Can anyone say about the idea of car fault diagnosis

1. Mechanical factors:

The efficiency of the car is reduced due to the breakdown, please return to the factory for maintenance to make sure that there is no fault.

Worn and worn car engines: overhaul of the engine.

2. Insufficient tire pressure: Please pay attention to the condition of the tire from time to time and maintain the tire pressure, which not only saves fuel but also prolongs the service life.

Brake bite: You can do a slow neutral coasting test by yourself to confirm that the brakes are not in this condition.

Hello First of all, do not blindly disassemble and replace parts, electronic faults should be detected by the computer first, and then the data flow should be checked, and then according to the fault ** to make a preliminary judgment of the damaged parts and accessories, and then repair (special conditions to view the circuit diagram). Mechanical faults should be checked for deformation or damage to the appearance first, and abnormal noise should be preliminarily judged by experienced technicians before careful inspection.

First of all, don't blindly disassemble and replace parts. For electronic faults, first use the computer to check the fault code, then check the data flow, and then make a preliminary judgment on the damaged parts and accessories according to the fault code, and then repair (in special cases, check the circuit diagram). Mechanical failure should first check whether the appearance is deformed or damaged, and after commissioning, the abnormal noise should be preliminarily judged by experienced technicians, and then carefully inspected.

Automobile fault diagnosis refers to the detection, analysis and judgment of determining the technical condition of the automobile or identifying the fault location and cause without disassembling (or only unloading individual small parts) when the car has hidden dangers, deteriorates its technical condition, or partially or completely loses its ability to work.

In automobile fault diagnosis, some diagnostic parameters are often used to characterize the technical dispersion state of automobiles, assemblies and mechanisms, such as the working process parameters of automobiles and the state parameters accompanying working processes. These parameters include physical quantities such as vibration, noise, temperature, vacuum, power, cylinder compression pressure, etc. ) and chemical quantities (e.g., exhaust gas composition, lubricating oil impurity composition, etc.)

Changes in these diagnostic parameters can correspond to changes in the technical condition of the vehicle and are highly reliable, sensitive, and achievable. In order to quantitatively evaluate these parameters, it is necessary to establish diagnostic parameter standards, such as national standards for vehicle driving safety and emissions, manufacturer's recommended standards related to technical conditions, and local and enterprise standards suitable for different regions and use conditions.

Millions of car purchase subsidies.

The symptoms of automobile failure, also known as the fault phenomenon, are the specific embodiment of the fault, and the car owner will classify and summarize it as necessary, which will help the diagnosis of the cause and location of the fault, and help the car owner to take corresponding measures according to the specific situation. So, what are the ways car owners can diagnose common car faults?

1.The sound is abnormal

Some faults can cause abnormal noise in the engine or chassis part of the car, which should be taken seriously, otherwise it is easy to cause mechanical accidents. Experience shows that where the sound is heavy and accompanied by obvious steep phenomena, it is mostly a malignant fault, and the machine should be stopped immediately to find out the cause.

General sounds often have different characteristics due to different causes, so you should listen carefully and distinguish them correctly when judging.

2.Abnormal consumption of fuel moisturizer

Generally caused by poor engine work or improper chassis adjustment, excessive consumption of oil, in addition to the cause of leakage, most of the engine is faulty, which is often accompanied by a large amount of smoke or pulsating smoke at the oil port, and the exhaust color is abnormal, the main reason is that the piston and the cylinder wall are too large or have serious wear.

3.Overheating

Overheating, usually manifested in assemblies such as engines, transmissions, transaxles and brakes. Under normal circumstances, these assemblies should be kept at a certain temperature, no matter how long the car has been working. Except for the engine, if you feel unbearable burning pain when touching it with your hands, it is an indication that the area is overheating.

Engine overheating indicates that the cooling system is a problem, if not eliminated in time, it will cause detonation, premature ignition, driving weakness, and even cause burn-out accidents.

4.Abrupt changes in operating conditions

The so-called sudden change in working conditions refers to the sudden abnormal phenomenon of the working condition of the car, which is a relatively common fault symptom, which is generally sudden, and should be dealt with calmly when encountering an accident. The common ones are: it is difficult to start after the engine suddenly stops, or even cannot start; The engine power suddenly decreases during driving, making driving weak; Sudden braking failure or deviation while driving, although the symptoms of this fault are obvious and easy to detect, but its causes are complex, and it is often from gradual change to sudden change, so at this time, you should be calm.

Pull over, if you have no experience, it is recommended to go to the maintenance office for repairs.

5.The color of the smoke exhaust is abnormal

For gasoline engines, the normal exhaust gas should be no obvious smoke, and when the oil is channeled on the cylinder, the exhaust gas is blue; When the combustion is incomplete, it is black; When the oil is mixed with water, it is white. The abnormal exhaust of the diesel engine is often a concomitant phenomenon that the engine is weak or not easy to start.

6.Leakage

Leakage usually includes oil, lubricating oil, cooling water, brake fluid and steering fluid, etc., which should not be taken lightly, and should be eliminated immediately once found, otherwise it will cause overheating, burning, etc.

1. Abnormal noise. During driving, we must pay attention to the sound of the engine under different working conditions, such as whether there is a knocking sound in the cylinder, whether there is a carburetor "tempering", whether the muffler has a "beat" or "burst", etc., once these abnormal noises are found, they must be solved in time. In addition, other parts are also prone to abnormal noise, so when you hear the abnormal noise of the car, you must pay attention to determine whether it is inside or outside the car, and then find out the location of the fault and solve it in time.

Two. Dashboard outliers.

Pay attention to the values indicated by each instrument to see if it is normal. If there is a red light, it should be noted that it generally means that a fault has occurred. In addition, it is necessary to pay attention to the color of the exhaust gas discharged from the muffler, whether the carburetor, gasoline pump and oil pipe joint are leaking, whether the engine is shaking, etc.

Once these problems are found, we should go to the repair shop in time to solve them.

Third, odors.

1.Burning smell.

If there is a burning smell, it may be caused by overheating and burning of the clutch plates. Clutch plates made of rubber, asbestos and other materials are mixed with a scorching odor. If it is not the clutch pads, check the brake pads and insist that the handbrake is fully released and the brake returns.

2.Battery odor.

If you smell a battery odor, it is usually caused by a leak in the electrolyte of a wet battery. When too much electrolyte is lost, the forced charging of the battery by the generator will overheat the battery, releasing white smoke and making the smell more pungent. As soon as an electrolyte leak is discovered, or the battery is obsolete, it needs to be replaced with a new one.

Some faults can be tested by various methods, such as honking the horn, turning on the ignition or light switch, and the spark plug "catching fire" and pulling the choke to quickly increase or decrease the engine speed. Sometimes, you can also replace a good component or part for a comparative test.

3.The taste of plastic paste.

Most of the smell of plastic paste is caused by overheating of the electrical circuit. The outer sheath of the wire is generally thin, and the smell of overheating is not great. When the wire is overheated and burned, there will be local smoke and the smell of plastic burning will increase.

Once you find that the wire is overheated, you should stop immediately to check and eliminate, and do not rush to continue driving, otherwise it will cause damage or even burn of the whole vehicle.

4.The taste of rubber paste.

The smell of rubber paste mainly comes from engine transmission belts, car tires and rubber hoses. If the engine belt is loose and slippery, the belt will rotate at high speed, and it will burn out due to poor heat dissipation. In this case, the machine should be turned off for inspection and replaced with a loose belt with a burning smell.

Constant over-braking while driving can put too much strain on the tires and create a rubbery smell. You need to pull over and drive after the temperature drops naturally. Cold water cannot be poured to cool the tires, which is not good for the health of the forum.

If the temperature is too high, some rubber hoses will emit a rubbery smell and should be checked for replacement.

Therefore, it is still necessary to find car problems as early as possible, pay more attention to details during normal driving, and do not relax those small car abnormalities, so that the problem can be detected and solved as soon as possible.

The automotive self-diagnosis system includes a special vehicle detector, a vehicle-mounted diagnostic system, and a multi-functional vehicle-mounted external diagnostic system.

Generally, cars equipped with microprocessor control units have fault self-diagnosis and sensitive systems. It can be used to automatically check and monitor the working status of each part of the transmission system and control system in the car.

When a sensor or circuit fails:

Its signal can no longer be used as the control parameter of the car, in order to maintain the operation of the car, the fault self-diagnosis module will call out the pre-set test value of the warp branch from its program memory, as the emergency input parameter of the circuit, to ensure that the car can continue to work.

The common methods of car fault diagnosis in daily life are intuitive diagnosis, observation auscultation, intuitive feeling, smell and smell and comparison, I recommend intuitive diagnosis, observation and auscultation, intuitive perception and smell. Because these four methods are relatively simple and easy to understand, and they are very convenient to operate, let's take a closer look at these methods.

1.Visual diagnosis.

Intuitive diagnosis method, also known as manual experience diagnosis method, refers to the diagnostic method in which the diagnostician, with rich practical experience and certain theoretical knowledge, relies on intuitive sensory impressions, with the help of simple tools, and uses means such as sight, ear hearing, hand touch and nose to carry out inspection, test and analysis, determine the technical condition of the car, and find out the cause of the fault and the fault location under the condition that the car does not disintegrate or partially disintegrate. The advantages of this diagnostic method are that it does not require special instruments and equipment, and can be applied anytime, anywhere, with low investment and quick results. The disadvantages are that the diagnosis speed is slow, the accuracy is poor, and the quantitative analysis cannot be carried out, and the diagnosticians are required to have a high level of technology and experience.

2.Observe auscultation.

Visually and directly observe the smoke color of the car and whether there are cracks, breaks, deformations, loosening, wear, air leakage, oil leakage, water leakage, etc., so as to determine the location of the fault. Listen to the sound inside the car by hearing and judge the fault of the car. A screwdriver is commonly used as a stethoscope or a special stethoscope is used to identify cylinder knocking, valve ringing, crankshaft bearing ringing, piston pin ringing, etc., so as to determine the location of the fault.

3.Intuitive Perception Method.

This method is based on the personal experience and feeling of the maintenance personnel when debugging the vehicle, and judge the fault of the car. If you touch the brake drum with your hand, you can judge whether there is lag in braking according to the temperature; Touch the high-pressure oil pipe with your hands, and judge whether the fuel injection pump is working normally according to the pulsation of the oil pipe. The intuitive perception method can also check for faults such as engine not easy to start, severe vehicle shaking, cab shaking, steering wheel and front wheel shaking, propeller shaft shaking, clutch slippage or incomplete disengagement, etc.

Maintenance personnel who adopt the intuitive perception method must have a certain level of diagnostic technology and rich practical experience.

4.Sniffing method.

Identify some special odors emitted by the car during use with the sense of smell, mainly including exhaust smoke smell, burning odor, etc., so as to determine the location of the fault. If the clutch friction pads and brake shoe friction pads are ablated, they will produce a foul odor, and the clutch slippage or brake lag will be judged accordingly. The smell of burnt rubber when the wiring harness is burned, and the smell of gasoline in the exhaust when the engine burns poorly, etc., can be used to determine the location of the fault.