The acceleration of the car is weak, and the inspection of the maintenance shop is the engine fire,

If your car has a fault such as shaking and weak acceleration, you will often check the fault code of "engine fire" when you go to the repair shop for inspection. Many people think that "engine misfire" is "spark plug did not ignite", but the spark plug, ignition coil, etc. were replaced, and the fault was still not eliminated, but the final failure point was in the mechanical aspect. Today we will talk about what exactly is an engine misfire and what causes it to cause an engine misfire.

The so-called engine misfire refers to the fact that one or several cylinders of the engine do not do work or do insufficient work, which is what we usually call "engine cylinder shortage". After the engine misfires, there will be serious shaking, the engine power is insufficient, the car is unable to accelerate, and the fuel consumption is high. If a multi-cylinder misfires, the engine may not start.

The engine misfire is judged by the crankshaft position sensor by monitoring the speed fluctuation when the crankshaft rotates, and the ignition work of the normal four-cylinder engine will have 4 small fluctuations in the speed of the crankshaft; If this fluctuation is reduced, it means that there is a cylinder that is not doing work or is doing poor work; Then, with the help of the camshaft position signal, it can be identified which cylinder is misfired; When the misfire rate exceeds the limit value, the engine control unit records the fault code and lights up the fault light.

There are many causes of engine fires, which can be roughly summarized into two major aspects: electronic control system failure and mechanical part failure. Electronic control system faults, such as sensor signal missing or signal inaccuracy, control unit failure, wrong control signal or no signal output, spark plug or ignition coil damage resulting in failure to ignite, injector non-fuel injection, and line connection failure; The failure of the mechanical part is mainly due to the insufficient pressure of the cylinder, such as the valve is not closed tightly, air leakage, etc., and the gap between the cylinder, piston and piston ring is too large, resulting in insufficient compression.

In terms of specific operation, we first have to check the fault of the electronic control system to see if the spark plug is ignited, and then follow the line to find the fault point until we find the fault point. Generally spark plug and ignition coil faults, some four-cylinder engines use two cylinders to use an ignition coil arrangement, generally 1-4 cylinders share one, 2-3 cylinders share one, if one ignition coil is damaged, it may lead to two cylinders at the same time.

If the spark plug ignites properly and the injector injects normally, it is time to check the mechanical aspects. Generally, the cylinder pressure of the engine is measured first, and if the pressure of a cylinder is significantly low, it means that the cylinder is not working. In order to further determine whether the valve seal is not tight or the piston ring seal is not tight, we can inject some oil into the cylinder, and then measure the cylinder pressure, if the cylinder pressure rises, it means that the piston ring seal is not tight; If the cylinder pressure is still low, it means that the valve is not tightly sealed.

Generally, this situation requires the engine to be disassembled.

Upstairs is the truth! In the end, it was due to a valve leak!

Spontaneous combustion caused by line failure, which is mainly due to the problem of line aging, overload, short circuit, poor contact or wear and tear, can generate very large heat. If the quality of the wire is not good enough, or there are many flammable and explosive items around, it is easy to cause spontaneous combustion accidents. For example:

The skin between the cable and the frame and the clamp is broken due to vibration friction; Tail lights, brake lights, wires, etc. are broken due to vibration and friction; The installation of the lamp holder is loose and damaged due to vibration and damage to the connectors, which will cause the vehicle to "catch the iron" and jump over for a long time when the vehicle is driving or parking, resulting in high temperature, causing insulation damage of electrical appliances, switches and wires, and then increasing the scope of the flashover, expanding the high temperature area, and finally leading to spontaneous combustion and fire in contact with paint, leaked gasoline, flammable materials, etc.;

The most common electrical short circuit of wire short circuit is that the starter switch is welded due to contact sintering, and the starter magnetic switch cannot be released, resulting in the starter starting for a long time (the safe starting time of the starter is 5s), resulting in the starter heating **. In addition, in some single-wire cars, the insulator of the live wire is damaged and the "tie iron" or the electrical "tie iron" will cause short circuits, especially for some vehicles that have been used for a long time, the lines are dilapidated and the lines are arranged in a chaotic manner. The "protector" of the wires on the car is the fuse, and once the wire is short-circuited and a large current is generated instantaneously, the fuse will be quickly blown out.

However, if the fuse is too large, for example, someone tries to replace the standard fuse with copper wire, resulting in the loss of protection function, it may cause a short circuit in the wire and cause a fire;

Because the cars produced now are generally equipped with three-way catalytic reactors, and the temperature of this device located on the exhaust pipe is very high, generally 300 to 400, so once there are flammable materials at the bottom of the car at this time, it will be easy to be ignited by the three-way catalytic device, resulting in spontaneous combustion of the vehicle.

The cause of a fire in a car engine.

1. Fuel system leakage.

The most common cause of vehicle fires is a leak in the fuel system. All kinds of fluids in the car have flammability, toxicity, corrosiveness and other characteristics, among which fuel contains these three types of characteristics. Gasoline only needs to be exceeded, and it can ignite quickly, and this type of combustion occurs all the time in a moving car – inside the engine, of course.

In addition, gasoline spontaneously combustifies when reached. The only thing you can do to prevent fuel system triggers** is good maintenance. When you smell gasoline near your car, immediately check the fuel system for leaks.

2. Electronic system failure.

The reason why electronic system failure is listed as the second cause of vehicle failure is that among many accidents, electronic system failure does occupy a certain proportion. If a car battery fails, the charging process can cause hydrogen to occur in the engine compartment**. In addition, if the wiring harness connected to the battery is loose, the leaking current will react with the droplets and the leaked vapor during the battery transmission current, resulting in **.

The hazards of electronic system failure are not limited to one locality, but can be found throughout the car, including inside the doors, under carpets, and under the seats.

3. All kinds of oil spillage.

Under the hood of every car, there are all kinds of fluids——— fuel, engine oil, transmission oil, steering oil, brake fluid, coolant, and so on. When the car is in motion, all of these fluids are in the working cycle, and any problems with the tightness of the conduit in the circulating system that contain these fluids can cause a fire if the fluid leaks. Some of these fluids are circulated only in the engine compartment, while others flow through the entire vehicle, such as brake fluid.

4. The engine is overheating.

An indirect vehicle caused by an overheated engine is a good example of a ripple effect. It is impossible for the car engine itself to overheat to a temperature high enough. However, it is able to keep the coolant, oil and other liquids in the engine compartment above the standard operating temperature.

If this happens, the liquid will spill out and spray all over the engine compartment, with a high chance of coming into contact with other hot components**.

There are many reasons for the wheel of the engine, which can be roughly summarized into two aspects: electronic control system failure and mechanical part failure. Electronic control system failures such as missing or inaccurate sensor signals, faulty control unit control signals or no signal output, damage to spark plugs or ignition coils leading to ignition failures, injector failures, and line connection failures.

Mechanical failures are mainly due to insufficient cylinder pressure.

Engine misfire refers to the phenomenon that the mixture in the cylinder is not fully burned or cannot be burned due to the ignition system, oil supply system, abnormal cylinder pressure or other reasons. Depending on the degree of combustion anomaly, fires are divided into partial fires and complete fires. Partial misfire refers to incomplete combustion of the mixture in the cylinder; A complete lack of fire means that the mixture does not burn in the cylinder to do work.

According to the frequency of misfires in the working cycle, misfires can be divided into continuous misfires and single misfires. Continuous lack of fire refers to the phenomenon of continuous lack of fire in the cylinder during the operation of the engine. A single misfire refers to the phenomenon that the misfire cylinder sometimes works normally and sometimes misfires during the operation of the engine.

After the occurrence of engine misfire failure, it will lead to unstable engine operation, reduced power performance, and poor fuel economy. At the same time, the incomplete combustion mixture will continue to burn in the exhaust system, which will increase the burden on the three-way catalytic converter, and even cause it to be damaged due to high temperature. Therefore, the exhaust gas is also in a substandard state, which will aggravate the pollution to the environment.

If such a malfunction occurs, it should be repaired in time.

Automobile engine fire is mainly manifested in the single cylinder (or multi-cylinder) does not work or works poorly, resulting in the main reasons for cylinder fire is the following five points: 1. Ignition system failure: such as ignition timing disorder, spark plug gap is abnormal, carbon deposit, breakdown of high-voltage line leakage, ignition coil breakage, short-circuit ignition module and line failure, etc.

2. Failure of fuel supply system: such as low fuel pressure, too high fuel injector coil break, short circuit, mechanical stagnation, etc. 3. Air intake system failure:

Such as clogged air filter, air intake system leakage, etc. 4. Insufficient cylinder pressure: such as failure of the valve mechanism, poor sealing between the piston ring and the cylinder wall, damage to the cylinder gasket, etc.

5. Other faults: other faults of the engine electronic control system.

The causes of engine misfire are as follows: 1. Ignition system failure. 2. Failure of oil supply system.

3. Air intake system failure:4. The cylinder pressure is not enough for socks. 5. Engine electronic control system failure.

The hazards of engine fire are as follows: 1. Cause the engine to work unsteadily, the power performance decreases, and the fuel economy deteriorates. 2. Increase the burden of the three-way catalytic converter, and the exhaust gas discharged is not up to standard, causing pollution to the environment.

The following is an introduction to the engine: the engine is a kind of machine that can convert other forms of energy into mechanical energy, which is not only suitable for the power generation device of the cong hall, but also refers to the whole machine including the power unit (such as gasoline engine, aero engine), the type of engine includes internal combustion engine, external combustion engine, electric motor, etc.