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What is an EGR Valve in a Car? Facts and Figures.

What is an EGR Valve in a Car? Facts and Figures.

The Engine Gas Recirculation valve, or EGR valve, recirculates quantities of exhaust gas to the engine intake system for optimum engine efficiency. Without it, engines do not perform properly. If undiagnosed, it could lead to further engine issues and expensive repair costs.

Auto Repairs Are EXPENSIVE


Inefficient engines cause a lot of headaches for car owners. At best, the car doesn’t run as well as it could. You could also end up with a vehicle that breaks down on the shoulder of the expressway or dealing with costly repair bills. If the ERG valve is to blame, you should learn more about what it does.

This blog outlines what an EGR valve is, what it does, why it fails, and how to replace it when it fails. The approximate repair estimate is given for the cost in 2021, however, this varies depending on the mechanic, location, availability of parts, and any accompanying underlying issues requiring replacement.

What is an EGR Valve?

The EGR valve plays an important role in reducing nitrogen oxide emissions within the engine’s systems.

There are many components of an engine and one of the most important is the EGR or Exhaust Gas Regulation system.

The Exhaust Gas Regulation System is a method to control nitrogen oxide emissions produced during the combustion process. The EGR system works by returning a portion of exhaust gas to the engine’s combustion chambers, lowing temperatures, and reducing the amount of nitrogen oxide emitted.

The EGR valve is the main component of the EGR system. It connects the exhaust manifold to the intake manifold and is controlled by a vacuum or electric motor. The function of the EGR valve is to control the flow of exhaust gas being recirculated; the valve is normally closed.

Nitrogen oxide is a major component of smog and can have detrimental effects on both human life and the ecosystem. Lowering these harmful emissions helps save the environment and has a positive impact on human health. That’s always a positive!

How does an EGR Valve Work?

Modern vehicles incorporate EGR valves to reduce nitrogen oxide emissions and meet strict regulations. The EGR system recycles a small amount of the exhaust gas back into the combustion chamber where it combines with fresh air.

This lowers the amount of oxygen and increases water vapor which reduces combustion temperature. When combustion temperatures are higher, more nitrogen oxide is created. The EGR valve reduces the amount of nitrogen oxide produced by the engine.

The EGR valve works once the engine has started, is operating at the correct temperature, and the vehicle’s speed increases. Gradually, the EGR valve regulates the exhaust gas flow.

Once the engine slows down and the engine stops, the EGR valve returns to its closed position and prevents the flow of exhaust gases.

Various Types of EGR Valves

There are several types of EGR valves including the older vacuum-operated valves and newer electronically controlled valves. They can be summarized as follows:

  • Diesel high-pressure EGR valves
  • Diesel low-pressure EGR valves
  • Gasoline EGR valves
  • Vacuum-operated EGR valves
  • Digital EGR valves

Diesel high-pressure EGR valves divert exhaust gas before it enters the filter as the soot exhaust can combine with oil vapor to create a nasty sludge. The gas then passes back to the intake manifold through a pipe or drillings in the cylinder head.

Diesel low-pressure EGR valves divert exhaust gas after it has passed through the filter as it is almost completely clean of soot. Then, the gas passes back to the intake manifold.

Gasoline EGR valves function similarly to the high-pressure diesel equivalent. The vacuum created draws the exhaust gases in and flow is regulated by the opening and closing of the EGR valve.

Vacuum-operated EGR valves use a vacuum solenoid to vary the vacuum and in turn, open and close the EGR.

The digital EGR valve also has a solenoid, or sometimes a step motor, and a feedback sensor. These valves receive a pulse signal from the engine control unit to regulate efficient exhaust gas flow.

EGR Valve Systems throughout time

Modern vehicle engines use a variety of EGR valve configurations. Understanding what kind of EGR system your vehicle has in case you have problems.

In older vehicles, EGR valves were bigger and occupied more space. They were normally 3 inches in diameter and were placed on the upper side of the engine. There was a vacuum hose that ran the EGR valve. Nowadays, however, this design has taken a new shape.

In semi-modern vehicles, manufacturers used an electronic vacuum EGR valve. This valve helped the EGR position sensor communicate faster and more efficiently with the engine control unit.

In newer models, the EGR system is similar to semi-modern vehicles except the vacuum control has been replaced by a digital valve. Digitalization can make the car more efficient but also presents a drawback: there’s another way this part can have a problem (sensor/software issues).

Additionally, some models have replaced the EGR valves with EGR jets, although it is rare. 

Fun fact: Some high-efficient engines don’t have an EGR at all.

Why do EGR Valves Fail?

EGR valves operate in an aggressive environment and over time experience wear and tear. 

The single biggest cause of failure is carbon buildup from exhaust gases. Over time, this clogs tubes, exhaust gas channels, and eventually the valve’s plunger mechanism causing it to stick open or stick closed.

Symptoms of a Faulty or Failing EGR Valve

EGR valves can cause a lot of problems. You may experience one or more of the following if your EGR valve is faulty:

  • Poor engine performance
  • The engine warning light is lit
  • Fuel smell
  • Failed emissions test
  • Rough idling

More than likely, the first and most frustrating symptom of a faulty EGR valve relates to engine performance. If you drive with a faulty EGR valve, you will experience difficulty accelerating and an overall power reduction.

Although the engine indicator light could be lit for a variety of reasons, one of them could be a faulty EGR valve. 

If the EGR valve isn’t functioning properly, the engine is using more fuel than necessary leaving more hydrocarbons in the tailpipe. This all leads to an increase in fuel odor. Not only is this terrible for your health, but also a definite sign that something is wrong with the engine.

Some vehicles need to be tested for emission levels every so often and if you find yourself in that situation with an increased emission level, there is a high probability you have a faulty EGR valve.

When the EGR valve is faulty, it remains in either an open or closed position until the problem is fixed. This will cause rough idling. 

Not only is this bad for the vehicle, but it could also cause the automobile to fall out of compliance with local and state emissions regulations. This means that the governing bodies won’t approve your car for road use until you complete the repair!

Troubleshooting a Failing EGR Valve

Determining the exact problem with the EGR valve is difficult and should be left to a mechanic; however, there are a few steps to follow that can help make a diagnosis:

  • Read any fault codes on an electronically controlled EGR valve using a diagnostic tool. You can do this by visiting a mechanic or asking for assistance at a local auto parts store. Many locations will do this for free.
  • Check that vacuum lines and electrical connections are connected properly.
  • Use a vacuum gauge to check the vacuum supply is accurately functioning between 2,000 and 2,500 rpm. If you don’t have this tool, ask a mechanic for assistance.
  • Check the vacuum solenoid while the engine is running. If the solenoid does not open when the engine is running, is stuck in an open or closed position, or has a bad electrical connection, the EGR will be affected.
  • Remove the EGR valve and check for carbon build-up and clean if necessary.
  • Inspect the EGR passageway for clogging and clean if necessary.

Types of Bad EGR Valves

There are three types of bad EGR valves and each shows different symptoms: the piece can either stay closed all the time or stay open all the time. Sometimes, it remains clogged because of unburned carbon deposits.

When the EGR valve stays open all the time, it more than likely means there is a vacuum leak present in the system. The leak results in incomplete combustion and typically means rough idling. That isn’t great for the vehicle.

When the EGR valve stays closed all the time, it means there are a large amount of nitrogen oxide emissions building up with no place to go. This results in engine knocking and possible disruption in engine timing. Engine knocking is a sign that it’s time to take the car to the shop as soon as possible.

When the EGR valve is clogged, unburned carbon deposits stay in a certain position. Similar to the EGR valve remaining open constantly, this results in rough idling. 

Replacing a faulty EGR valve

Replacing the EGR valve is a difficult process. If you are a novice DIYer, this job is best left to a mechanic or car professional. 

However, if you insist on trying to replace the valve, you can do so by following these steps:

  • Remove the engine cover.
  • Loosen the electrical cable on the valve. Remove the electrical connections and/or vacuum lines and fastening screws.
  • Clean the EGR valve mounting surface and fit the new EGR valve and gasket. Remove any carbon build-up you see.
  • Line up the EGR valve with the bolt holes and gasket. Tighten all fasteners.
  • Reconnect the vacuum lines and/or electrical connections.
  • Use a diagnostic tool to reset the engine warning light and check for any errors.

The average cost for EGR valve replacement is approximately $360, with the majority of this cost going towards parts. This estimate varies depending on vehicle model and location.

In general, we recommended using a licensed or certified mechanic for the repair. Although it’s tempting to make this repair a Saturday afternoon DIY project, you really shouldn’t unless you have the necessary time, tools, space, and knowhow. 

Because the EGR valve relates to both the engine health and exhaust system, if left as an ongoing problem, it could cause more problems such as engine failure. If your car is old or no longer worth any type of investment, it may be better to send it to a junkyard.

EGR System: Important for the Engine Performance

The EGR system is one of the most important components of the engine. 

If your vehicle is demonstrating the symptoms of a bad EGR valve, it is worth having a mechanic make a diagnosis. This is not a problem to avoid with your vehicle, as it could lead to more problems.

Unfortunately, being a car owner means both paying for maintenance and repairs. Sometimes, the best option is to get rid of the car and send it to a junkyard, especially if that investment could be better used towards a new vehicle.

Most of the problems we discuss in a recommendation to send the car to the junkyard due to the high cost of repairs that aren’t justified in an older and already failing vehicle. This repair, on the other hand, is often quick and not that expensive (in comparison to engine rebuilds, broken transmissions, etc.).

If your car, however, has a whole slew of problems, is older than 12 years old, and is pushing 150,000 to 200,000 miles, then this little repair could still be the sign that it’s time to send the automobile to the junkyard.

Understanding the way your vehicle’s EGR system works can help you make the right decision.