There is a knocking sound in the engine when accelerating

Engine problems are a nightmare for any motorist. Therefore, when a knocking occurs in the engine, you should not delay in solving this problem. In this situation, knocking is the impact of parts against each other. This primarily indicates huge ones, which leads to the destruction of mating surfaces.

If you put off visiting a car service center, this may result in worsening the repairs and increasing the cost of repairs. Under no circumstances should you ignore a knocking sound in the engine, but there is also no need to panic ahead of time. The reasons for this phenomenon may be different, and today we will try to understand them.

Why is there a knocking sound in the engine when the speed increases? »

Engine knocking is a nightmare for many car owners. Fortunately, it does not always mean a major overhaul of the internal combustion engine.

A car engine is a rather complex element in its structure, which includes many different systems.

The internal combustion engines of modern cars are technologically advanced and have high efficiency. Each manufacturer introduces its own ideas and technologies there, which are aimed at greater environmental friendliness, lower fuel consumption, and improved dynamics. These technologies may not always be for the good. Sometimes they can cause the owner of this unit a lot of headaches and financial costs, not to mention wasted time and nerves.

Modern motors are very complex, and they are not so easy to repair if they break down. Almost all breakdowns have their own prerequisites, by which one can determine that one or another part will soon fail. We will try to explore these premises.

One of the main prerequisites that says that the internal combustion engine needs to be repaired is the knocking of the internal combustion engine.

Knocking can manifest itself in different ways in different situations. Most often this is expressed when the car is warm, at idle speed, when operating speed increases, when the load is increased and when operating in a cold state.

Causes of knocking in the engine when hot

Low oil pressure.

When idling, a warm engine may make a knocking noise. Most often this is piston knock. This knocking noise is most often associated with low oil pressure. Oil pressure can be low for two reasons.

The piston knocks due to a faulty or clogged oil pump.
The thermal gap in the connecting rod or main bearings has been increased.

As for the oil pump, sometimes flushing the engine helps, but most often only replacement or repair will save you.

If you experience a knocking sound in the engine when it’s hot, and the oil pressure light is flashing at idle, it is recommended not to delay identifying and repairing this problem, because low pressure can lead to oil starvation of the engine.

How to recognize?

Diagnosis of the malfunction should be carried out in the following sequence:

Determine at what point the knocking occurs;
If knocking occurs at high speeds, inspect the gas distribution mechanism and bearings for serviceability;
If you hear a knocking sound at idle, carefully inspect the lubrication system and pay attention to the valve settings.

Only after these procedures can you proceed to a more detailed diagnosis of the causes of the problem.

Causes of knocking in a diesel engine

As a rule, the listed problems can appear not only on gasoline units, but also on diesel ones. However, there is one problem that is unique to diesel power plants - the wrong combustible mixture entering the cylinders. To confirm or refute this assumption, the driver only needs to check the correct settings for the fuel supply to the system.

The video will discuss the reasons for the appearance of knocking when accelerating the engine: Published: February 27, 2020

Car parts that can make this knocking noise

Let's try to figure out what could cause this phenomenon.

You can immediately discard the option of violating the thermal gaps in the timing belt. These knocking noises usually begin at high speeds, then at medium speeds, until the valves begin to knock at idle.

At the same time, the valves do not respond to pressing the gas pedal, that is, if they knock, they knock regardless of whether the pedal is pressed or not.

Also pay attention to the knocking of hydraulic compensators, this is a fairly common occurrence.

Let's start with the most curious reasons.

These can be any cylindrical or round things located in storage boxes, under seats, in the trunk or engine compartment.

For example, the same can of WD-40 can become a headache. For example, this can is under the seat. When it begins to move by inertial force, it rolls along the floor and hits some metal surface.

Also, a foreign object, for example a pebble, may somehow end up in the cabin.

Therefore, when such a nuisance occurs, first of all you need to inspect the interior, put all things out of it and the trunk and check whether the noise has disappeared.

This could also be caused by a loose tank cap or oil filler neck.

Now let's move on to more serious reasons.

The knocking noise may be caused by a damaged door hinge. In this case, it does not fit tightly into the lock and there is some play.

When you press the pedal and accelerate, the door hits the pillar, hence the sound. Therefore, the door hinges, as well as the tightness of its fit, also need to be checked.

There could be worse situations.

Single knocks can also appear due to the suspension.

Here, too, backlash is to blame. It may appear due to worn silent blocks or ball joints.

Checking the suspension for play is relatively simple. The car is placed on the overpass, then a mount is used to check for play by swinging the suspension elements.

Since the suspension connections are quite elastic, it is impossible to swing the levers by hand; this is why a pry bar is needed.

The sound can be made by the tie rod ends, although they seem to have nothing to do with the gas pedal.

But the fact is that the existing play in the tips leads to the fact that the wheel can “float” a little when moving, which causes an impact at the place of play.

Severe wear on the wheel bearing can easily cause a knocking noise.

It's easy to check here. To do this, the front wheel needs to be jacked up.

The first thing you need to do is turn it with force; if you hear any sound from the hub, the bearing is most likely worn out.

Next you need to check the wheel for axial play. To do this, you need to grab the wheel from above and below with your hands and tug; if it moves, the bearing definitely needs to be replaced.

Knocks can also be produced by drive elements.

In some cases, CV joints may make a sound, but this is only when they are slightly worn; severe wear is usually accompanied by a cracking sound when turning.

Worn splines in the drive can also make knocking noises. The culprit, again, is the backlash that forms in the spline joint. When accelerated, it can make an unpleasant sound to the ear.

Steering rack.

In many car models, this device is mounted directly opposite the gas pedal through a metal partition.

If the plastic bushing in which the gear rack runs in the steering rack has worn out, then when you press the accelerator pedal sharply, especially on a rough road, a knock will be heard, which is felt on the gas pedal and radiates to your foot.

It all happens like this - the wheel jumps in the holes, vibrations through the steering rods and silent blocks are transmitted to the steering rack, if the bushing is worn out, the gear rack begins to vibrate in it, making a sound. Vibrations are transmitted to the gas pedal, which is attached to the same wall as the steering rack, only on the driver's side.

Of course, the knock will be heard when you turn the steering wheel.

Also pay attention to the tie rod ends of the same name. They must be firmly fixed with special bolts or nuts.

If you forget to do this for this reason, after installing them or after wheel alignment, knocking noises are possible.

Read about all possible problems with the steering rack here.

The problem may also lie in the differential.

Backlash in its gears can easily cause knocking. Here, identifying the cause of extraneous noise is much more difficult, since it will require removing the gearbox, disassembling it and checking its condition.

We are looking for the cause in the engine mount.

One of the most common reasons for a knocking sound when you press the gas pedal while driving is wear on the engine mount.

Over time, the rubber of the cushion “sags” and loses its elasticity. Because of this, the engine can “jump” on it, hitting the body.

On different cars, the cause of third-party sounds may be different airbags. In some cars, the “drawdown” of the lower cushion causes a knock, in others it is the upper one.

There are several ways to check pillows.

The first and simple one is to open the hood, get into the car, start it, engage first gear and start driving, while watching the engine. If you can’t look after him yourself, you can call an assistant.

If the cushions are worn out, the engine vibration will be significant when starting to move.

The second way is using the same mount and overpass.

The engine itself is just being checked. You need to swing it with a pry bar and watch the pads. If the power plant swings easily, most likely the cushions will have to be changed.

Knocking noise at high speeds.

The reason why a knocking sound appears in the engine at high speeds is detonation. Detonation is the process of combustion of the fuel mixture in the cylinder earlier than expected. As is laid down in the operating principles of any automobile internal combustion engine, all work is based on 4 strokes. Ignition of the fuel must occur strictly at a certain point in time. Sometimes, ignition occurs ahead of time, that is, before a spark appears on the spark plug. At this moment, detonation occurs and, as a result, the engine knocks at high speeds under load.

Piston pins knock: why does this happen?

Let's start with the fact that the knocking of piston pins in an engine can be caused by several reasons. Conventionally, these reasons can be divided into two groups:

mechanical failures;
features of combustion of the fuel-air mixture and load on the power unit;

In the first case, knocking of the piston pins occurs due to wear of the loaded elements. It is also possible that mistakes were made during the repair of the internal combustion engine and installation of new piston pins. If otherwise, the fingers may not be the right size for the seat, or defects may have arisen during their installation. The result is that play occurs at the junction of the piston and the pin and a knock appears. These knocking noises can be easily heard when the engine is cold, and can also knock after warming up. The tapping sound is most clearly heard when the piston is at TDC and BDC.

In the second case, the driver can hear a distinct knocking sound of the piston pins, which occurs only under certain conditions. This phenomenon is called engine detonation and does not mean that there are any mechanical problems in the pin-piston-connecting rod connection. It turns out that your fingers are knocking on an internal combustion engine with a working timing gear. Let's figure it out.

Normally, the piston rises upward, compressing the fuel-air mixture in the cylinder. At the moment of approaching TDC (top dead center), a spark is formed on the spark plug, which ignites the compressed mixture. At the moment when the piston reaches TDC, the mixture burns throughout the entire volume of the combustion chamber. Combustion creates pressure from the expanding gases, which pushes the piston down and thereby performs useful work. The flame front that occurs during combustion of the mixture spreads evenly, that is, the mixture burns. This combustion process of a fuel charge is considered normal.

If we imagine that during the upward stroke of the piston the mixture explodes rather than burns, then the speed of flame propagation increases greatly. The expanding gases press with enormous force on the bottom of the piston, preventing it from rising to TDC. As a result, the piston literally “staggers” in the liner, and the load on the crankshaft, including the piston pins, increases significantly. The driver hears a distinct metallic knock in the engine precisely at such moments, as the gas pressure in the cylinder increases greatly. At the same time, the engine power decreases, the engine begins to smoke and vibrate, and the temperature of the power unit rises. Note that detonation can occur in both gasoline and diesel engines.

Such an abnormal combustion process of the mixture destroys the internal combustion engine, leads to burnout of the pistons, breaks piston rings, etc. The consequences of detonation can be very serious, as engine parts experience a significant increase in load and are destroyed. Defects occur both at the bottom of the piston and at its head. The shock wave from the explosion of the fuel charge knocks down the oil film on the cylinder walls, resulting in wear of both the rings and the cylinder walls themselves. Vibrations from detonation combustion cause destruction of connecting rod bearings (liners); defects arise in the area of the partitions that are present between the piston rings. In a word, detonation can significantly reduce the life of any internal combustion engine.

Due to detonation, the fingers briefly knock during acceleration. This especially often manifests itself when the driver tries to accelerate while driving, for example, uphill, while remaining in a higher gear. This type of detonation is called finger knocking when driving under tension. In order not to overload the engine, it is necessary to promptly switch to the gear that corresponds to the driving conditions. All this depends only on the driver. In parallel with this, there are several other reasons why fingers begin to tap.

Why does the engine knock when hot?

The appearance of knocking during engine operation is caused by a critical decrease in the size of the working gaps between parts inside the engine. When the engine is cold, the oil in it is in a thick state, and the metal of the parts does not expand. However, as the engine temperature increases, the oil in it becomes thinner, and the gap between the worn ones leads to knocking. So, the reasons why the engine knocks when hot can be:

Insufficient oil level . Under such conditions, the rubbing pairs will work without lubrication. As a result, premature wear occurs and knocking sounds appear.
Crankshaft and its bearings . The connecting rod and main bearings are made of a softer metal than the crankshaft itself, so as a result of poor lubrication or service life, the surfaces wear out. At the same time, they can turn and knock.
valves _ Most often this occurs due to wear on the valve rocker or because the camshaft oil passage is clogged.
Hydraulic compensators . They most often knock due to low oil level or insufficient oil pressure. They may also wear out.
Phase shifters . In an engine with a chain or belt drive whose mileage exceeds 150...200 thousand kilometers, wear of internal parts or coking of oil channels occurs.
Pistons and cylinder walls . As the engine wears out, the geometry of the pistons is disrupted. In addition, damage to the piston rings and piston pin is possible.
Crankshaft bearing . It wears out naturally or may be installed incorrectly during repair work.
Detonation . The sounds of detonation are reminiscent of dull explosions in the engine cylinders, which occur due to the fact that the fuel ignites sharply rather than smoothly.

More detailed information about these causes of knocking when hot, as well as their subtleties and repair methods is written below.

Low oil level

This is one of the most common reasons why a knock appears on a hot engine. Cold motor oil is more viscous, and as the temperature increases, it thins out and often acts as a damper through which metal parts interact and make various knocking sounds. If the oil level is insufficient, the parts will interact “dry”, making clanging metallic sounds. As the engine warms up, the oil dilutes and does not soften impacts between worn parts as much as possible, which is the source of knocking in the engine when it is hot.

There is usually a loud clanging sound that occurs in a variety of operating modes, but it intensifies as the load on the engine increases and it warms up, that is, “hot”. In fact, a low level of engine oil is very harmful to the engine, so the lubricating fluid must be either topped up to the required level or completely replaced with a new one along with the oil filter.

Crankshaft and bearings

The crankshaft has so-called “cranks”, which almost never lift up, since they are made of very durable metal. The main bearings are installed into the block, and the connecting rod bearings are installed directly into the connecting rod, and this design fits onto the crankshaft. And accordingly, when the bearings (usually connecting rod bearings) wear out, a clanging knock begins to appear on them.

Moreover, these sounds are reproduced precisely when it is hot , since in this state the metal expands, and the metal of the liners is much softer than the one from which the crankshaft is made. This can lead to the fact that any one (or even several) bearings may rotate and collide with the bearing facing it on the shaft. As a result, the connecting rod and piston may simply jam. One option is the “fist of friendship”, when the piston breaks the cylinder block and comes out, which often occurs when water gets into the combustion chamber.

The maximum allowable gap will differ for different motors, but on average it is about 0.07 mm. After this, urgent repairs are needed! Wear of the liners is caused by insufficient oil level, carbon deposits, water, engine overheating, and frequent high engine speeds.

Incorrectly adjusted valves

With increasing load on the engine, the valves make clicking sounds. This is especially true for old cars, like VAZ classics, Muscovites and other Soviet cars. The valves usually click when the engine load increases and the engine oil level is low.

Causes of valve knocking:

wear of the camshaft housing;
wear of the valve rocker (another name for rocker is rocker arm);
clogging of the oil channel in the camshaft, through which oil is supplied to the valve rocker.

The main reason for valve knocking is an unadjusted gap between the levers and the camshaft cams. As the gap increases, the cam will knock on the rocker arm, as a result of which a pronounced metallic knock will appear, repeated in time with the rotation of the camshaft . On average, the valves need to be adjusted approximately every 10...15 thousand kilometers.

Even if the oil level in the engine is insufficient, the valves may not knock at idle speed without load. However, when accelerating, if there is not enough oil, you will hear a distinct metallic sound that repeats frequently. And if the engine has hydraulic compensators that adjust the gap automatically, then they will often be the cause of knocking in the internal combustion engine when it is hot.

Hydraulic compensators

The reason for knocking sounds when the engine is running hot can also be the knocking of hydraulic compensators when it is hot. In turn, the reason for their knocking may be:

low oil level in the engine crankcase;
clogged oil filter;
incorrectly selected oil;
problems with the oil pump;
disruption of oil viscosity by additional additives;
problems in the operation of the plunger pair of hydraulic compensators.

Most often, the problem with knocking hydraulic lifters can be solved by simply replacing the oil and oil filter.

Phase shifters (vvt-i, cvvt, vanos)

Phase shifters can also make clicking sounds when they're hot. When cold, the oil in their bridges has a high viscosity, and as it warms up, it thins out. Phase shifters are capable of “clicking” in a variety of engine operating modes - at idle, during acceleration, under load. Also, such a clutch can produce knocking and rattling noise due to significant carbon deposits that impair the functioning of internal parts.

When phase shifters partially break, they produce unpleasant sounds even with significant wear. The average wear mileage is at least 150...200 thousand kilometers. You can extend the life of the vvt-i coupling by using high-quality motor oil, as well as gentle engine operation.

Knock of piston pins: fuel, ignition and internal combustion engine temperature

As already mentioned, the piston is attached to the connecting rod using a piston pin, and it is necessary to realize the possibility of movement of the piston in relation to the connecting rod. The occurrence of increased loads leads to the fact that the fingers knock in the seats. If everything is in order with the crankshaft on the engine, then the main culprit is detonation.

Fuel in the cylinders may begin to detonate:

as a result of general or local overheating of the motor;
if there are problems with the composition of the mixture;
refueling with gasoline with an octane rating that is inappropriate for a given internal combustion engine leads to detonation;
if the ignition timing (IAF) is too early, then detonation also occurs;
malfunctions of the ECM sensors (DPKV, coolant temperature sensor, knock sensor) can lead to explosive combustion of the mixture in the cylinders;

It should be borne in mind that engine detonation may well occur even on a new engine. If the temperature of the unit is normal and there are no problems with the operation of the cooling system, then the possibility of refueling with unsuitable fuel should be ruled out. Next, you need to start checking the ignition, mixture quality and electronic sensors of the internal combustion engine control system (on units with an injector).

Engine knocking when cold.

If this symptom is observed on a car, it means that some thermal clearances are broken.

Camshaft knocking

A knock in the engine when cold will appear in the first seconds of operation when there is significant wear on the camshaft.

As oil gets onto the camshaft, the knocking noise will become less and eventually disappear altogether. With severe wear, the knocking noise can continue for quite a long time, and will stop only after warming up. Locally it can be heard at the top of the engine.

The main reasons for engine knocking due to camshaft wear:

Poor quality oil
Late oil change
Oil fasting
Presence of harmful additives

If the camshaft is worn out, there is a high probability of reduced compression in the engine, this is especially true for engines equipped with hydraulic compensators.

Based on the signs described above, one can only indirectly assume that the camshaft is not in order. In order to find out more accurately, you need to remove the top engine cover and visually inspect and check for wear on the camshaft.

Crankshaft faulty

This symptom is no longer so joyful. If the camshaft can be replaced without any problems without removing the engine, then most likely you will need to do a major overhaul.

The fact is that a dull knock of the engine when cold most often indicates that it is a knock of the crankshaft and it probably has wear. The crankshaft bearings, or maybe the crankshaft itself, can knock due to increased thermal clearances in the main and connecting rod bearings. It is also possible to hear a knocking sound from the connecting rod whose bearings have turned.

If in the first case it will be possible to replace the bearings, then if the connecting rod is knocking the consequences can be more serious, and if it starts, you can end up with boring or replacing the crankshaft.

It is important to note that when any knocking occurs in the internal combustion engine, it is imperative to carry out a comprehensive diagnosis and find out the cause. Otherwise, you can end up paying a large sum of money for repairing the internal combustion engine or replacing it.

Causes

When the power unit operates correctly, the sequence of the fuel combustion process is maintained. It starts from the spark plugs, and then fills the entire chamber equidistantly. Detonation combustion occurs in a completely different way. The entire volume of the fuel-air mixture explodes simultaneously, sharply, provoking a significant increase in the pressure and temperature of the cylinders themselves. Under such conditions, chemically active compounds are formed in places of the highest concentration of unburned fuel. When critical values are reached, chemical chain reactions occur that promote explosive ignition. The resulting wave moves quite quickly, strongly impacts the walls of the chamber and the surfaces of the cylinders, and at the same time new points of spontaneous combustion are organized. The result is numerous oscillatory phenomena that provoke vibrations of the power unit.

This phenomenon is detonation, which becomes the root cause of why the fingers knock in the engine. It can occur for various reasons, the most common are: Fuel composition. If air and fuel are in a 9-0 ratio, which violates the average, then in the event of penetration into a chamber with elevated temperature and pressure, various oxidative reactions are formed in remote areas, which are the primary source of the process of self-ignition, that is, detonation. The magnitude of the ignition timing. An increase in this indicator provokes a shift in the maximum pressure peak, which becomes a factor in the occurrence of detonation processes. Octane number of the fuel mixture. The lower this indicator, the greater the likelihood of detonation. A decrease in this criterion leads to an increase in the chemical activity of the fuel to the oxidation process. Therefore, car owners using 76-octane gasoline notice the knocking of the piston pins much more often than drivers who fill the tank with 92-octane gasoline. Compression ratio. An indicator characterizing the ratio of the volume of one cylinder to the total volume of the combustion chamber. Its increase leads to the fact that pressure and temperature invariably begin to increase, which means that the risk of detonation increases. Therefore, if a power unit with a sufficiently high compression ratio is installed, then the car owner is recommended to use high-leaded gasoline. Glow ignition, which causes spontaneous combustion of the fuel mixture in the cylinders. Occurs due to the presence of burning soot or high temperature in the chamber. It is equally important to choose the type of spark plug correctly. There are “cold”, “warm” and “medium” candles, characterized by different heat indicators. This is necessary so as not to cause a fire if the insulator of the central electrode of the spark plug overheats. Increased load on the motor. If the driver tries to start every time, for example, from third gear, then at some point he will invariably hear the fingers of his engine knocking.

Why does a gasoline engine knock when accelerating?

The most commonly reported problem occurs on vehicles that use a chain-driven motor. A fairly common problem is when it is the chain that causes knocking noises when accelerating. The situation is that the chain is stretched during operation, and when the speed increases, it begins to touch the block body, which is why noise occurs. This rumble is especially audible when the car picks up speed, but this knock is actually present in all modes. Accordingly, to determine whether this malfunction is the cause of the problem, you need to check the chain tension. If it is loose, the chain will need to be tightened or replaced.

Depending on which part of the engine the noise comes from when accelerating, the problems that lead to this vary. If you hear noise from the top of the engine, it is usually due to wear on the camshaft. Depending on the number of revolutions, the intensity of the noise will change. This is why drivers most often pay attention to a knocking sound during acceleration when this problem exists. If the camshaft is actually faulty, you will need to dismantle it and replace the failed shaft.

Please note: Most often the malfunction is associated with a problem in the bearings.

Another cause of noise during acceleration is the pump. In fact, in this case it is not the engine itself that is knocking, but since it is located in close proximity to it, the driver may confuse these noises. Most often, the pump makes noise due to the destruction of the bearing. Moreover, the higher the vehicle speed, the louder the noise. Often, even experienced specialists are not able to say for sure whether the pump or the camshaft is knocking. To finally determine the problem, you need to remove the water pump, and then try to manually turn the part. If you hear knocking noises when turning the pump, this indicates the need to replace it or try to repair it.

If the engine knocks not only during acceleration, but also when low speeds are maintained, the problem is most likely due to insufficient oil in the engine. It also cannot be ruled out that the oil used, if there is enough of it, is of low quality and does not cope with its tasks. As you know, the task of oil in a car engine is to create a thin protective layer on the parts. If it is not created, the engine will knock noticeably at high speeds.

Other causes of engine knocking

Faulty hydraulic compensators. This device is designed to adjust the thermal gap between the camshaft cam and the valve tappet using oil pressure. Often hydraulic compensators fail and begin to knock. They can knock in the engine when it is cold or when it is hot.
Malfunction of the variable valve timing system. On various cars, this system very often blows the minds of its owners (for example, the legendary BMW Vanos).
Knock of attachments. There may be a knock or even a whistle from any engine attachment. For example, a pump, or an air conditioning compressor, or a roller tensioner.

EGR valve. On some cars, when cold, you can hear the EGR valve rattling. As a rule, this is not critical.
Stretched chain. Engine knocking at idle speed will occur when the chain is stretched. The main advantage of a chain over a timing belt is its durability. But that doesn't mean she can walk forever. On some branded foreign cars (mostly German), the chain can stretch to 50-60 thousand kilometers. If the chain is stretched, it will also make a metallic knock; if the engine is gasoline, then with a stretched chain, its operation will be similar to that of a diesel engine.

These are not all the reasons for engine knocking, because now each manufacturer makes an engine using its own technology, which is not without drawbacks and if they are not taken into account, they can add a lot of headaches to the owner.

In general, we can draw a conclusion. Any gap whose geometry has been disrupted due to wear and tear can cause some kind of knocking noise in the engine during operation.

How to determine why the engine knocks during acceleration

As you can see, there are many reasons that can lead to engine knocking during operation or acceleration. And not all variants of such a malfunction were listed above. For example, knocking when the engine is running can be caused by such things as an unscrewed sump guard, the knock from which comes from approximately the same place where the crankshaft knock can be heard, which is why they are often confused.

To diagnose what exactly is causing the engine knocking during acceleration, you first need to determine when exactly the noise occurs. There are 3 options:

The knocking sound is heard all the time when the car engine is running. In most cases, this is due to wear on the crankshaft or crank mechanism, if we ignore simpler reasons;

Engine knocking appears only at high speeds. This problem often occurs due to a malfunction of the gas distribution mechanism and wear of the bearings that are part of the motor structure;
Engine knocking is only heard at idle. The cause should be sought in the lubrication system or valve settings.

Having decided on one of these three options, you can move on to a more detailed search for the cause of the malfunction.

( 438 votes, average: 4.61 out of 5)

Engine decarbonization: instructions, recommendations, choice of decoking agent

Engine speed does not drop at idle

Detonation and knocking of fingers in the engine: causes and solutions

Many motorists are concerned about the question, why do the fingers knock in the engine when accelerating the car? It is worth saying that the formulation of this question is initially incorrect.

Although the phrase “knock fingers” itself is very common, it is still incorrect. Piston pins cannot knock, but in fact we hear the sound of a shock wave of exploding fuel.

Fuel combustion in a working engine occurs sequentially. Starting near the spark plug, the flame gradually occupies the entire combustion chamber.

However, there is another type of combustion called detonation. During this phenomenon, the entire fuel-air mixture in the combustion chamber explodes sharply, while the pressure and temperature in the engine cylinder increases significantly. Such an explosion is called detonation. And the knock from this explosion is the answer to the question of why the fingers knock in the engine.

There is also the concept of engine vibration, which is often confused with detonation. If detonation is associated with fuel combustion, then vibration is the process of vibration of the power unit caused by a malfunction of its installation.