The car starts with an abnormal sound, and if it runs fast, it doesn t

There is no abnormal sound at the start, and the reason for this situation may generally be caused by the vehicle's braking system not being in place; There may also be a vehicleSuspension systemAging problems are caused by; The presence of foreign objects in the tires of the vehicle can also cause this to happen; It is also possible that the sound is caused by the resonance of some parts of the vehicle.

Squeak and squeak are only present at idle or low speeds. The reasons for the sound are: the gap between the piston and the cylinder wall is too large; The piston pin assembly is too tight or the connecting rod bearing is assembled too tightly; The gap between the tappet and its guide hole is too large; The profile of the valve cam is worn; Sometimes, the starter grip comes loose and the pulley makes a sound (noticeable when the speed changes).

The sound is disordered when it is maintained at a certain speed, and it makes a brief sound when it decelerates sharply. There are several reasons for the sound: camshafts.

Cracking of the timing gear or loosening of its fixing nut; crankshaft breakage; The piston pin bushing is loose; The axial clearance of the camshaft is too large or its bushing is loose.

The internal gear of the starter loses lubrication, and the phenomenon of astringency and jamming occurs, which affects the timely return of the gear. That is, when the engine is started, the starter rotates to drive the flywheel to rotate, so that the engine starts, and the speed of the engine is driven by the starter, so the engine speed is lower than the starter speed, when the engine starts and the speed is higher than the starter speed, the manual operation ignition switch is powered off and the starter is closed.

When the clutch release bearing is damaged, the clutch plate cannot be completely disengaged, which eventually leads to an abnormal sound during acceleration.

On the issue of abnormal noise of automobiles, it is difficult for ordinary car owners to distinguish which ones are abnormal noises and which ones are reasonable abnormal noises. Only nearly 20% of the vehicles that went to the repair shop to detect abnormal noises really had problems. In the case of a turbocharged engine, there is a must be a difference between the sound and the sound of a naturally aspirated engine; Models with engine guards may also make noises due to friction; After some car owners come into contact with different cars, it is likely that they lack their own understanding of mechanical knowledge, so they can distinguish the abnormal noise of the car and avoid wasting time and energy.

Second, the identification method of car noise:

In practice, due to the limitations of working conditions, it is difficult to measure the sound of the car with special instruments, and the sound of the car can only be described and compared with the judgment of the sound in daily life. For example, the "rattle" sound caused by the dry friction of the bearing, and the "click" sound similar to the small hammer hitting the cement floor caused by the excessive valve clearance.

1. Correctly distinguish between normal and abnormal sounds.

The vibration of each mechanism in the work of the car will emit a variety of sounds, but the sound does not mean that the car is faulty, in order to avoid unnecessary disassembly, we must first distinguish between normal sound and abnormal noise. The normal vibration sound of each system component (such as the noise on the surface of the engine), the impact sound of the gear when shifting, the air intake sound and exhaust sound of using gas as the working source, and the gear meshing noise are all normal sounds. Abnormal noise (abnormal noise) can be divided into slight noise, general noise and malignant noise according to the impact on the performance of the car.

Slight noise, such as the flashover sound of high-voltage electric leakage, the slight loose sound of rolling bearings, etc., the general volume is small, the degree of wear of the parts is not large, and there is no significant change for a long time, and this kind of fault can still maintain the normal operation of the car without repair.

3. When diagnosing abnormal noise, attention should be paid to creating good auscultation conditions and trying to eliminate the interference of other noises, so as not to affect the accuracy of judgment.

It is best to consciously amplify or reduce the sound, that is, use a screw or other metal rod as a stestological instrument to contact the sound part to amplify the sound, or use a single cylinder fire cut-off to reduce the sound to meet the diagnostic needs. The auscultation site should be kept quiet to minimize human interference.

Loose chassis generally occurs in older cars, when the car is driving in bad road conditions, the steering wheel will feel unstable, the bottom of the car will also come out of the abnormal sound, usually the old driver can feel the overall a little loose, when encountering such a situation, it means that the chassis may be loose, and the reasons for this situation are divided into several, only by understanding the reasons, can we better prevent this problem from happening.

The first reason is the aging of rubber parts, we all know that the elasticity of rubber is particularly good, which can buffer the friction between parts and reduce noise at the same time. However, this kind of thing has a lifespan, and it will age after a long time, and the elasticity is not as good as before, so the buffering capacity will decrease, resulting in abnormal noise in each part, so it is necessary to check these rubber parts regularly and replace them in time.

The second possibility is the reason for the shock absorber, the main role of this part is to inhibit **, when the car is driving in the dustpan section, it will have an impact with the road surface, and the shock absorber can well ensure the smoothness of the car, if the shock absorber is damaged, there will be a scoop phenomenon, so that the chassis is loose, so usually check the shock absorber, if there is a leakage to repair in time.

The third is the gap of the parts, that is to say, the ball head may be loose, this part is like the joint of the human body, if the ball head is loose, there will be a large gap between the lever and other connected parts, if the screw will be loose, then the chassis will become loose, so usually check these two parts.

The reason why the chassis creaks when the car is moving:

1. When the car is driving, the chassis makes a creaking sound, which is the MacPherson suspension and shock absorber.

The link between the sections is issued. You can park the car in a relatively quiet place and turn off the engine, press the 4 shock absorbers with both hands, and press the body up and down to make the body shake up and down, and listen carefully in the process of shaking, you can hear which part of the sound is coming from.

2. If the sound is not the sound of the friction between the tire and the ground, it can only be the sound caused by the damage of the outer cage. Replace the outer cage to eliminate squeaky noises. If it is the sound of the tires rubbing against the ground, it is recommended to do a wheel alignment.

3. The creaking sound of the rear wheel may be from the connection between the rear axle and the shock absorber, first check the screws at the connection between the rear axle and the shock absorber to see if there is any looseness.

Car Notes:

1) Before getting into the car, be sure to look around the vehicle to make sure that there is no obstacle to driving safety.

2) When starting, if you feel that the engine power is insufficient and the engine is about to turn off, immediately step on the clutch pedal and start again.

3) The clutch pedal must be carried out according to the essentials of action. If the relaxation is too slow, the contact surface between the clutch friction plate and the pressure plate and the flywheel will wear faster, resulting in damage to the clutch components. The clutch pedal relaxes too quickly. If you press the accelerator pedal too little, it will stall the engine.

4) The refueling of the accelerator pedal should be flexible and gradual. Excessive refueling will cause the car to "spasmodic" forward impulse, which not only affects safety, but also damages the transmission parts of the car. When starting, if you can't get into gear once.

You can release the clutch pedal once and then hang it, or try to put on a different gear before you get in the starting gear.

5) After the car starts, it is not allowed to turn the steering wheel immediately and drive into the middle of the road, and it should gradually enter after confirming the safety.

The above content reference: Encyclopedia - Start.

The reasons for abnormal noise may be: abnormal noise in the body, abnormal noise in the engine, abnormal noise in the gearbox, abnormal noise in tires, abnormal noise in suspension, and abnormal noise in shock absorbers.

1. There is an abnormal sound on the body.

When driving and stepping on the accelerator or brake, there is always some abnormal sound in a certain part of the body, and the sound is not loud. Check whether there are objects in the trunk or rear seat of the car that are not fixed, easy to roll and make sounds, and exclude some items that are not fixed and make noise.

If you find that the friction of the door and window parts of the car causes abnormal noise, you can put rubber strips on the doors and windows or pad rubber on the friction parts, etc., which may be able to reduce or eliminate the abnormal noise, but the result is only a symptom and not a cure.

2. The engine has abnormal noise.

Most people judge by the sound of the sibling** that it is an abnormal sound in the engine compartment, usually a screeching sound of metal or a howling sound. Abnormal engine noise indicates that the technical status of a certain mechanism of the engine has changed. It is mainly caused by excessive wear and tear of some parts or improper assembly and adjustment.

Some abnormal noises can still predict that the engine will be damaged accidentally, so when the engine has abnormal noise, it should be repaired in time to prevent the fault from expanding.

3. There is an abnormal sound in the gearbox.

If there is a "rustle" sound inside the gearbox while the car is driving, and there is no more after pressing the clutch or accelerator, there will be a whistle-like sound when changing gears. There are many transmission parts, and the cause of the sound is also more complicated, whether it is related to a specific speed, such as some are more obvious at about 50km h. Whether it is related to certain gears is very important for judging the transmission failure, and if a gear sounds, it must be related to the components that affect the transmission of that gear.

4. The tires have abnormal noises.

The tires rattle rhythmically, and the faster the speed, the more frequent it becomes. Check whether the tire screws are tightened to rule out the symptoms of abnormal noise. When the hub screws are loose, tap the brakes when going downhill, and the wheels will make a subtle knocking sound, and if the rear wheel screws are loose, the sound of the wheels will be amplified through the trunk, which may be mistaken for something placed in the trunk.

When the hub screw is loose, the wheel will swing when walking, and a more obvious clicking sound will be heard at low speed, at this time, you should stop immediately to check the hub screw.

5. There is abnormal sound in the suspension.

When passing over speed bumps or uneven roads, the suspension noise is very serious, and there are also knocking noises on flat roads. As soon as you encounter a bump, there is a "knock" or "click" sound near the four wheels, which is most likely caused by shock absorber problems or loose suspension parts.

6. The shock absorber has abnormal noise.

The abnormal sound in the direction of hitting in situ may be caused by the problem of rubber parts such as the balance bar, lifting lug and arm rubber sleeve. This sound may be tire noise, each tire will have tire noise, but the time and sound volume are not the same, will not affect the normal use. The toe-in of the front and rear wheels is wrong, causing wavy wear on the tread of the tire, which can also make this abnormal noise.

1. This abnormal noise may be emitted by the braking system. In the southern region, due to the humid and rainy climate in spring and autumn, the brake disc will gradually rust when the vehicle is driven in this environment for a long time.

Especially in vehicles that have been blistered over the chassis, the brake discs are more prone to oxidation and rust. At this time, as long as the rust of the brake disc is rubbed off with sandpaper during maintenance, there will be no abnormal noise.

2. There is an abnormal sound at the start. At this time, the pattern of the wheel may be mixed with the abnormal noise caused by foreign objects, which may be screws, stones or other hard objects, as long as the foreign objects are taken out of the wheel, the abnormal noise problem can be solved. However, if you are stuck with a screw, then you should pay attention to whether the tire pressure has dropped recently, because sharp screws are likely to penetrate the tire and cause the wheel to leak.

3. Chassis reason, which is one of the most common fault phenomena. Many cars will have aging suspension after a certain period of use. At this time, some of the supporting parts in the suspension gradually fail, causing the chassis to make an abnormal noise when the car starts.

You should go to the 4S shop or professional repair factory in time to maintain and inspect the chassis to see if there is loose bearing, aging or oil leakage, etc., and the corresponding accessories should be replaced in time.