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What is an EGR Valve: Everything You Need to Know

What is an EGR Valve

An exhaust gas recirculation valve, usually known as an EGR valve, is part of your car's exhaust system. It exists to help reduce the pollutants that your car puts out in the exhaust. This is part of the systems that help reduce greenhouse gases and toxins in the air that contribute to things like smog. It’s all part of the push to keep cars as environmentally friendly as possible.

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Your engine burns fuel at a very high temperature, and sometimes it burns incredibly hot. When it gets somewhere over 2,500 degrees Fahrenheit your engine will start producing what is called nitrogen oxides. This is an unavoidable consequence of burning anything at that high temperature. Your engine intake manifold draws in air from outside to help the combustion reaction. Air is made up of nearly 80% nitrogen. When combustion happens at high enough temperatures, one of the by-products is the production of nitrogen oxide which is extremely toxic and bad for the environment. In order to prevent your engine from producing this toxic by-product, the EGR valve is in place to keep the temperature at that optimal 2,500 degrees for combustion.


When combustion occurs at or below 2,500 degrees there are still pollutants made by your engine, such as chemicals like carbon monoxide and carbon dioxide, but those are considered more manageable and easier to deal with than the nitrogen oxides that you'll get at higher temperatures.



How an EGR Valve Works


Much of the gas produced by a combustion reaction in your engine is carbon dioxide. Carbon dioxide does not burn, but that is used thanks to the EGR valve. The EGR valve recirculates the carbon dioxide back into the combustion chamber which reduces the temperature of the combustion reaction. Because it can't burn, the temperature can't get high enough to reduce those toxic nitrogen oxides. 


When the EGR valve is not working the way it's supposed to, that means the CO2 isn't being properly recirculated back into the combustion chamber. Either there's no CO2 making its way to the chamber at all, or it's being introduced at the wrong time or in the wrong amounts. Whatever the case, the EGR valve is not functioning, that you're not able to maintain the proper temperature of the combustion reaction. That not only creates more pollutants in the form of the nitrogen oxides, it also potentially means your engine will be overheating and causing additional damage.


Signs of a Bad EGR Valve


Your EGR valve has ports in it but allow the gases to pass through. One of the main ways that this can end up failing is when the ports get clogged. Dirt, grease, and debris can all get stuck in the EGR valve reducing its overall effectiveness or clogging it completely. That means that potentially the EGR valve could just need a good scrub clean to get working again rather than having to replace the whole thing. If it is faulty though, failing or broken completely, you'll notice some of these signs that indicate you should get a mechanic to take a look at it and see what's going on.


Gasoline Smell


If the EGR valve is not working correctly you may notice the smell of gas in your car. This is a result of your car burning more fuel than it's supposed to because the air-fuel mixture is off. This happens thanks to the CO2 levels not being where they're supposed to be. If you start burning more gas than necessary, the smell will find its way into the cabin of your vehicle. Not only does this mean you were sacrificing fuel economy as a result, it's also a potential health hazard as well. Breathing in excess fumes can cause headaches, nausea, and dizziness. That would be very dangerous if it happens behind the wheel on a regular basis and could lead to accidents. If you smell gas in your car, you need to get it checked out immediately.


Rough Idling


There are a number of things that can cause a rough idle in your car, so you'll need to work on a process of elimination to figure out exactly what the cause is. If you're experiencing some of these other symptoms along with rough idling, there's a good chance your EGR valve is behind it. If the valve is stuck in the open or closed position on a regular basis then the exhaust gases from your combustion chamber are going to be in the incorrect portions. That’s going to throw your engine's performance off, and lead to similar issues like lurching, vibrating, and general rough idling.


Poor Engine Performance


When your EGR valve is not working the way it's supposed to, there's the potential that the overall performance of your engine is going to suffer as a result. That's going to mean a reduction in power output and reduced acceleration compared to what you're used to. Obviously there are a number of different things that can go wrong in your car that can cause this to happen, but when the EGR valve is responsible it causes the fuel-air ratio in your combustion chamber to be off balance. When your car isn't burning the exact right fuel-air mixture, it's not going to be producing the exact power that it was designed to handle. When the combustion occurs at the wrong time, or if your air fuel mixture is too lean or too rich, the entire performance of the engine goes down as a result. You'll also see the effect of this when you head to the pumps as you're going to be having to pay for gas more often. 


Failed Emissions Tests


This is a much more rare symptom of something going wrong with your EGR valves as not every state even requires you to take an emissions test. But if you do have to take one and you fail there's a good chance that your EGR valve is the problem. This will be a result of it not filtering those toxins we mentioned out of your exhaust, which can cause you to not pass the test when you have it done.


Check Engine Light


Obviously this one is harder to diagnose than most of the other symptoms and so many things can cause the check engine light to go off on your dashboard. One way to find out for sure that the EGR valves the problem is to plug in an OBD2 scanner and run the scan to see why the light one off. This is what the mechanic will do when you take it to the garage, but you can do it yourself if you have a scanner at home. Luckily you can pick up ones on sites like Amazon.com fairly cheaply, usually under $30. It's handy for diagnosing any issues that come up with the lights on your dashboard since it can be very hard to know precisely what the warning is supposed to mean in the first place.


Typically, when the check engine light comes on as a result of an EGR valve problem it's because the valve is either stuck in the open or the closed position. That will tip the car's computer that something is wrong and will send a code that you can read with the OBD2 sensor.


Can I Replace My Own EGR Valve?


It's definitely possible to do this repair job on your own if you have an EGR valve to replace the old and laugh. As we said earlier, it's best to check your old valve to make sure it's not just dirty. If that's the problem, you won't need to invest in buying a new one. If you had to AutoZone, you'll see that a new EGR valve can run you anywhere from $40 all the way up to $500. It very much depends on the make, model, and year of your vehicle.


Replacing the EGR valve is an intermediate kind of repair job. If you've never done DIY car repairs before, we wouldn't really recommend this as a place to start. If you are comfortable doing some home auto repairs, you may be able to take on this task on your own. The best thing you can do is Google some walkthroughs for your make and model of car to find out exactly where the valve is located and how to replace it.


An even better method of getting this job done is to check out the videos that are online that can show you exactly how to do the job. 30 years ago, this kind of job would only be done by a mechanic because most people wouldn't even be aware that they have an EGR valve let alone where to look for one or how to put a new one in. Thanks to YouTube, there are countless videos made by skilled mechanics who have decades of experience that can walk you through any repair job. 


A video like this one will walk you through step-by-step what to do and you can see exactly what the mechanic is talking about and what you need to do yourself, plus you can rewind and go over steps if you feel like you missed anything. There's never been a better time to do DIY car repairs then now. Still, if you’re feeling a little intimidated by the job is no reason to not take it to a mechanic to ensure it's done precisely the right way. As we said, this is not a beginner's kind of repair job at all.


The Bottom Line


The thing about an EGR valve is that for the most part, people don't think they need one in order for their cars to operate properly. But it is an integral part of how your engine functions. Even though it's a part of the exhaust system, it's important for maintaining your engine’s temperature so that everything operates at peak performance and combustion occurs at the appropriate time while limiting the amount of toxic chemicals that are being produced and pushed out into the environment. 


This is one of the few parts of your vehicle that you need to maintain not just for the benefit of your vehicle, but for the benefit of the environment that we all live in. Not everyone is as concerned about the environmental impact that their vehicle has as some others, but it is something that we all take part in and we all need to be aware of. The fact is your car puts out a fair amount of pollution. They all do, that’s a given when you burn fossil fuels. That's why this is important because, even though your individual car isn't causing an insurmountable level of pollution in the world, you need to remember how many cars are on the road at any given time. In fact, some estimates suggest there are 1.4 billion cars on the road today. If every single one of those cars has a faulty EGR valve and is putting out toxins like nitrogen oxides into the air, we are in a bad place.


Most of us don't think of our vehicles in terms of their Global impact, and of course we don't really need to do that very often, but it is something to keep in the back of your mind when you're considering what to do about an EGR valve if you find out that yours isn't working. It's just one small thing that can help have a big impact overall if every single driver is on board with keeping these pieces of Technology functioning.


Whether you plan on handling the job of repairing a malfunctioning EGR valve on your own, whether you're getting it fixed by professional mechanic, or whether you're just curious about what one does and how it affects the overall performance of your vehicle, it's good to know as much as you can about every part of your car. 


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