How Does an EGR Valve Work (Symptoms of a Bad EGR Valve)

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Are you wondering how does an EGR valve work and maybe you trying to find out what are the symptoms of a bad EGR valve? This article covers all that you need to know about EGR valves.

The EGR valve is very important when regulating exhaust emissions and it can cause great damages when it is not working properly. The EGR stands for Exhaust gas recirculation system which is a system that was designed to take back exhaust gas into the vehicle. It is mostly done to reduce NOx emissions and cylinder temperatures. It is responsible for controlling the flow of exhaust gases.

Here are what we will discuss in this article:

How Does an EGR Valve Work (Symptoms of a Bad EGR Valve)

What is the role of the EGR valve?

Like you may know the EGR is present to your car to reduce emissions which is accomplish by rerouting exhaust gasses that comes from car engine back to the combustion chambers. This action helps reduce the temperature within combustion chambers thereby mitigating any problem and impact to the engine which can lead to environmental damage of the surrounding.

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Types of EGR valve

There are numerous types of EGR valve  but the foremost types of EVR can be are as follows:

  • Diesel high-pressure EGR valves -These first diverts the high soot and flow of exhaust gas before it has the chance to get into the diesel filter.
  • Diesel Low-pressure EGR valves -These ones avert exhaust gas after it has gone past the diesel particulate filter but for this EGR valve, the gas it lets in has a lower flow and is almost clean free of soot. Later the gas will now be passed back with a pipe through inlet manifold.
  • Gasoline EGR valves -These EGR valves divert the exhaust gases, similar to a high-pressure diesel equivalent. Here the exhaust gases are drawn in and the flow is been regulated with the opening and closing of the EGR valve which is possible due to the vacuum created by cylinder depression.
  • Vacuum operated EGR valves – These makes use of a vacuum solenoid to vary the vacuum to the diaphragm that is during an, in turn, open and closing of the  EGR. Some of the valves here comprise a feedback sensor that informs the ECU (that is the engine control unit) of the position of the valves.
  • Digital EGR valvesThese features a solenoid or stepper motor and a feedback sensor. The Digital EGR valves receive a pulse width modulated signal from the ECU, to regulate exhaust gas flow.

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What damage can a faulty EGR valve cause?

When the EGR is faulty, the engine of the car starts overheating. This will lead to a breakdown of the engine oil that is feeding the turbocharger. The bearings in the turbocharger will start failing because of the problem with the engine oil. Replacing the turbocharger can be very costly.  However, if you repair it without solving the EGR problem, it will only repeat itself.

Lubricating Oil will start leaking into the combusting chamber, as a result of engine overheating. The engine will now start running on oil instead of fuel. The driver might not be able to stop the engine again once it has gotten to this. The engine will then exhaust the oil and end up breaking down.

 Can a bad EGR valve cause overheating

If you have been asking yourself this question, then the answer is YES. In fact, it is one of the first symptoms of a faulty EGR. Because the EGR will restrict the flow of gas through the cooler, the engine will experience a large amount of heat which leads to overheating. The restriction of heat through the cooler is caused by carbon built up in it. This will no longer let it cool exhaust gases and so it leads to overheating.

What problems does a bad EGR valve cause

Failed EGR can cause problems with other parts of the system such as spark plug, fuel litters, engine sensor, fuel pump regulator or spark plug wires. It will also affect the air-fuel ratio of the vehicle. Problems will arise in the power and acceleration of the vehicle. The fuel will no longer be efficient and the emissions of your car will increase.

Symptoms of a bad EGR valve

A damaged EVR can cause different damages and problems with the slow and operation of the EGR system and it will affect performance.  Some of the symptoms that you might notice are:

  1. The check engine light is on. When there is an issue with the car’s EGR, the check light will come on to notify the driver of the problem.
  2. The rough Idle is a very common symptom of a faulty EGR valve. The exhaust gas recirculation leads to rough idling if it isn’t functioning properly.
  3. A faulty EGR valve will lead to poor engine performance. It can affect the car’s air-fuel ratio and also reduce power and fuel efficiency. The car might also have a problem while accelerating.
  4. When the car is accelerating, it may make a knocking or pinging sound. The faulty valve isn’t allowing the right amount of exhaust to dilute the mixture of air-fuel. A continuation of this might lead to failure in other components.
  5. Your car will start performing poorly and slowly.
  6. The consumption of fuel will increase if there is a damaged EGR valve.
  7. If the exhaust gas is leaking, you will always smell fuel.

When you notice any of these symptoms, it is important to take your vehicle to professionals in order to avoid more damage.

Can I drive with a bad EGR valve

When you drive with a faulty EGR, you increase the probability of damaging your car’s engine. EGR valve uses exhaust gas to cool the combustion chamber which makes it cooler because it does not consume much oxygen. When your EGR valve is faulty, the emission will increase which might cause overheating. Once the engine is overheating, it is only a matter of time before it destroys the engine. The piston might seize or expand because of high temperature. It might also destroy some other components like valves and crankshaft. It is not advisable to drive with a faulty EGR, be patient and let it be fixed.

How does an EGR valve work

The Exhaust Gas Recirculation is an emission control system that reduces the amount of NOx (Nitrogen oxide) in the vehicle’s exhaust gases. The exhaust gas is made up of emissions such as hydrocarbons, carbon monoxide, particulate matter, and nitrogen oxides. Its main function is reducing emissions.

How does it do that? It is very simple as the EGR reroutes the gases from the engine back into the engine combustion chambers. It also has two main settings that are open and close. When the engine is starting up, it is closed but during idle and with low speed, the EGR will start opening gradually. During acceleration, it will close to enable a huge amount of oxygen to enter the cylinder.

There are two types of EGR which are the vacuum, and electronically operated valves. Old cars usually use the former. They use a vacuum to open and close the valve. Modern cars, on the other hand, use electronically controlled EGR which is mostly controlled using the ECM (Engine’s Control Module) of the vehicle.


That is all there is to know about the EGR valve. Do not forget to take your vehicle to professionals if you are having any of the symptoms mentioned above. You risk damaging the engine if you keep managing with the condition.

I hope this post on how does an EGR valve work and then symptoms of a bad EGR valve has helped you?

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