When the BMW 520 brakes, the engine tachometer will shake up and down

1) Check whether the engine is obviously overheating, and if so, find out the cause first. (There are many related causes of engine overheating, pay attention to analysis).

2) Check if the engine knocks due to the failure of the ignition system.

If the ignition advance angle is too large, the mixture will burn too fast, resulting in engine knock combustion. The reasons for the excessive ignition advance angle are as follows: the crankshaft position sensor is installed in the wrong position (or loose), the timing belt is installed in the wrong tooth, the operation program of the power control module is faulty, the air intake detected by the air flow sensor is too small, and the detonation sensor is slow to respond.

3) Check if the pressure in the fuel system is too low.

If the pressure of the fuel system is too low, causing the mixture to be too thin, the combustion rate of the mixture will decrease, and the heat transferred through the cylinder wall to the coolant after the mixture is burned will increase, resulting in a high engine temperature. The engine temperature is too high, which is prone to detonation and combustion.

4) Check if the fuel is contaminated.

The lower the designation (i.e., octane number) of gasoline, the less resistant the gasoline is to knock off, and the more susceptible the engine is to detonation combustion when using this gasoline as fuel. In addition, if impurities are added to the gasoline with a relatively high grade, it will also cause the anti-knock ability of the gasoline to decrease.

5) Check whether the engine knocks due to the failure of the engine cooling system.

The actual working temperature of the engine is determined by the heat generated by the combustion of the mixture per unit time and the heat emitted by the heat dissipation system, if the cooling system is faulty, the former will be greater than the latter, the temperature of the engine will be higher and higher, and the tendency to detonation and combustion will be greater and greater.

6) Check if the pressure of the cylinder is too much.

If the pressure of the cylinder is too high, the combustion rate of the mixture increases, and the likelihood of detonation combustion in the engine increases. The reason for the excessive pressure of the cylinder is that the cylinder head, piston or cylinder gasket model is not the same as the working volume of the cylinder and the cylinder pressure.

7) Check whether there is too much carbon deposits in the combustion chamber of the engine.

If a large amount of carbon deposits accumulate in the cylinder, the hot spots formed by the carbon deposits may ignite the mixture in advance during the cylinder compression process, causing the pressure in the cylinder to suddenly increase during further compression, resulting in detonation and combustion. The causes of carbon deposition are as follows: the mixture is too concentrated, the ignition energy is relatively poor, the quality of gasoline is relatively poor, and the engine burns oil for some reason, etc., which can be checked separately.

8) Check if the EGR system is working properly.

If the exhaust gas recirculation system works within the working range, the system fails and cannot make the exhaust gas enter the cylinder to participate in the combustion, which will inevitably cause the combustion temperature of the mixture to rise, so that the engine will overheat and be prone to detonation combustion.

9) Check if the application and calorific value range of the spark plug are correct.

Hello, it is recommended to check the check valve on the vacuum line.

What is engine super knocking.

Engine "super knocking", also known as low-speed premature ignition, is an abnormal combustion phenomenon unique to supercharged direct-injection gasoline engines. When the engine inhales the mixture of fuel vapor and air, in the process of compression, due to the mixture of low ignition point substances in the fuel, it will cause the gas mixture to automatically deflagrate before the ignition of the spark plug, forming a new ignition point, and the flame spreads outward at a speed several times higher than the normal combustion, so that the cylinder wall is affected and vibrates, which is called detonation. To put it simply, knocking is a manifestation of abnormal pressure in the combustion chamber caused by abnormal combustion.

A phenomenon when detonation occurs.

The engine will emit a crisp and discontinuous metal knocking sound when a slight knock occurs, while a continuous metal knocking sound will occur when the engine will have a continuous metal knocking sound during a severe and continuous knock, and the engine power will also be significantly reduced.

What are the causes of detonation?

1 The air-fuel ratio is incorrect, and the mixture is too dilute to increase the combustion temperature, thereby increasing the engine temperature.

2. The octane number of fuel is too low, the octane number is an indicator of anti-detonation, the higher the octane number, the stronger the anti-detonation, and the lower the conversely, it is easy to detonation.

3. The cleanliness of the fuel is insufficient, and some physical substances and chemical impurities contained in the fuel, including some aromatic substances, will cause spontaneous combustion and detonation during the compression process of the engine.

4. Excessive carbon deposition in the combustion chamber, due to the serious carbon deposition, the actual volume of the cylinder becomes smaller, the compression ratio increases, and at the same time, the carbon deposition in the high-temperature environment will always burn red due to the poor heat dissipation ability, so that the high-temperature compressed mixture is not only ignited by the sequential spark plug, but also randomly ignited by the high-temperature carbon deposition in the cylinder, resulting in detonation.

5. The engine temperature is too high, the engine is too hot in the environment, the inlet air temperature is too high, or the engine cooling water circulation is poor, which will cause the engine to detonate at high temperature.

6 The ignition angle is too early, so that the piston can gain power as soon as it enters the power stroke after the compression stroke is completed, it is usually ignited before the piston reaches the top dead center. Ignition too early will cause most of the oil and gas to burn when the piston is still compressing the stroke, and the unburned oil and gas will be subjected to great pressure and spontaneous combustion, resulting in detonation.

The methods to solve detonation are as follows.

1. Use fuel that conforms to the compression ratio of the engine.

2. Avoid "drag gear" driving.

3. Regularly clean the carbon deposits and fuel injectors in the oil circuit.

4. Avoid high temperatures: check the coolant water level regularly, check and change the engine oil regularly, avoid long-term intense driving, and monitor the water temperature frequently when driving in summer.

5. Appropriate selection of high-quality fuel additives. For example, fuel additives containing PNF stock solution can solve the problem of engine knocking to a certain extent.

The reason why the car will shake when stepping on the brake may be that the brake disc is ecteriocent, many car owners like to brake in the way of point brake when usually driving, this habit is actually not good, the point brake will cause uneven wear of the brake disc, in layman's terms, the brake disc is high and low on one side. When braking, the brake pad clamps on the uneven brake disc, causing brake shake. The solution to brake shake is to replace the brake disc or polish the brake disc.

In the event of an emergency, the correct way to operate is to press the brakes to the end, and ABS will do the rest. If there is an emergency, the ABS will not be triggered, which may cause danger, and the owner should not brake when driving. During maintenance, we should also pay attention to checking the brake disc and brake pads, and check the thickness of the brake pads, the thickness of the brake disc, and the runout of the brake disc during maintenance.

When the BMW 530 brakes in D gear, the engine shakes, which is likely to be a problem with the engine support (claw glue).

The steering wheel of the BMW 3 Series trembles when braking, because the brake disc is not smooth, and the body will shake when the brakes are stepped on, as long as the brake disc is polished smooth, the brake pad is replaced, or the brake pad is smoothed with coarse sandpaper.

The brakes of the car are indispensable for every car, the vehicle can not be powerful enough, but no one dislikes their own braking performance is good, even if the brake can be less than one meter, it can also save a family invisibly, so the brake is the focus of every car owner, other small problems in weekday maintenance may not care, but the brakes will be repaired.

Brake pads, brake discs.

In the process of using the vehicle, some car owners will encounter, stepping on the brakes always feel that the car is shaking, the vehicle is driving normally there is no problem, once the brakes will be found to be shaking, and this problem is generally the problem of the brake disc.

Why do you shake when you hit the brakes?

Because the brake disc has been deformed in the strict sense, this is going to talk about the dynamic balance, some people have said, I have only heard that the tire has a dynamic balance, what dynamic balance the brake disc wants, in fact, the brake disc is also to be dynamically balanced, but the dynamic balance requirements of the brake disc are stricter than the tires, but the brake disc can not achieve dynamic balance is relatively rare.

Old brake discs. When the brake disc cannot achieve dynamic balance, the brakes will shake when pressed.

Why does the brake disc not move and balance in use?

First, the brake disc is biased, that is, the unilateral wear is serious, this is due to the vehicle body, mainly because the brake pump is not good to return, the car brake is caused by the friction of the brake disc through the extrusion of the brake pump and the brake disc to produce the braking effect, because the brake is only installed in the part connected with the friction plate, when the brake pump brakes after the reset is not complete, it will lead to the aggravation of unilateral wear.

Damaged brake discs.

Second, our usual habits, when the brake disc will produce high heat after continuously stepping on the brake, if you slam on the brake at this time, there is a possibility of destroying the dynamic balance of the brake disc, the brake disc is made of cast iron (pig iron), although its stability is very good, but improper operation will also be deformed.

Third, the use of inferior brake pads, inferior brake pads will contain a large number of metal substances, and after these metal substances are in contact with the brake disc, because these metal substances are relatively hard, the brake pad wears relatively slowly (it itself is to wear) will also reduce the service life of the brake disc.

So once there is brake chatter, what should we do as a driver?

1. Replace the brake disc, which can be determined according to the use of the brake disc, if the brake disc has worn out a lot, it is recommended to replace it together. If the brake disc is less worn, the second can be used.

Second, lathe processing, disassemble the brake disc and hand it over to a professional lathe worker, and the brake disc will be deeply processed, so that it can restore dynamic balance again.

Summary. Hello. We'll be happy to answer for you.

The BMW 5 Series watch hand jumps and the car trembles, and the watch hand jumps because of the unstable idling. There are several reasons for body shaking: 1. Serious carbon deposition in the engine The most common reason for car shaking is that the throttle valve is too dirty or the fuel injector is too much carbon.

2. Ignition system problems Check the working conditions of spark plugs, high-voltage wires and ignition coils, poor ignition system work, and poor spark plug flashing conditions will also lead to this kind of failure. 3. Unstable oil pressure If you have cleaned the engine carbon deposit, washed the throttle, changed the oil pad and spark plug, etc., and still found that the body shakes when idling, it is recommended that you go to the 4S shop to check whether the fuel supply pressure and intake pressure sensor are normal. 4. Aging of engine parts Automobile shake is also related to the aging of engine feet.

Hello. We'll be happy to answer for you. The BMW 5 Series watch hand jumps and the car trembles, and the watch hand jumps because of the unstable idling.

There are several reasons for body shaking: 1. Serious carbon deposition in the engine The most common reason for car jitter is that the throttle valve is too dirty or the fuel injector is too wide. 2. Ignition system problems Check the working conditions of the spark plugs, high-voltage wires and ignition coils, the ignition system is not working well, and the spark plug flashing condition is not good, which will also lead to this kind of failure.

3. Unstable oil pressure If you have cleaned the engine carbon deposits, washed the throttle, changed the oil pad and spark plug, etc., and still found that the body shakes when Soqiaoxiao idle, it is recommended that you go to the 4S shop to check whether the fuel supply pressure and intake pressure sensor are normal. 4. Aging of engine parts Automobile shake is also related to the aging of engine feet.

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The 2019 BMW 5 Series 530Li has traveled about 10,000 kilometers. When braking, it shakes. When the brakes are applied at high speeds, the brake pedal vibrates and creates friction.

What is the reason? By searching online, I found that the problems I encountered were not uncommon, or rather common problems with BMW cars. If you open the link, you will find that most of the problems are caused by the deformation of the brake disc, and the solution is to replace the brake disc.

The day before yesterday was around 1 p.m. the next day, but it wasn't until two o'clock that I was reconfirmed that it was a brake disc and brake disc. The brake disc is free to replace during the warranty period, but the brake pads are consumables, so I have to buy them at my own expense.

There are many people and cars on the weekend, but the car enters the workshop, but it has to queue up to confirm the completion of the project at 2:30 p.m., and the after-sales consultant told me that it is estimated that it will be completed at 5:30

Fast forward. After the maintenance technician tested the car again, confirmed the situation I described, then drove the car to the station and lifted it up for repairs.

Although the shaking can be clearly felt during the test run, the brake disc is a warranty item, and BMW has a set of strict inspection standards, which can only be replaced after reaching the standard.

Before the metering is complete, you have to record it with your camera, attach the instrument to the brake disc, and turn it to capture the amplitude of the pointer swing.

Finally, it was determined that the problem was in the right brake disc, and the pointer swing amplitude was large during rotation, indicating that there was a certain height difference on its surface, but it was difficult to find with the naked eye or hands.