9 Symptoms of a Failing EGR Valve

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Most people don’t know what the EGR system does or how it works. 

But, the EGR valve can play a crucial role in your cars engine performance and it’s ability to pass emissions tests. 

Identifying the symptoms of a bad EGR valve is challenging if you don’t know what you’re looking for. 

Don’t worry you don’t need  a mechanic just yet. In this post, I will guide you on 9 key symptoms that will help you determine if you have a failing EGR valve. 

1. Reduced Fuel Economy

One side effect of a failing EGR valve is reduced fuel economy. If the EGR is not functioning correctly, the fuel inside your engine won’t reach optimal temperatures.

This is because the EGR valve can’t inject additional fuel to increase the temperature of the gas to improve fuel efficiency.

An easy way to determine if you are experiencing reduced gas mileage is refilling your tank more frequently.

This is especially easy to measure if you follow the same commute every day.

Let’s say you refill your tank every Monday. If all of a sudden you need to refill on Saturday, then this might be a sign of reduced gas mileage.

In newer vehicles, the gas mileage is displayed on your dashboard or the central display. Keep track of this value over several weeks.

You can compare your MPG to the MPG recommended for your car’s specific year and model.

An easy way to determine your vehicle’s average gas mileage is using the U.S Department of Energy’s fuel economy website.

If your car does not display the MPG on the dashboard, you can use an app to track your MPG.

If your car has a lower MPG than the recommended MPG for your vehicle, I suggest you inspect your spar plugs.

2.Rough Ideling


Rough idling is characterized by jerking or stutters when driving or starting the vehicle. This is especially common if you are driving with a heavy load.

When you see your Check Engine Light cut on, feel a rough idle, a stalling, and a hissing sound from the engine bay – these are all symptoms of a vacuum leak.

You will feel your engine running at a higher RPM or having difficulty maintaining stable RPMs on idle.

The RPM while idling decreases below the ideal level, which results in rough idle when there is an uneven supply of fuel. You will need to restart the vehicle if the RPM falls too low because it will stall.

3. Stalling when Idle

Another common sign that your EGR valve is faulty is if your car begins stalling while it’s idle. 

While your car is idle your engine needs an even supply of fuel.

With a faulty EGR your fuel might be to rich or not rich enough. 

The results, is that your engine won’t reach optimal temperatures and this can cause your engine to stall. 

4.Smell of Fuel

When the EGR valve is not operating properly, your car will have a strong gasoline smell.

The strong smell of fuel is typically due to increase fuel that your engine uses when the EGR valve is faulty.

Since the EGR won’t be able to inject additional fuel into the engine, your engine will naturally consume more gas.

If you begin to smell a strong fuel smell, this is a sign that your EGR valve is fault. This smell is typically associated with older cars. This smell can also happen in newers cars with a fault EGR vale.

5. Failed emission test

The EGR valve plays a crucial role in a car’s ability to reduce emissions and improve engine performance.

When your EGR valve is faulty, your car will emit much higher levels of Nitrogen Oxide (NOx). This is a huge concern for new and old cars alike.

First, the higher levels of emissions are damaging to the environment.

Second, these higher emissions typically won’t pass the emissions test required by governing bodies.

In the U.S, each state requires emissions tests. The frequency varies for each state. For example, California requires emissions test every two years.

Other states, such as the U.K, requires emissions tests every three years.

If your car fails the emissions test, one of the first areas you can inspect is your EGR valve.

6.Check engine light remains on

Another sign that your EGR valve is faulty is if your check engine light remains on. 

If your check engine light is on and you don’t have any other engine issues, this is a sign that your EGR valve is faulty. 

One of the easiest ways to determine why your check engine light is on, you can use an OBD2 scanner. 

Use the scanner to help narrow down why your check engine light is on. 

The error codes for a faulty EGR valve are: 

  • P0400: Exhaust Gas Recirculation Flow
  • P0401: Exhaust Gas Recirculation Flow Insufficient Detected
  • P0402: Exhaust Gas Recirculation Flow Excessive Detected
  • P0403: Exhaust Gas Recirculation Control Circuit
  • P0404: Exhaust Gas Recirculation Control Circuit Range/Performance
  • P0405: Exhaust Gas Recirculation Sensor ‘A’ Circuit Low
  • P0406: Exhaust Gas Recirculation Sensor ‘A’ Circuit High
  • P0407:Exhaust Gas Recirculation Sensor ‘B’ Circuit Low
  • P0408: Exhaust Gas Recirculation Sensor ‘B’ Circuit High
  • P0409: Exhaust Gas Recirculation Sensor ‘A’ Circuit

If you receive any of these codes, this is a sign that your EGR valve is damaged. 

7. Low engine power

One of the most common problems you might encounter would be acceleration and power. It happens in both open or closed valves.

Although it might also mean you have a bad fuel filter, so you’d first have to make sure that your EGR valve is the issue.

8. Random Misfires and Shaking

When idle, the valve should stay closed. However, if carbon deposits are too much, this might cause them to stay open.

The intake air won’t have enough oxygen for combustion, which would result in this issue.

9. Knocking sound

The heat inside the chamber will rise faster. This may lead to fuel igniting too early while your engine is still at a low RPM, hence the knocking sound.

What is the EGR valve?

The EGR valve stands for exhaust gas-recirculation valve. The main function of the EGR valve is to maintain the cars exhaust system and engine health. 

The EGR valve uses an intake vacuum to control the engine’s air/fuel mixture. The release of fuel will control the temperature inside the engine.

The reduction in temperature improves Nitrogen Oxide (NOx), increases fuel efficiency, and improves engine performance. 

Where is the EGR valve located?

egr location

The EGR is typically located on the side or on top of the intake manifold.

The intake manifold is typically easy to find. In most cases, the EGR valve is located high up in the engine bay.

In most engines its on one side of the cylinder head. In other engine such as V-engines the EGR valve is located between the cylinder heads.

What causes the EGR valve to fail?

One of the most common reasons that EGR valves fails is because a build up of deposits and gunk. 

These deposits can cause the EGR valve to either get stuck open or stuck closed. In either case, the EGR valve won’t operate properly if its stuck open or closed. 

Other common reasons that the EGR might malfunction and cause a weak flow include: 

  • Clogged passageway 
  • Faulty differential pressure feedback sensor (DPFE) 
  • Clogged catalytic converter 
  • Clogged Diesel particulate filter (DPF) 
  • Faulty EGR temperature sensor 
  • Short circuit of the electrical problems 

An EGR system with an excessive flow can be caused by: 

  • Clogged passageway 
  • Leaks in the air intake system 
  • Problems with turbocharger 
  • EGR Control Back Pressure Transducer valve 
  • Damaged or missing gasket 
  • Issues with EGR vacuum control or switching valve 
  • Short circuit of EGR valve 
  • Carbon buildup 
  • Defective EGR solenoid

How Much Does It Cost To Replace an EGR Valve?

The replacement cost of EGR valve depends on the type of car and the quality of the EGR. 

The average cost of the EGR is between $150 and $350. Labor cost will typically cost between $100 and $300 depending on how difficult it is to access the EGR system and EGR valve. 

The total cost can vary from $250 to $650. 

One way to save money is to purchase a low budget EGR. While these are inexpensive they typically don’t operate as well as other EGR valves. Also, you can opt to install the EGR yourself to save money on labor costs. 

Most EGR valves are located near the top of the engine bay then the replacement can be relatively easy to replace. 

What happens if you ignore a faulty EGR valve?

Driving on a faulty EGR valve won’t cause serious damage to your car. 

Overtime, driving with a faulty EGR valve can lead to many performance problems. 

Overtime your car will experience reduced acceleration, loss in power, and decreased fuel efficiency. 

Overtime, your EGR system can begin to fail and cause other engine issues. 

One of the main concerns when an EGR begins to fail is the increase in emissions and possibility of failing government required emissions test. Without a passing score on these tests you won’t be able to drive your car. 

What happens when the EGR Valve is stuck Open?

EGR valves that are stuck open experience vacuum leak. 

When this happens your engine is being overwhelmed with too much gas and not enough oxygen. This means that the combustion process would take longer than usual. 

A noticeable effect of this is when your engine tends to stall or has a rough idle. You should also watch out for those P1404 and P1406 error codes on your engine light.

Now, how do we diagnose this issue on your vehicle?

Well, one thing you can do is to look at the plunger shaft to see whether it’s open or not. Once you see the error codes, you should remove the plug and fill it with carbon cleaner.

If it leaks when the lid is upside down, that means it’s stuck open. You can use a valve cleaning kit and pull a vacuum on the valve.

What happens when the EGR Valve is stuck Closed?

When your EGR valve is stuck closed you will notice that your car beings releasing more emissions that usual. 

Another common sign of this is when you hear that knocking sound on your vehicle.

There is not enough exhaust gas to lessen the heat of the chamber. It would result in the air-fuel mixture igniting before the cylinder can get the right position.

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