Why the knocking of fingers in the engine and how to fix it

What to do if there is a knocking “fingers” in the engine?

Knocking fingers – this is a common problem faced by many car owners. Let’s talk in detail about what is commonly understood under such a malfunction, how the repair is performed and what will be the cost of the car owner to eliminate the existing malfunction.

Diagnostics of malfunction

Any appearance of extraneous noise of the engine should be a reason for the car owner to carry out a detailed diagnosis of the machine and to eliminate the existing problems. The sooner the car owner turn to the service to perform repairs, the easier and cheaper it is to eliminate such malfunctions.

Such a concept as a knocking of the fingers is not difficult to determine. Of course, there are no fingers inside the engine, and this sound, which resembles, as if the fingers hit the metal engine cover, is caused by improper distribution and subsequent combustion of fuel in the engine. Such sound is formed by the fact that the blast wave from the ignited fuel-air mixture strikes the metal walls, producing a characteristic noise.

When such sounds appear, you should promptly contact the repair shop, as at the initial stage of these malfunctions can be corrected only by adjusting the injection. If the car owner neglects the emerging symptoms of engine malfunction, then eventually the cylinder lining burns out, there are problems with the valve group, and the engine will wait for an expensive overhaul.

The cause of knocking fingers

Regardless of the reason why the fingers start knocking, still such a phenomenon is not normal and it is necessary to open up the engine, perform its diagnosis and appropriate repair. Only on some modifications of engines at a sharp acceleration still such a knock may occur for natural reasons, when the engine is under increased loads. But if such sounds appear at idling or smooth acceleration, then the engine has problems, which should be eliminated as soon as possible.

By the way, the bad quality of the gasoline used can be the cause of such a knocking of the fingers. In no case should you lower the octane number, something the automaker requires. This is the main cause of the unpleasant knocking of the fingers. Such breakdowns can also occur due to a malfunction of the air flow meter or a detonation sensor breakdown. In any case, if the change of fuel did not help to solve the problem, then it will be necessary to initially perform a computer diagnostics of the engine, and then open it up and check the injection.

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Another cause of such problems is ignition system malfunctions. The ignition settings can go astray even in the most modern cars, which leads to improper detonation and the appearance of pronounced extraneous knocking in the work of the engine. In such a case, it is necessary to reset the injector and ignition, which is performed in the service conditions on special equipment.

What is worse, when the cause of the knocking fingers is the general wear and tear of the car. In such a case, a comprehensive repair will be required, which belongs to the category of major repairs and has a corresponding cost. However, this is observed only on heavily worn automobiles, which have run already 300-400 thousand kilometers and more. For such restoration the corresponding repair kits are used, however it is much easier to replace the motor with a second-hand contract one, than to try to restore it.

Let’s summarize.

On most engines, the appearance of a characteristic metallic knocking of the fingers is a sign of malfunction of the ignition system or other engine failures. First of all, the car owner should try to change the fueling, if such did not help, you need to take the car to the service, perform its computer diagnostics, determine the existing faults and conduct prompt repair. It is not advisable to ignore such faults, because later the cylinder lining will be burnt out and there will be problems with the valve group. Eventually, it is necessary to perform an expensive engine overhaul.

What causes the knocking of fingers in the engine

If you were trained in a driving school about 20-30 years ago, you are probably very familiar with such a concept as knocking fingers. It was explained literally at once as soon as the pupil stepped over a threshold of a driving school.

Car engine

But time goes on, technologies improve, new developments are introduced, techniques become more perfect and fail-safe.

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The phrase about clatter of fingers is very common. The only problem is that nowadays it is not quite correctly interpreted. Therefore, it is necessary to understand the true causes and understand how to deal with such situations.

What’s really going on

Before you name the reasons why there are knocking fingers in the engine, you need to get into the essence of this expression.

Old cars really quite often produced an extraneous sound, the provocateur of which were the piston fingers. This was due to the fact that the cars of those times were equipped with metal parts with low strength and resistance to wear during active operation.

The pins were subjected to high temperatures and high loads. All this caused gaps to appear in the piston pin seats. It was because of them that extraneous sounds were formed, which received the fair name of knocking of the fingers.

But if we talk about modern cars, with regard to them, the question of why in the engine during acceleration knocking fingers does not sound quite correct and correct. It’s more a matter of habit and a well-established phrase.

Today’s car manufacturers use high quality steel, use special technologies for processing all components. All this has led to the fact that the probability of a defect and damage to the finger itself is almost completely eliminated. If the pin is deformed on a modern car, you won’t have to think about eliminating the knocking, but about a complete overhaul.

Despite all the changes, the term has not disappeared, and continues to be actively used.

Nowadays, the finger knocking is actually understood as the sound vibrations arising from the shock wave, which is formed by the explosion of the fuel-air mixture inside the combustion chamber. In short, it is engine detonation.

In the case of new cars, finger tapping refers to detonation in the engine.

Regardless of which concept is convenient to apply to the motorist, the problem requires mandatory and urgent intervention. It is necessary to understand how to determine the finger knocking directly in the piston (detonation), and how to cope with the situation.

Detonation in the engine

How detonation is formed

If the engine is running stably and without interruptions, the combustion process of the fuel-air mixture maintains its consistency. The engine functions quietly, no extraneous noises arise. The process starts from the spark from the spark plug side, after which the entire combustion chamber is filled. This occurs equidistantly.

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In the case of detonation or detonation combustion, the process looks different. The entire mixture of fuel and air injected into the chamber is ignited simultaneously. This leads to a sharp and strong increase in cylinder temperature and pressure inside the cylinders. During detonation, the mixture does not burn completely. In the areas where the largest amount of unburned fuel remains, active chemical compounds gradually appear.

If their concentration reaches high levels, a chain reaction may occur, resulting in an explosive ignition. This is in fact an explosion, creating an impressive shock wave. They spread rapidly and crash into the cylinders, the walls of the combustion chamber with great force. In parallel, new areas appear where fuel residues self-ignite.

As a result, vibration occurs, which manifests itself as a strong vibration of the engine.

Mixture ignition in the engine

Causes of internal explosions

Detonation is precisely the root cause of knocking fingers in the internal combustion engine. But in order to eliminate such a malfunction, you need to understand why it occurs.

Here, experts distinguish several reasons:

  • The composition of the mixture. The fuel-air mixture consists of fuel and air, mixed in certain proportions. If the proportions are violated, then oxidative reactions will gradually appear in the combustion chamber, becoming a source of further spontaneous ignition. That very detonation.
  • Ignition advance angle. It has certain values, at which the engine works correctly. If the angle is higher, it will lead to the mixing of the peak pressure. This affects the occurrence of detonation.
  • Octane number. The lower the octane number of the fuel, the more likely the mixture is to explode. A lower octane rating makes the fuel more chemically active and increases its susceptibility to oxidative processes. That is why detonation is much more common in cars that use gasoline type A-76 than in cars with 92 and 95 gasoline.
  • Compression ratio parameters. This indicator reflects the ratio of the volume of one cylinder in the engine relative to the total internal volume of the entire combustion chamber. If the compression ratio increases, then the internal temperature and pressure will increase proportionally. This increases the risk of detonation. For this reason, automobile manufacturers advise that engines with a high compression ratio should only use high-leaded fuel.
  • The glow ignition effect. This ignition provokes spontaneous ignition of the mixture inside the cylinders. It usually occurs when there is a high temperature inside, or when residual soot burns. This is where it is important to choose the right spark plugs. Different glow plugs have different caliber characteristics. They are conventionally divided into cold, warm and medium. Proper selection will not provoke spontaneous combustion and detonation due to overheated insulator of the central electrode.
  • Increased engine loads. Trying to pull an excessive load, overloading the car or starting in 3rd gear and not in 1st, at some point the pins are sure to knock. That is the detonation process will start.
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There are more than enough reasons. And most often, the provocateur of detonation is the motorist himself.

It is necessary to follow the recommendations for the operation of the car, not to overload the engine and service it in time.

This will prevent the conditional knocking of the fingers and protect against the severe consequences of detonation.

Possible consequences

Underestimating the knocking of engine piston pins leads to extremely unpleasant and sometimes very expensive consequences.

Detonation is actually an explosion. It is a destructive phenomenon that can cause failure of elements and components of the power unit. The most severe consequence of spontaneous ignition in the engine manifests itself in the need to overhaul the ICE.

Modern engines, which are constantly running at higher revolutions, are capable of failing in a short time precisely because of detonation.

When the blast hits the inner walls of the cylinder, the integrity of the oil film is broken. The purpose of the oil film is to protect the elements of the cylinder piston group from friction, corrosion and wear. If the film disappears, even for a short time, active mechanical wear occurs. Parts are erased and their correct function is impaired.

In parallel, detonation leads to an increase in engine temperature. And uncharacteristic for the internal combustion engine temperature provokes changes in the performance indicators, destroys pistons, spark plugs, deforms gaskets and seals.

Cylinder failure due to engine detonation

How to eliminate the problem

Not so seldom car owners are faced with situations when, during acceleration, the fingers knock in the engine, implying detonation.

Understanding the causes, the first thing to do is to try to eliminate all possible triggering factors.

Regarding what to do if you notice a knocking engine piston pin, experts give several recommendations. It is not at all necessary to go to the service. Spontaneous explosions do not yet indicate that there are any serious malfunctions in the motor:

  1. If it is a carburetor engine, you should check its condition, as well as the serviceability of the ignition itself. To check the latter, there are years of proven instructions. The car is accelerated to 40 km/h, 4th gear is engaged and the gas pedal is squeezed to the floor. Ideally, the engine detonates for a few more seconds, and then the phenomenon disappears. But if there is no detonation at all, then the carburetor has a late ignition. It is difficult to make adjustments on your own. It is better to go to the service.
  2. Noticing that after refueling on a cold engine for some reason knocking fingers, and at the same time you have just poured new fuel, for sure the reason is in the quality of fuel. It is better to drain it, or go to the services of a proven gas station. Also consider starting with gasoline with a higher octane rating.
  3. Try not to subject the engine to excessive loads at low speeds. If you mainly drive in the city in traffic, it is important to get out at least sometimes on the highway, and actively accelerate the car. This will help to burn off all debris and deposits in the combustion chamber, which act as a provocateur of detonation. A dosed load is only beneficial.
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On modern cars, electronics are actively used, which automatically monitor the combustion processes with sensors, protecting against detonation.

Finger knocking cannot be called an extremely dangerous phenomenon, if it is eliminated at the first signs of its appearance. But you can not leave it without attention. Otherwise, it will lead to serious consequences.

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