Translated from English, EGR means “exhaust gas recirculation”. Some of the exhaust gases are returned back to the cylinders for final combustion.

What is an egr valve for?

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Due to the action of EGR from exhaust manifold some of the exhaust gases are returned to intake manifold. Thanks to this function, exhaust toxicity is significantly reduced during engine warm-up, as well as during sharp acceleration. In these two modes, the engine runs rich fuel mixture.

The EGR system consists of several parts. The central part is the valve itself. Often, due to a violation of the tightness, its malfunction occurs. In addition, being in constant contact with hot gases also does not contribute to particular durability. The second part is the EGR solenoid. It is used in systems where the valve is controlled pneumatically.

The third element of the system is the EGR valve stem position sensor (also known as the EGR valve opening degree sensor). It happens that it malfunctions, but this does not cause much trouble. Unless the engine fault light comes on. Finally, the last part is the engine control unit.

Operating principle of the EGR valve

The mechanism of operation of the system is based on returning part of the exhaust gases back to the intake manifold. This process happens over a certain period of time. Then the exhaust gases re-enter the engine, but with a fresh mixture. All this is determined by the control unit in which a special program is installed.

The recirculation system functions only when the engine warms up to fifty to sixty degrees. After the engine reaches 1000 rpm or more, the recirculation system starts working and operates until the engine reaches 4000 rpm.

The EGR system does not function when high speed movement of the vehicle and during acceleration, since at this time the engine is running at full power and there is no need to reduce the concentration of nitrogen oxide in the exhaust gases. The recirculation system is used most actively when the vehicle is moving at speeds from 50 to 120 km/h.

The recirculation system allows the car owner to save fuel consumption. This is achieved by depleting the combustible mixture: when the system is put into operation, a certain program is automatically launched. This process of functioning is controlled.

One of the practice-tested recommendations is to mute egr valve. In this case, the engine will operate reliably and no problems will arise. In addition, it is desirable that the tachometer needle does not remain for a long time in the range below two thousand revolutions. This will prevent soot from forming in the intake manifold.

EGR system malfunction

EGR valve from Toyota Rav 4

Valve leakage affects engine performance. IN general case the normal combustion process of the fuel mixture in the cylinders is disrupted. This happens due to a decrease in the volume of oxygen contained in the air that enters the engine. Important role V in this case Other factors also play a role: the amount of exhaust gases entering the intake manifold, general state and engine speed.

Any engine control unit has a speed stabilization program. If such stabilization is successfully achieved, an increase in speed leads to an increase in pressure in the exhaust manifold. An increased amount of exhaust gases, which are poorly enriched with oxygen, begins to enter the intake manifold. All this leads to instability of the engine itself.

Causes and symptoms of egr valve malfunction

There are two main causes of malfunctions:

• small volume of exhaust gases passing through the recirculation system valve;
• too much exhaust gas passing through the system valve.

As a result of uneven settling of solid particles from the exhaust gases, the EGR valve begins to close loosely. In this case, it must be cleaned and installed in its original place, but before this it is necessary to free the channels from the effects of sedimentation of solid particles. If this is not done, the valve may become clogged again.

Restoring normal operation

Initially, the EGR system is designed for a vehicle mileage of no more than eighty to one hundred thousand kilometers. After this, it is necessary to replace all components of the system. IN domestic conditions A complete replacement after 50,000 km is optimal. However, in practice, this is not something everyone can afford. In this case, timely service can be recommended.

The seat and stem must be thoroughly cleaned to ensure tight closure and smooth operation. Sold in aerosol packaging special liquid

, used to clean the carburetor, is effective in this case. In this case, this liquid must not be allowed to come into contact with the diaphragm.

If there is a solenoid, you need to clean the small filter located in it. This device is designed to protect the vacuum system from dirt. After cleaning this filter, in many cases the problem disappears.

Often, after a valve failure, car enthusiasts try to turn it off. This is usually done using a gasket cut from thin tin. There is no need to cut holes for the passage of gases. Only if the rod protrudes beyond the seating plane is it necessary to make a hole.

Thus, the EGR valve is of great importance in the normal functioning of the recirculation system.

The exhaust gas recirculation (EGR) system, better known by the abbreviation EGR or EGR (from English: EGR - Exhaust Gas Recirculation), is designed to increase engine efficiency and make emissions more environmentally friendly. Among other things, the USR reduces vibration on a diesel engine and does not give a chance on a gasoline engine. The system is not new and has been used for a long time; it could be found even on old domestic cars

, however, due to an imperfect design and the lack of specialists capable of repairing the exhaust gas recirculation system if something happened, it was usually removed, that is, deactivated using various methods.

Exhaust gas recirculation system - purpose

You all know that in the combustion chamber during engine operation, the temperature reaches a high level, as a result of which oxygen reacts with nitrogen, resulting in the formation of nitrogen oxide. Due to the lack of oxygen, which is necessary for burning the fuel mixture, and an excess of nitrogen, the fuel is burned with less efficiency. As a result, engine efficiency (power) decreases, and fuel consumption increases. In addition, due to poor combustion of fuel assemblies, the environmental friendliness of emissions decreases and the level of harmful CO and HC in the exhaust gases increases.

The role of the EGR valve in the recirculation system

The main role in the system is played by the EGR valve, since it is it that allows the exhaust gases to return to the intake manifold, mix with a fresh portion of air and “burn out,” thereby reducing the toxicity of the exhaust. Thanks to oxygen, the combustion temperature increases, but due to the release of a certain amount of exhaust gases, the oxygen content decreases to the required level. As a result, the level of harmful emissions is reduced, and the combustion temperature is also lowered to the optimum, while significant fuel savings are observed.

The EGR valve also allows you to minimize or completely avoid pressure drops across the throttle valve resulting from pumping losses. Due to lower combustion temperatures of fuel assemblies, detonation is reduced, which makes it possible to set an earlier ignition point. In turn, this improves engine response and increases engine torque. There is also a positive effect of the EGR valve; due to a decrease in the amount of oxygen, combustion pressure decreases, as a result, engine operation at idle becomes smoother.

How does the EGR valve work?

The operation of the EGR valve differs depending on the type power unit. In engines running on heavy fuel, the valve opens at idle speed, which ensures the intake of about 50% of air. During operation, the EGR valve closes depending on the load. IN gasoline engines At idle, the USR is closed, and under load the valve opens, which allows air intake by approximately 5-10%.

In most cases, the exhaust gas recirculation system is a closed loop. A slightly less common system is electrically controlled EGR, as well as a position sensor that sends a signal to the ECU. The remaining systems have electro-pneumatic adjustment, in which Feedback implemented through sensor correction mass flow air (), as well as sensor absolute pressure in the intake manifold (MAP) or using the intake air temperature sensor.

EGR valve malfunctions

The most popular problem that occurs with most motorists is carbon deposits that concentrate on the EGR valve seat or plate.

There may be several reasons for this unpleasant phenomenon:

• For example, this may be due to a poor-quality dirty intake mixture;
• Malfunctions in the operation of the air flow meter (MAF);
• The problem may also be clogged crankcase ventilation ducts;
• Ineffective combustion of fuel assemblies, as a result of which dirty residues along with carbon deposits circulate through the EGR valve and contaminate it;
• in the engine;
• Serious wear on the cylinder piston group;
• Failure or critical wear of injectors, which disrupts the accuracy of fuel injection.

Signs of a malfunctioning EGR valve

A faulty EGR valve, as a rule, sticks in the open or closed state; it also happens that the valve sticks gradually, operating late or periodically.

• The valve is stuck in open state. In this case, the gasoline engine will idle intermittently; a diesel engine, as a rule, will experience a decrease in traction and the appearance of black smoke from the exhaust.
• The valve is stuck closed. In this situation, the “work” of the diesel engine will worsen, and it will begin to “dieselize” even more, that is, to vibrate and make noise. Gasoline engines, as a rule, become inefficient, their fuel consumption increases and their dynamics deteriorate.
• The valve slows down or operates late. Such disturbances in the operation of the EGR system are less noticeable and sometimes it is very difficult to determine that something is not working correctly. However, problems are mainly observed at idle speed, and in some situations the corresponding malfunction indicator (MIL or CHECK) lights up on the panel, which indicates problems with or.

Solution

The problem with the USR can be solved in different ways. For example, USR cleaning in case of contamination, it will allow the engine to return to stable operation and dynamics, however, if the valve is clogged with deposits, one should look for the cause of this phenomenon, and not eliminate its consequences.

In some cases, motorists decide to turn off the USR in an attempt to solve this problem once and for all. The USR plug is performed in cases where purchasing a new valve is impractical or unprofitable, in the case of engine tuning (), as well as in cases where the CPG has suffered serious damage and there is too much in the exhaust large percentage oils In some cases, usually on older engines, removing the EGR valve actually solves the problem of speed and dynamics, but the effect is short-lived and after some time the problem returns again.

How to disable the EGR (shut off the EGR valve)?

On old cars that were produced before 2000, remove this valve- a couple of trifles. All you need to do is turn off its power. On more advanced engines, the well-known “CHECK ENGINE”, which everyone is so afraid of, can be observed. In this case the best solution will plug the tubes that go to the valve; such an upgrade will not cause failures, but will solve the problem.

Disabling the EGR system on vehicles older than 2005 can cause big problems. The valve is also often silenced during the “chipping” procedure, as a result the engine becomes more playful and productive.

As an option, some motors provide the possibility of reflashing the “brains” (ECU), after which the motor can safely operate without a USR, and no mechanical or electrical interventions in the operation of the engine are required.

There are many options for how to silence the USR, but each of them has its own pros and cons, and also requires certain skills, so before taking on this work, study the issue thoroughly, since there are a lot of photo reports on the Internet on how to do it correctly, or just trust the specialists.

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As is known, the most toxic components of car exhaust gases are hydrocarbons, carbon oxides and nitrogen oxides. Deals with the first two quite effectively catalytic converter, nitrogen oxides are not “screened out” enough for them. To reduce harmful emissions of nitrogen oxides, EGR (Exhaust Gas Recirculation) was created - an exhaust gas recirculation system. It is not intended to improve technical characteristics motor, and is installed solely for environmental reasons.

The idea is to supply some of the exhaust gases from the exhaust manifold to the intake manifold at certain engine operating conditions. An increased content of nitrogen oxides in internal combustion engine emissions is caused by high temperatures in the combustion chamber. The catalyst for the combustion reaction is oxygen: the more oxygen, the higher the temperature. And if you mix it with air traffic fumes, then the oxygen content in it will decrease. As a result, the combustion temperature of the mixture and, accordingly, the toxicity of exhaust gases are reduced.

EGR is installed on both gasoline (except turbocharged) and diesel engines. Due to excess air in a diesel engine, more nitrogen oxides are formed. In addition to improved environmental performance (NOx emissions are reduced by up to 50%), there are some other positive side effects. In gasoline engines, a portion of exhaust gases, reducing the vacuum in the intake manifold, reduces pumping losses, which helps reduce fuel consumption by 2-3%. Operating at low temperatures gasoline engines reduces the risk of detonation, and operation diesel engines becomes softer. Soot emissions from diesel engines with an EGR system are reduced by 10%.

The EGR operating algorithm depends on the engine type. In diesel engines, the valve opens at idle and supplies up to 50% of the intake air volume. As the speed increases, the valve closes proportionally until it is completely closed at maximum load. When the engine warms up, the valve is also completely closed. In gasoline engines, EGR does not turn on when the engine is cold, at idle speed, or at maximum torque speed. At low and medium loads, the system provides 5-10% of the air supplied to the intake.

It is worth noting that EGR often turns into headache for our motorists. The system is quite capricious during its operation (especially on domestic fuel) the EGR valve, intake manifold and sensors located in it become covered with carbon deposits, which leads to unstable engine operation. The EGR valve is an expensive part, so many car owners, instead of replacing it, resort to shutting down the entire system.

Why is EGR not installed on gasoline turbo engines? On naturally aspirated engines The system works almost only at medium speeds. And on turbocharged engines the operating range is even smaller - and it turns out that the end does not justify the means. Therefore, manufacturers use other methods to reduce NOx emissions: liquid cooling charge air(which reduces the temperature in the combustion chamber) and a continuously variable valve timing system (providing internal exhaust gas recirculation). With internal recirculation, part of the exhaust gases returns to the cylinder at the moments of valve overlap, when both the intake and exhaust valves are open at the same time. Technically, overlap can also be organized by selecting the shape of the camshaft cams, but in this case, recirculation will be carried out in all engine operating modes. In stepless control systems, valves close at the command of the control unit only in the required modes.

Types of structures

Although the operating principle of all systems is the same, their design differs great variety. In any EGR system, the main part is the valve. The differences lie in the way its operation is controlled and, accordingly, the composition of the elements. EGR first appeared on American cars back in the early 70s of the last century. They were pneumomechanical, that is, they were controlled only by the vacuum of the intake manifold. Like any mechanical system, it was not distinguished by high accuracy of work. With the introduction of electronic engine control systems, EGRs became electro-pneumatic (Euro-2 and -3), and later fully electronic ones appeared (Euro-4 and -5).

The EGR valve can be installed on the intake manifold, in the intake tract, or directly on the throttle body. Since in diesel engines The EGR system bypasses a larger amount of exhaust gases, and the valves in such systems have a bypass hole of a larger diameter compared to gasoline ones. In some diesel engines, especially turbocharged ones, the intake pressure can exceed the exhaust pressure, making exhaust gas recirculation impossible. In such cases, to create the necessary reduced pressure in inlet pipe regulating (vortex) dampers are installed.

In pneumomechanical systems the valve is held closed by a spring. When a vacuum is applied to the vacuum cavity, the membrane overcomes the resistance of the spring and opens the valve. Exhaust gases pass through the channel into the throttle zone of the intake manifold. The EGR valve pipe is connected to the intake manifold in the area throttle valve. At idle and when braking, the throttle valve is closed, there is practically no vacuum above the valve, and the EGR valve is closed. At average engine loads, the throttle valve is slightly open, and since a vacuum occurs underneath it, the EGR valve opens. At full power, the throttle valve is open, the vacuum in the throttle valve area is weak, the EGR valve will be closed.

In electro-pneumatic systems The operation of the valve is controlled by the engine controller based on sensor readings. Depending on which sensor is the main one, four types of systems are distinguished:

• with exhaust gas backpressure sensor;
• with exhaust gas temperature sensor;
• with EGR valve position sensor;
• with an MAP intake pressure sensor (or MAF mass air flow sensor) together with an oxygen sensor (lambda probe).

In addition, other sensors of the engine management system are used, for example: throttle position sensor, coolant temperature sensor, etc. different engines The composition of the sensors may change. ECU in the right moments supplies control signals to the solenoid valve, which connects or disconnects the vacuum source to the EGR pneumatic valve. The solenoid valve has only two positions: open and closed. More advanced systems use an electro-pneumatic converter, which provides smooth control of the degree of recirculation. Some EGR designs may use a vacuum pump to create vacuum.

IN electronic systems The EGR valve is controlled directly by the engine control unit without the use of vacuum. There are two main designs of digital EGR valves: with three or two different-sized holes. The holes are closed by solenoids in different combinations. With three holes you can get 7 different levels of recirculation, with two holes you can get three levels. Even more advanced is the valve, the degree of opening of which is determined by the ECU through stepper motor. This results in smooth regulation of the exhaust gas flow.

On some engines, the EGR system uses additional cooling gases To do this, the recirculation valve is turned on regular system cooling. This measure allows to further reduce the emission of nitrogen oxides.

Malfunctions and maintenance

Over time details EGR systems Even in a working engine they become covered with carbon deposits. Diesel engines are more susceptible to this phenomenon due to the soot contained in their “exhaust”. Frequent travel over short distances accelerates the pollution process. And in faulty engine it intensifies many times over. The reasons may be the use of low-quality fuel, malfunctions in the power system, general engine wear, increased oil content in intake tract. Excess oil appears when there is a malfunction in the crankcase ventilation system, worn valve stem seals or valve guides, turbocharger malfunctions (bearing wear, clogged oil drain line), too high an oil level, or the use of oil that does not match the engine.

The EGR valve is the first to suffer from carbon deposits. Carbon deposits prevent the valve from closing tightly and impair the mobility of the stem. Ultimately, the valve gets stuck in some position, which leads to problems with the engine. These violations manifest themselves in different ways, depending on the position in which the valve is stuck. In addition, the consequences of a stuck valve vary depending on the type of engine and the design features of the EGR system itself. Most often, malfunctions of the EGR system lead to uneven idling (floating speed, low or high speed) and the engine often stalls. You may also experience jerking and popping noises in the muffler during acceleration, jerking and popping noises at the intake when you drop the speed, a drop in power, and difficult starting. Gasoline engines experience detonation and misfires, while diesel engines become “hard”. On turbodiesel engines a non-closing EGR valve reduces turbine performance. On some vehicles, the control unit switches the engine to emergency mode if there is a malfunction in the EGR system.

Sometimes the EGR valve burns out under the influence of high temperatures, which is equivalent to it being stuck open. The causes of burnout may be incorrect operation valve control systems, high exhaust back pressure, faulty turbocharger bypass valve. Sometimes engine tuning to increase boost pressure leads to such consequences.

It should be noted that all the troubles described above are typical for vacuum-controlled pneumatic valves. Electric valves are much less susceptible to coking. Paradoxically, their service life is lower than that of pneumatic valves due to mechanical wear of moving parts. The increased gaps become clogged with soot, and the valve cannot be cleaned; only replacement is necessary.

However, not all problems associated with air EGR are due to the valve. Sometimes vacuum system parts or control elements are to blame. Therefore, you should not rush to dismantle the valve; first you need to check whether vacuum is supplied to it. On most vehicles, the vacuum controls not only the EGR valve, but also, for example, the turbocharger pressure control valve, intake manifold flaps, dampers air conditioning system, brake booster, etc. (it all depends on the specific model). Damage to any vacuum tube or valve sticking, air leaks in the intake manifold will affect EGR operation. Disturbances can be caused by a faulty control electrovalve that supplies vacuum to the pneumatic valve, and faulty sensor, part of the EGR control system.

The service life of various EGR systems ranges from 70 to 100 thousand kilometers (in domestic conditions about 50 thousand). After this, its components must be replaced. This is ideal. However, there are few willing to pay a lot of money. Simple and timely service system will help prolong her life. The EGR air valve must be periodically cleaned from carbon deposits on the seat and rod using carburetor cleaning fluid. This must be done carefully so that liquid that is aggressive to rubber does not damage it if it gets on the valve diaphragm. In systems with a control solenoid valve, it usually has a filter that protects the vacuum system from contamination. It needs to be cleaned.

When EGR starts to malfunction, many car owners prefer to turn it off. As a rule, this is done using a gasket cut from thin sheet metal and installed under the valve. Among experts, opinions on jamming the system differ. Some consider it completely harmless, and some even useful. The latter believe that as a result, the temperature in the combustion chamber increases, and this increases the risk of cracks in the cylinder head.

Simple mechanical damping of the valve and removal of the swirl flaps (where they exist) does not always lead to the desired results. On turbodiesels, there may be problems with regulating boost pressure and increased turbine wear. On modern engines The EGR valve must be “removed” and programmatically - by flashing the control unit. Otherwise, the controller will constantly generate an error or even put the engine into emergency mode.

The EGR system has been installed on cars since the mid-70s. It was at this time that manufacturers began to devote Special attention car environmental requirements.

The functioning of the EGR system is similar to the fact that a person inhales part of the exhaled air again. Air pollution is naturally reduced. But breathing also becomes difficult. Photo: auto-volgograd.com

Why do you need an EGR system?

The principle of operation of the USR system is based on a scheme where part of the output gases again enters the input manifold. This allows:

• reduce the level of nitrogen oxide in the exhaust;
• introduce an additional level of control over the toxicity of waste combustion products;
• reduce engine detonation;
• increase the completeness of fuel combustion;
• accelerate the heating of the input tract.

Modern engine control units internal combustion vigilantly monitor the performance of the USR, as one of the systems that ensures the environmental properties of the car. If the EGR is disabled or disabled by the user, the control unit can “choke” the engine for high speed, speeds and increased load. To eliminate this problem, chip specialists use a special software, reflashing the microprocessor of the control unit.

Design Features

The first USR system supplied to Chrysler in 1971 was not equipped with a valve. It worked constantly, even at low speeds and when starting the engine, which significantly worsened the engine parameters. Buick manufacturers were the first to include a pneumatic valve in the system, which controlled the timing of turning on the recirculation system based on the manifold vacuum pressure. This design turned out to be successful; pneumatic valves are still installed on some cars to this day.

This is what the main types of EGR valves look like. Photo: etlib.ru

The electromagnetic (also known as digital) valve, used on most modern cars, has significant benefits before pneumatic:

• the process of controlling the activation of the valve can be organized based on the readings of a large number of sensors (vehicle speed, crankshaft, throttle valve, differentiated pressure at the outlet/input of the USR, lambda probe, flow meter and others), increasing the accuracy of parameter control;
• the electric valve is more reliable than the pneumatic system;
• regulation of the gas bypass channel can be carried out smoothly in pulse or analogue mode;
• no air tube installation required.

The electro-pneumatic EGR valve system can be installed on engines that are regulated by two or more recirculation channels.

Structurally, gas outlet and valve parts are made of high-alloy steel, capable of withstanding high temperature loads of exhaust gases. If the piston group is worn out, the valve becomes contaminated with oil combustion products over time, begins to work incorrectly, and may fail.

Operating principle of the USR system

The main task of EGR is to reduce the percentage of nitrogen oxide in the exhaust gases. The formation of nitric oxide occurs when elevated temperatures combustion. The temperature can be reduced by reducing the oxygen concentration in the incoming mixture. By opening the recirculation channel, the USR valve lets in exhaust gases, in which there is practically no oxygen. The ignition temperature decreases, the concentration of toxic oxide decreases.

A decrease in temperature leads to a decrease in the efficiency of the internal combustion engine and its power. This is a tribute to environmental requirements.

In diesel engines, the amount of recirculated gases reaches 30–50%; the valve opens at idle and closes when the internal combustion engine warms up. IN petrol models The EGR valve closes under increased load. The amount of recirculating gases usually does not exceed 10 percent of the main composition.

Automatic shutdown of the EGR valve

Self-disabling EGR is performed in the following cases:

• severe wear of the internal combustion engine piston group in vehicles with high mileage to prevent combustion oil waste from entering the intake manifold, contaminating the spark plugs, and increasing smoke;
• chipping in the process of boosting the internal combustion engine;
• refueling with bad fuel, channel contamination;
• incorrect EGR algorithm.

In cars produced after 2010, blocking the USR system by the user leads to the fact that the control system begins to forcibly “strangle” the engine in order to reduce the concentration of toxic emissions. This is felt by the driver at increased speeds and load, high speeds. Experienced chipmakers, by forcibly disabling the USR system, reprogram the operating algorithm of the control unit and the fuel map.

Should I disable the EGR valve? You will find thoughts on this topic in the video:

Causes of EGR valve failure

The causes of the malfunction may be:

• poor quality fuel;
• injector malfunction;
• incorrect ignition angle adjustment;
• engine wear, low compression;
• excessive oil level;
• problems with electrical equipment;
• incorrect operation of internal combustion engine control devices;
• mechanical wear EGR valve.

Typically, problems with the EGR valve begin after 100,000 kilometers, when using low quality gasoline– after 30 – 40 thousand km.

Signs of malfunction

Main features incorrect operation USR systems:

• A clogged valve increases its response time and can lead to jamming, which in turn leads to increased fuel consumption.
• A constantly open valve reduces the engine's rated power and causes starting problems.

Valve failure is accompanied by the following symptoms:

• unstable idle speed;
• detonation when stopping the internal combustion engine;
• change dynamic characteristics auto;
• increased smoke;
• increased noise of a running engine.

Monitoring the serviceability of the EGR valve

In cars produced before 2005, a valve malfunction may not be manifested in any way, even by an indication signal light"CHECK ENGINE". Therefore, periodically (preferably before the start of the next operating season) it is recommended:

• visually check the integrity of the electrical wiring to the valve, tubes, fastenings, electrical connectors;
• measure the resistance of the solenoid valve winding (should be in the range from 15 to 200 Ohms);
• do computer diagnostics ICE.

Repair and replacement of the EGR valve

The exhaust gas recirculation valve is usually located in the easily accessible part of the engine compartment farthest from the bumper. Its dismantling and installation usually does not cause problems.

If the winding of the solenoid valve fails, it must be mandatory replacement. If the winding is intact, the problem is severe contamination of the channels, you can clean the USR valve. At a service station this procedure costs from 1000 rubles. You can save time and money by cleaning the EGR valve yourself.

The first stage of valve cleaning is immersing the recirculation and valve channels in a special flushing composition (time from 1 hour to 24 hours, depending on the degree of contamination). As such a composition, you can use a non-aggressive solvent, in as a last resort, acetone.

Most suitable option– carburetor cleaner. It is better to protect the electromagnetic part (winding) of the valve from contact with cleaning liquid: this can lead to its destruction.

The second stage consists of purging and further flushing the recirculation channels using a syringe or a medical enema. Solenoid valve it is better to open it by forcibly applying voltage to it with battery. The pneumatic valve can be opened by applying a vacuum of air to the pneumatic inlet.

When installing a new or repair valve, you should:

• use high temperature sealant;
• install only a new gasket;
• observe tightening thread forces;
• control the tightness of the tubes.

An option for replacing the EGR valve is presented here:

Bottom line

Some car owners do not pay enough attention to the performance of the USR system, considering it unimportant. However, when the EGR valve operates correctly, the engine runs smoother and wears less. Environmental characteristics are noticeably improving, this is so important in our time.

The EGR system (abbreviation for Exhaust Gas Recirculation) is an exhaust gas recirculation system. According to EGR technology, part of the exhaust gases again enters the air intake system to form a combustible mixture.

The system does not improve the performance parameters of internal combustion engines, rather the opposite. Installing EGR in cars is intended for:

• reducing the toxicity of exhaust gases, primarily the level of nitrogen oxide in the exhaust gases;
• introducing an additional degree of control over the vehicle’s environmental friendliness;
• reducing detonation processes;
• more complete combustion fuel;
• rapid heating of the inlet air tract.

In cars recent years release, EGR failure can block the correct operation of engines at high speeds and speeds. There is special software that reprograms the engine control unit.

EGR valve - what is it and why is it needed?

The temperature of the exhaust gases is very high, so for reliable operation it is made of durable high-alloy steel that can withstand temperature loads up to 2000 degrees Celsius. However, such steel does not have sufficient strength, especially when high temperatures. Therefore, the USR valve does not have a long service life.

Principle of operation

Reducing the concentration of nitrogen oxide in the exhaust gases of internal combustion engines is achieved by artificially reducing the oxygen content in the input mixture. This is achieved using the EGR valve, which bypasses part of the exhaust gases, in which almost all the oxygen has already been burned during the ignition process working mixture, into the inlet air tract.

Thus, the oxygen concentration in the inlet circuit decreases, combustion air-fuel mixture occurs at lower temperatures, toxic nitrogen oxide is formed with less intensity.

Of course, this reduces the efficiency of the engine and its power, but these are the strict requirements for environmentally friendly operation of the car.

If the USR valve does not work for some reason or is purposefully blocked, the engine control unit (especially those produced after 2010) gives a command to limit the supply of the fuel-air mixture, that is, it artificially “strangles” the engine.

Video about the EGR system:

Blocking the exhaust gas recirculation system is done in the following cases:

• excessive wear of the piston group, the presence of oil in the exhaust gases in order to prevent contamination of the spark plugs and ignition failures;
• boosting the engine, chipping;
• gas stations low-quality fuel leading to premature contamination of the valve;
• violation of the EGR system operation algorithm.

Classification of exhaust gas recirculation systems

IN modern cars Three types of implementation of the EGR algorithm are used:

Electronic

Installed on most cars after 2010. Control comes from the engine control unit through pulses supplied to stepper motor multistage device. Such a valve operates not only in the “open-closed” positions, but is capable of partially opening the recirculation path, which increases the accuracy of the system.

Pneumatic

The control is carried out by a vacuum valve, which controls the pressure in the intake system.

Electropneumatic

This system is used when control of several valves is required.

The control algorithm for the USR valve(s) can be organized based on the readings of the following sensors:

• exhaust gas pressure sensor;
• EGR sensor;
• gas temperature sensor;
• vehicle speed sensor;
• differential pressure sensor at the outlet and inlet of the EGR valve;
• flow meter;

It is not a fact that the readings of all of the above sensors will be involved in the process of controlling the USR valve. Each manufacturer independently develops an algorithm for the system. But in all cases it is quite complex.

In diesel engines, the EGR valve usually opens at idle speed. The amount of bypassed waste mixture can reach 40 – 50%. As the engine warms up, it closes.

In gasoline engines, the valve closes when the engine is idling and, vice versa, at increased load. The recycling rate is typically approximately 10%.

Causes of malfunction

The main causes of EGR system malfunction are:

• low-quality fuel, leading to the formation of excessive carbon deposits, can damage the valve after 10,000 - 20,000 km;
• problems with setting the ignition angle of an internal combustion engine;
• wear valve stem seals, decreased compression, other engine problems associated with the presence of oil in the exhaust gases;
• electrical equipment malfunction;
• violation of the signal processing algorithm by the engine control unit;
• increased oil level;
• wear of injectors;
• natural mechanical wear of the valve, usually occurring after 60 - 80 thousand km of car mileage.

Signs of a malfunctioning EGR valve

The main signs of malfunction and failure are as follows:

1. Valve clogged can lead to jamming during operation, as well as an increase in response time. Jamming contributes to a decrease in engine power, unstable idle speed, and “black smoke” in diesel engines. Untimely closing of the valve contributes to more “hard” operation, increased consumption fuel.
2. Constantly open valve The USR leads to a noticeable decrease in power and, as a result, a decrease in its throttle response.
3. Valve failure leads to a complex malfunction of the EGR system, which is usually indicated by the “CHECK ENGINE” indicator on dashboard and possible signs:

• unstable idle speed;
• increased smokiness;
• decrease / increase power;
• increased engine noise;
• detonation.

In cars with high mileage before the year 2000, the failure of such a valve may not manifest itself in any way, therefore periodically (preferably before the next autumn/winter and spring/summer seasons), as well as before undergoing technical inspection, it is recommended:

• produce visual inspection electrical wiring, connectors, tubes leading to the EGR valve;
• check (“ring”) the winding of the USR solenoid valve;
• Perform computer diagnostics of the engine control unit.

Video about signs of a faulty EGR valve:

Computer diagnostics of the engine control unit usually monitors the following parameters of the EGR system:

• recirculation ratio;
• duty cycle of PWM (pulse width modulation) pulses, if this type of USR valve control is used;
• valve on/off state with normal pulse control.

Replacing or cleaning the EGR valve

It is usually located on the left side engine compartment or on the partition of the engine compartment. It can be easily found by two hoses and an electrical connector connected to the valve (in the case of an electric valve).

Video - how to clean the EGR valve on a Honda Fit:

Its installation and dismantling during replacement or cleaning usually does not cause technical problems. In this case, the following requirements must be met:

• apply high-temperature sealant to the threaded connection of the thermal valve;
• use a new gasket when installing;
• To prevent leaks, observe tightening forces threaded connections(indicated in the repair instructions);
• check the tightness of the connection of the vacuum tubes and the correct connection.

Removing it (stub)

Many car owners (especially older cars) turn off the EGR system. This happens in cases where:

• The USR valve has failed and the car owner does not want to spend extra money on its purchase;
• the piston group is severely worn out, burnt oil enters the exhaust gases, strong carbon deposits are formed, which, if recirculated, heavily pollutes the working volume of the engine and spark plugs, and increases smoke;
• sometimes removing the USR valve temporarily restores the idle speed and throttle response of a “lost” engine.

For cars produced before 2000, when removing the USR valve, it is enough to disconnect its electrical connector. In some cases, then it is better to plug the tubes leading to the valve. This will not cause any malfunction in the vehicle's electrical equipment.

In the event that the control winding in the solenoid valve fails, you can turn on a regular relay or an incandescent light bulb in parallel with the valve to emulate it so that the engine error does not light up.

Video - is it worth turning off (silencing) EGR:

When the EGR system is turned off in cars manufactured after 2005, major problems associated with auto electrical may arise.

Basically, disabling the USR system is carried out in a process of improving the dynamic characteristics of the engine, called “chipping”. What is exhaust gas recirculation? This is similar to the fact that you will again release the exhaled air into your lungs. Yes, of course, the level of harmful exhaled substances will be lower, but breathing will also become more difficult and unpleasant. This is what many motorists think, and not without reason.

Video - how to properly turn off the EGR valve on a VAG:

There are many service stations that provide services software shutdown EGR. Then there is no need to make any mechanical or electrical changes to the engine control system. It is enough just to reflash the software of the control unit.

Video about EGR and particulate filter:

Some car enthusiasts who have it make attempts to independently reprogram it to remove EGR, using firmware and programs posted on the Internet. This is very risky, it is better to turn to professionals.