How does an EGR valve work? | How to Clean EGR Valve?

EGR stands for Exhaust Gas Recirculation. The main function of the EGR valve is to control the emissions of exhaust gases in both petrol engines and diesel engines. It plays a big role in maintaining the health of the vehicle’s engine and exhaust system. The exhaust gas recirculation valve precisely recirculates heavy exhaust gases into the engine’s intake system to improve engine efficiency, reduce NOx emission rate and lower fuel consumption. This article mainly explains the working, types, and many other aspects of the EGR valve.

What is an EGR valve?

The EGR valve is a part of the engine which uses to control the emission of exhaust gases (such as NOx) into the environment. It allows a controlled amount of exhaust gas to flow into the intake manifold. Hence, the exhaust gas recirculation valve opens and closes according to the requirements.

In the latest IC engines, EGR (Exhaust Gas Recirculation) system controls the emission of NOx produced during the combustion process of the fuel (such as petrol, diesel, or gas).

Exhaust Gas Recirculation valve

In the fuel combustion process, the engine sucks air from the atmosphere and mixes it with the fuel. As the air and fuel mixture starts burning into the combustion chamber, the temperature of the mixture increases, which causes the emission of nitrogen oxides (NOx).

If your car does not have EGR valves, the produced NOx may be exhausted into the atmosphere, which can produce some serious health problems such as cancer, passenger death, etc.

The working principle of the EGR system consists in returning a small part of the exhaust gases via the intake manifold into the combustion chamber of the engine. This combustion chamber lowers the combustion temperature and reduces the NOx emission rate.

This valve is a most vital part of the engine and is normally shut-off. It drives by a built-in stepper or vacuum motor. It connects the intake manifold to the exhaust manifold. In this way, the EGR valve controls the flow of recirculated exhaust gases according to the engine requirement.

Working of EGR Valve

The atmospheric air has almost 80% nitrogen. When this nitrogen is heated at an extremely high temperature inside the combustion chamber of the engine, it reacts with the normal inert gas and generates dangerous NOx. This produced NOx transfers into the EGR (exhaust gas recirculation) system from where it discharges into the environment.

EGR Valve working

Exhaust Gas Recirculation system sends an additional part of the NOx back into the combustion chamber, where it is combined with fresh air and reduces the chamber’s temperature.

This system reduces the amount of O2 and rises the water vapor content in the combustion mixture, which decreases the maximum temperature of the combustion process. This is because the NOx production process increases as the maximum combustion temperature increases.

The EGR system has a valve. This valve controls the emission rate of NOx. It installs between the exhaust manifold and intake manifold. In simple words, this valve makes a connection between the intake manifold and exhaust manifold.

The EGR valve begins to operate as soon as the engine starts, attains the appropriate working temperature, and increases the vehicle speed. It decreases the NOx emission rate.

As soon as the vehicle speed reduces and the engine stops, the valve returns to its closed position and stops the exhaust gases flow.

Read Also: Different types of Engines

Types of EGR Valves

EGR valve has the following major types:

  1. Diesel high-pressure EGR valve
  2. Digital EGR valves 
  3. Diesel Low-pressure EGR valves
  4. Vacuum operated EGR valves
  5. Gasoline EGR valves

1) Diesel high-pressure EGR valve

This valve installs just before the diesel particulate filter. It redirects the high-soot, high-flow exhaust gases before entering the diesel particulate filter. If the soot or ash combines with oil vapors, it can produce sludge.

The diesel high-pressure EGR valve returns the exhaust gases to the intake manifold through a tube or inner hole in the cylinder head. There is another valve which uses to produce vacuum in the intake manifold that is inherently absent in diesel engines.

2) Diesel Low-pressure EGR valves

These valves install after the diesel particulate filters. It diverts the exhaust gases after they have passed by the diesel particulate filters. The flow rate of these exhaust gases is slow, but there is almost no soot. These gases then return to the intake manifold through the pipe.

Read Also: Different types of Valves

3) Gasoline EGR valves

It also diverts the exhaust gas as a high-pressure diesel valve. This valve is most commonly used in gasoline or petrol engines. As the engine piston moves up and down, a vacuum produces inside the compression chamber sucks in the exhaust gases and the EGR valve controls the gas flow.

Read Also: Working of Petrol Engine

4) Vacuum operated EGR valves

This valve uses a vacuum solenoid to change the vacuum pressure on the diaphragm. The motion of the diaphragm controls the opening and closing position of the valve. Some types of valves also have a feedback sensor to notify the ECU system about the valve position.

5) Digital EGR valves

It has a stepper or solenoid motor and a feedback sensor as well. This valve receives pulse width modulation signals from the ECU to control the flow of exhaust gases.

Symptoms of Bad EGR Valve

The EGR is a most vital part of the car engine. It helps to control the flow and emission of exhaust gases. In case of exhaust gas recirculation valve failure, you may face many problems related to the vehicle engine and your health.

There are different symptoms of a bad EGR valve through that you can easily identify your vehicle’s bad EGR valves and repair them on time. Following are some most common signs of a bad EGR valve:

1) Poor Engine Performance

If the performance of your car engine has been reduced, it may cause due to a bad EGR valve. As you observe a reduction in the performance of your car engine, immediately check your EGR. If you can’t check, contact a technician and repair it.

poor engine performance

2) Engine Warning Light

When you drive your vehicle, you should always monitor the engine indicator, which informs you about the health of your engine valve. If, under any circumstances, the EGR valve fails, the engine indicator will most likely illuminate on the dashboard (unless it is damaged in some way, it will need to be replaced as well).

engine warning light due to bad egr valve

The engine indicator only turns on when the ECU system of your vehicle detects a problem with the engine or other parts directly connected to it.

3) Smell of Unburnt Fuel

If your EGR valve doesn’t work properly, the engine consumes more fuel than usual because it works harder to move the vehicle. In such a case, the peak combustion chamber temperature will be very high, and it will emit more NOx. This increases the smell of fuel, and if the car air conditioner is not in the recirculation phase, you can feel it in your car.

smell of unburnt fuel

4) Failed Emissions Test

When the increase in emissions needs to be tested every 6 months, there are very high chances that your EGR valve has been damaged or failed.

However, this test can’t let you know the exact health of your EGR, but if the emission test fails then you must immediately contact a professional for the proper inspection of your valve.

Failed Emissions Test

5) Rough Idling

If your engine’s EGR valve fails, it may produce rough idling. The rough idling is a most common symptom of a failed or damaged EGR valve. In such a situation, the valve remains stuck in the close or open condition. This can also represent that too much exhaust gas is going into the combustion chamber.

Rough Idling due to bad egr valve

6) High Vibration

Sometimes, a vehicle produces high vibration due to a bad EGR valve.

7) Engine Knocking

If your engine is producing knocking extensively, it may be due to a bad EGR valve. This is because, the purpose of the EGR is to maintain the lower temperature of the engine and prevents it from overheating. As the EGR fails, the engine overheats and it produces knocking.

Read Also: Different types of IC Engines

How to Clean an EGR Valve

If you want to clean your EGR system, follow the below-given steps to clean an EGR valve:

  • First of all, put the car on a flat and leveled surface as well as the car must be in a “park” position. Turn on all brakes of your car.
  • Turn off the engine of the car. Disconnect the cable from the negative terminal of the battery.
  • Check whether you have an electrically or mechanically controlled EGR valve. This is most commonly mentioned in the EGR valve repair or manufacturer manual.
  • Eliminate the bolts of the valve and all other blocking parts to the valve.
  • During the elimination process of the EGR valve, ensure that it must come out with a gasket. If you observe bad gasket symptoms on your gasket, replace it with the new one.
  • Remove all electrical connections that are connected to the valve.
  • Wear Personal Protective Equipment (PPE) such as safety glasses and gloves for your safety.
  • After wearing PPEs, start the cleaning process.
  • Spray EGR valve cleaner inside the valve. Keep spraying until the carbon layer fully removes from the valve and only the cleaning fluid starts coming out.
  • Use a blunt scraper and a pipe cleaning brush to eliminate carbon collection.
  • Repeat this process until the full removal of the carbon deposits.
  • Use a clean cloth to wipe the valve surface.
  • If you have difficulty in cleaning the valve with a pipe cleaning brush, soak the valve in the cleaning solution for some time.
  • Repeat the brushing process again after soaking.
  • Reinstall the valve with a new gasket. Unscrew the screws and reconnect the electrical parts, and vacuum.
  • Reconnect the negative terminal of the battery. Turn on the engine and make sure the engine lights are off.

EGR Valve Replacement Cost

The average replacement costs of the EGR valve vary according to the region where you live and the type of brand.

The average replacement cost of the EGR valve is from $220 to $370.

The replacement cost of the valve parts varies from $170 to $280. If you are not replacing it yourself and hiring labor, the labor cost varies from $55 to $90.

The below given tells the replacement cost of the EGR valve:

Average Cost$220 – $370
Valve Parts Replacement Cost$170 – $280
Labor Cost$55 – $90

How do you know it is time to clean EGR Valve?

Following are some signs that tell you that your valve needs cleaning or replacement:

  • Reduction in the engine efficiency
  • Reduction in gas mileage
  • The smell of unburned gas fumes
  • Engine ‘ping’ when under load
  • Engine overheating
  • Poor engine performance during the drive
  • Engine vibration
  • Rough idle
  • Problems in starting the engine

Best EGR Valve Cleaners

  1. Wynn’s WY23381 Diesel EGR Cleaner
  2. Sea Foam SS14 Cleaner and Lube
  3. Liqui Moly 2033 Pro-Line Intake System Purge
  4. OXICAT – Oxygen Sensor & Catalytic Converter Cleaner
  5. Holts EGR & Carb Cleaner
  6. Fastcar Wynn’s Diesel Turbo Cleaner

FAQ Section

What are the signs of a Bad EGR Valve?

The most common signs of the bad EGR (Exhaust Gas Recirculation) valves are given below:

  • Check Engine Light on
  • Rough idling
  • Failed smog test
  • Fuel smell
  • An increase in the fuel consumption
  • Reduction in the engine performance 
  • knocking, tapping, or pinging sounds

Can you drive with a Bad EGR Valve?

Yes, even if the EGR valve fully fails, you can still drive your car. But your car will not run properly. You may observe some symptoms of bad EGR such as unstable idling, engine check light, unburned fuel smell from exhaust, poor performance of the engine, and emissions check failures.

Can EGR Valve be Cleaned?

Yes, maximum problems of the EGR system may be resolved by careful cleaning the valve with a throttle body cleaner. After proper cleaning, you won’t need to change your valve.   

What does EGR Valve do?

EGR valves of the engine help to reduce exhaust gas emissions. If the engine overheats and the level of the O2 in the combustion chamber increases then the NOx (hazardous gas) emission rate also increases.

In such conditions, the EGR valve returns some of the exhaust gases into the chamber to replace some O2 and reduce the engine temperature. This decreases the emission rate of the NOx gas.

When was the EGR system invented?

In 1970, the EGR system was first time introduced on vehicles. 

What is the EGR valve cost in UK?

The cost of the new EGR valve depends on the car model and the brand type. The average cost of a new EGR in UK is from £80 to £370. If you are not installing it yourself and hire labour, the labour may also charge you from £60 to £150.

What are the types of EGR Valves?

The exhaust gas recirculation or EGR valve has the following major types:

  1. Gasoline exhaust valve
  2. Diesel high-pressure EGR valve
  3. Vacuum operated EGR valve
  4. Digital EGR valve 
  5. Diesel Low-pressure valve
Read Also
  1. Different types of Engines
  2. Working and types of Diesel Engine
  3. Types of Reciprocating Engines
  4. Working of Stirling Engine
  5. Working of Fuel Pump
  6. Working of Carnot Engine

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