Bad EGR Valve Symptoms

Do you suspect that the EGR Valve of your Car is faulty? Every modern car comes fitted with an EGR valve. When it gets clogged or damaged, it results in a poor running engine.

Clogged EGR Valve needs cleaning

Now if you’re completely new to the world of automobiles, or if you’ve not spent much time tinkering around with your toys, you may not have heard of EGR. This is where most mechanics may try to take advantage of the vehicle owners. But don’t worry, we’ve got you covered.

Symptoms of faulty EGR valve include: Poor engine performance, Engine check light, Smell of unburnt Fuel from exhaust, Failed emissions test, and Rough idling.

How you can find if your EGR is actually faulty? and what may be the reason for this? You will also get to know everything there is to know about this simple yet complex vehicle component, so let’s jump right into it.

What is an EGR Valve?

The EGR valve or the Exhaust Gas Recirculation valve can be found in most of the modern fuel-powered vehicles(petrol and diesel), and the purpose of these things is to help reduce engine emissions, by sort of “recirculating” some of the exhaust gas back into the engine.

Over the past few years, it has been proved that there have been drastic changes in climate due to pollution, and the contribution of automobiles to this pollution is very high.

The government has in turn set certain regulations for vehicle manufacturers, and one of them is the addition of the EGR. So almost every vehicle you see on the road today likely has an EGR fit inside.

EGR Valve helps to reduce NOx emissions

Merits to an EGR Valve

An EGR valve will reduce the temperatures in the cylinder by considerable amounts. Not getting too technical, here’s a quick working principle on how engines work – they basically take in air and mix it with fuel at a certain temperature and pressure, and this mixture is then ignited to produce energy that moves the wheels of the vehicle.

However, this process creates a lot of heat, and too much heat is never good. With the help of an EGR valve, a portion of the exhaust gas is allowed to pass through the inlet manifold where it displaces a certain amount of oxygen from the air, thus keeping the engine cooler and more efficient.

High temperature and the excess amount of oxygen are the main sources of NOx (pollutant exhaust gas) formation. And from the above observation, it can be clearly stated that an EGR effectively reduces both excess oxygen content and reduces the engine temperature as well.

It also helps in reducing the number of nitrogen emissions produced. Exhaust Gas Recirculation (EGR) is one of the simplest techniques that can be easily applied in a way to suppress NOx formation.

How does an EGR work?

There is a lot of air around us which is picked up by the engine’s intake manifold. Air is made up of roughly 20% Oxygen and 80% Nitrogen. There are also other components present in really small quantities, but the major reacting components are oxygen and nitrogen. Learn how to take care of Turbocharged Engine

What does an EGR valve do? While the oxygen reacts with the fuel, at high temperatures (around 25000F inside the engine), nitrogen burns to form an increased rate of NOx emissions. The EGR’s role here is to send the gases which are being exhausted back into the combustion chamber to reduce the temperature and also suppress the formation of NOx almost entirely.

Play Video above to Learn How to Clean EGR Valve in your Car


EGR System Tech Evolved Overtime

Modern diesel and petrol vehicles engines use an array of EGR valve configurations. Before learning what causes EGR problems, it would be better to know which kind of EGR your vehicle sports, so the problem can be narrowed down further with relative ease.

Old vehicle models

In older generations of vehicles, EGR valves would occupy more space owing to their thick round design. They are usually made with a diameter of 3 inches and can be found on the upper side of the engine.

On these past models, there is a vacuum hose that runs the EGR valve. A tube is used as a connection between the upper part of the EGR and the carburetor. The metal disc can be found in the valve, containing a vacuum diaphragm, plunger, and spring setup.

Semi modern vehicle models

Most manufacturers in the past decade have an electronic vacuum EGR valve which is placed inside a cylinder or a small block in some cases. The valve is made in such a way that it operates similarly to the ones which have been fitted in the older models.

It can go unnoticeable because instead of tubes, electronic solenoids are being connected through the vacuum lines and the valve too. This helps the EGR position sensor to communicate faster and more efficiently with the ECU.

Newer models

In present-day vehicles, the EGR setup is similar to the above-mentioned tool, except that the vacuum control lines are replaced by a digital valve, which drastically improves performance and reliability.

Radical design

There are a lot of other models that replaced the EGR valves with EGR jets – which comparatively take in a lesser portion of the exhaust. They can be found in future car models, although the chances that you’ll run into them is pretty less. Some of the high efficient engines like those which have variable valve timing do not require EGR at all.

Important Tip: It is also pretty important to know which kind of EGR you’ll be dealing within your vehicle. Generally, your mechanic would inform you about this, but in case you ever have the necessity of buying a replacement by yourself, just know that there are five very easily distinguishable types of EGR valves – Back Pressure EGR valves, Vacuum controlled valves, Electronic vacuum control EGR valves, EGR jets, and Digital EGR valves.

5 Symptoms of Bad EGR Valve?

EGR faults can cause a lot of problems. The fuel economy of the vehicle is hit, for instance, and this will cause high fuel consumption by the vehicle, increasing the chances of more carbon deposits, higher emissions, and faulty injectors and damaged sparks.

So it is really essential that you get a faulty EGR checked as soon as possible. While there can be a lot of bad symptoms, the following are the major red signs that tell you your EGR valve is in need of a check-up.

1) Poor Engine Performance

There are a lot of issues when it comes to bad EGR valves and the first and perhaps most frustrating problem is the performance of the engine. There is a big chance for you to experience acceleration difficulties and even an overall reduction in the power of the engine when you step on the gas pedal. This can also happen due to bad fuel filter

This can happen due to the air-fuel ratio being heavily rich or heavily lean[1]. It is because of this that the engine may require more fuel than normal in almost every situation you’re facing while driving. This will really take a hit on your wallet as fuel prices aren’t showing signs of reducing either

2) The Engine Warning Light

You must always check the engine indicator which will in most cases glow up on the dashboard if the EGR valve fails in any case(unless you’ve somehow damaged that as well, in which case you’ll need to replace that as well).

We won’t get too technical here, but just know that the Engine warning indicator will turn on when the ECU senses any issues with the engine or its directly associated components.

The EGR is directly connected to the engine, and so any irregularities in its functioning(opening, closing, etc.,) will be immediately sensed by the EGR valve sensors.

3) Smell of Unburnt Fuel

Now that the EGR valve is not functioning properly, the engine is taking up more fuel than it is supposed to, which will eventually cause more hydrocarbons to leave the tailpipe. This will increase the amount of fuel odor, and to such an extent that you can feel it inside the car if your AC is not in recirculation mode.

It’s a very irritating phenomenon and can be terrible for your health. This is a sure sign that something is wrong with the engine.

4) Failed Emissions Test

If you are in a situation that requires you to test for increased emission levels every 6 months, then it might be a chance that you have a faulty EGR valve. Although this test may not accurately predict the state of the EGR, if you fail your emission test, it’s a healthy practice to have the vehicle’s EGR valve checked out by a professional.

5) Rough Idling

Rough Idling happens when the engine has a faulty EGR valve. In this case, the valve will remain stuck in either an open or closed position as long as the problem is fixed. This might also be an indication that there are a few too many exhaust gases entering the combustion chamber.

This will disrupt the air/fuel mixture that’s required for proper idling of the engine. You’ll then notice rpm needle fluctuation as the car struggles to maintain idle rpm.

EGR valve stuck in an open position creates a vacuum leak that causes inefficient combustion. A valve that’s stuck in a closed position increases nitrogen oxide emissions, which disrupt engine timing, leading to engine knock.

Three EGR Valve Faults:

There are only 3 types of bad EGR valves, and each of them shows different symptoms. The EGR valve can become faulty in two different ways. It can either stay close all the time or stay open all the time.

There are also some cases in which it can remain clogged in an idle position because of all the unburnt carbon deposits. So let’s go over these problematic cases and learn how to diagnose them.

1) When the EGR valve is stuck open

In a case where the EGR valve is in an open position, there are chances for it to create a vacuum leak. This leak will result in incomplete combustion, which is usually the initiator for rough idling and fluctuation in the rpm needle.

Diagnosing the EGR stuck at open position

When the vehicle is parked in an idle position, what you have to do is look for a plunger shaft, and physically check for the valve’s positioning. If that isn’t a feasible option, there are several OBDs or On-Board Diagnostics devices (more on this later) that can be plugged into the vehicle and checked for errors.

Error codes like P1406 and P1404[2] can be seen in cases where the valve is stuck in an open position. You would then have to remove the plug and fill the empty spaces with a carbon cleaner.

In some other cases, if the working fluid inside the EGR leaks when the world is placed upside down or when it is held open, all you have to do is use a valve cleaning kit and then move on to pull out the vacuum from the valve.

2) When the EGR is stuck closed

As we talked about earlier, if the EGR is in a closed position and remains stuck, a large amount of NOx emissions is not far away. This kind of vehicle might even produce knocks[3]. This will deem for a different kind of disruption in the engine timing, and of course, result in excess wear and tear. This is definitely not something we want.

Diagnosing an EGR valve stuck at closed position:

In a parked position if the car revs up, you must always check the EGR valve that moves. When the EGR is stuck closed the errors P041 and P1406 may show up on the OBD ECU scan tool.

The knocking sound which you might hear can be a sign that the valve has already been shut down. You will have to remove the valve manually. A valve kit at this point will come in handy, or you could always go to your mechanic if you don’t want to get your hands dirty.

3) Clogged EGR valve

Unburnt carbon deposits can also prevent the EGR valves from staying in an ideal position. This kind of issue can lead to rough idling. This can only happen in severe cases when the automobile is in its start position. Clogging of EGR valves prevents exhaust gas from recirculating, and this usually happens after crossing speeds of 30mph(45kmph).

Diagnosing and Fixing a clogged EGR

Errors P1404 and P1406 show on the ECU scan tool telling that the EGR valve is blocked. All you have to do is remove the valve and clean it using a valve cleaning kit or throttle body cleaner to remove the debris.

If you feel like you might not have the experience needed to fix the issue or if you’re not able to get your hands on proper equipment, then a mechanic’s assistance is probably the best idea.

Smog Test is also a good way to detect clogged EGR Valve

If the EGR valve clogs or is completely being blocked off, it can no longer re-burn harmful emissions inside of the combustion chamber. The NOx emissions will flow unregulated through the combustion chamber and out of the exhaust pipe.

The excessive NOx emissions will show up during a smog test and cause failures. In addition to the NOx emissions, a clogged EGR could enrich the fuel mixture and produce excess amounts of HC (hydrocarbons) and CO (carbon monoxide).

Check Engine Light for Diagnosis

A clogged or defective EGR valve will trip a “Check Engine” or “Emission Control” light on the dashboard. The owner will have to take his vehicle to a certified test and repair station that has a code scanner (OBD diagnostic tool).

The scanner will then be plugged into the vehicle’s computer system, and a trouble code will be identified. If the EGR valve represents the system failure, the code number will specifically identify the EGR as the failed component.

When the engine overheats because the EGR has failed, more lubricating oil can potentially enter the combustion chamber and the diesel engine may start running on lubricating oil even if the fuel supply is cut off. A diesel engine may then begin to run on its engine oil instead of fuel.

The driver may be unable to switch off the engine in any other way than by forcefully stalling it. Eventually, the engine sucks away all the lubricating oil and the engine might disintegrate.

Cost of Repairing/Replacing EGR Valve

Most EGR valve-related problems can be fixed just by cleaning it with a throttle body cleaner. Cleaning out the carbon buildup should make it work smoothly without getting stuck in the open or closed position. So, you’ll need some elbow grease and a throttle body cleaner to do this 20-minute job.

If you need to replace the EGR valve then can cost anywhere between $40 to $800 depending on your vehicle model (Check exact price on Autozone.com). Installation labor charges should be around $70.

Safety Tips:

Most mechanics will likely be up for the task of replacing an EGR easily because it doesn’t usually require a lot of technical expertise. But if ever you face the problem of having to do it yourself, make sure you use proper precautions and safety procedures during the whole operation.

It is a good practice to take pictures of the engine bay and the connections from the EGR valve.

The EGR cooler must be allowed to cool down and then disconnected from the battery. You will have to wait a few minutes for the electrical system to discharge completely else there are chances you may get a slight shock, or worse, damage the battery.

The process of isolation of the battery terminals should also be done to prevent the shorting (Remove negative terminal first, then positive to prevent chances of short-circuiting but accidentally touching positive terminal to chassis). But before removing anything you should check the replacement of the EGR valve that you have bought. It may look identical to the old one, with the same connections and also the fittings, as most EGR valves have the same configurations. Ensure that the part no is same.

The EGR valve might also have vacuum pipes fixed to it. Before twisting and pulling off the pipes with brute force, be sure to label them. Most manufacturers already have them labeled, but in the off chance that you don’t see a label, fix one.

Be extra careful not to break them or even stretch them out too much. If in case they have been cracked or damaged you have to make sure that you replace them with newer spares. These pipes are not uncommon and are not that expensive either, so it’s best that you get new ones.

Once done, you have to carefully take out any electrical connections to them. This can easily be done by the use of hands, because most of them are just hand-tightened.

The valve may be mounted with a sturdy outer body, while also being bolted to the cylinder head. It is because it has hot exhaust gases passing through it at all times. The bolt that is holding the valve may end up being particularly tight as a result. It may be a good idea for you to spread this with a lubricant such as WD40[4]beforehand and allow it to sit for a couple of minutes.

Once you have successfully applied the degreaser over all the bolts, use force to pull the valve and the body out with your hands. There are chances for the valve to get stuck but it should come off with a little push and pull.

Then you have to carefully remove any remnants of an old gasket between the valve body and the cylinder head and clean the interface without allowing debris to fall into the cylinder head in any way if possible.

A new gasket should then replace the old one and this should be fit along with the new valves. A good practice would be using a small amount of high-temperature-resistant silicone sealant is very good as well.

In order to fit the valve back into the engine, just repeat the whole process backward. It may be necessary to reset the engine check light before you start the car and ensure it idles smoothly before taking it for a drive.

Closing Thoughts

The exhaust gas recirculation system can perhaps just be the most important component in the automobile engine. If you understand the way that it works, it will be easy for you to make sure that it is always kept in a good condition which otherwise can cause a lot of problems and it’s, therefore, essential to keep your EGR valve clean and trouble free.

Frequently Asked Questions

Can you drive with a Bad EGR Valve?

Yes, the car is mostly drivable even if EGR valve has failed. However, it won’t run well. You might notice symptoms like Poor engine performance, Engine check light, Smell of unburnt Fuel from the exhaust, Failed emissions test, and Rough idling.

Can EGR Valve be Cleaned?

Yes, most EGR-related problems can be solved just by cleaning the valve thoroughly with throttle body cleaner. It’s very rare that you’d need to replace the EGR unit.

What Does EGR Valve Do?

Exhaust gas recirculation valve helps lower exhaust emissions. Excessive NOx (harmful gas) is released when the engine is too hot and there’s excess oxygen in the combustion chamber. EGR valve reroutes some of the exhaust gas back into the combustion chamber to displace some oxygen and lower engine temperature. This reduces NOx gas emissions.

Also Read: Are Fuel System Cleaners Worth it?

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Siddharth Sharma

Siddharth has always been passionate about Cars and Bikes. He was the kind of kid that always had the latest Auto magazine in his school bag. He had this dream- to become a professional racecar driver. Finally, in 2012 he found himself racing as a rookie driver in the Polo R Cup national racing championship. Over time he had to readjust the sail and get into automotive journalism to continue enjoying machines on wheels.