accumulation of experience, will be applied freely. All fault diagnosis methods are complementary, the purpose is to find the car's failure. By using these fault diagnosis methods flexibly, you can find faults in cars, perform targeted repairs to cars and engines, and restore normal use functions.