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You’re driving down the road and having a normal day behind the wheel of your car. You look down on the dashboard to check your gauges and speed, but you notice that a little orange “Check Engine” light has popped on. You know the one, the one we all love to hate, the one that immediately evokes a generally negative array of emotions. Fear, anger, frustration, and anxiety. You make an unplanned stop at your local garage for more bad news. The technician tells you that you have a faulty EGR valve. This is a common part that is shared by all vehicles, from a Honda Civic to a Ram 3500 with a Cummins Diesel. But what is an EGR valve?

What Is An EGR: Mystery Valve Explained

EGR Definition

First, let’s shed some light on the term EGR itself. Simply put, EGR is short for exhaust gas recirculation. This is one of many initialisms used in the automotive industry for a system, or a component within a system, that is part of the complexities of the modern-day automobile. As an emissions device, the main objective of the EGR valve is to enable a controlled redirection of exhaust gases back into the combustion chamber. But why would we recirculate exhaust gases back into the combustion chamber?

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Understanding The Operation Of An Important System

The Earth’s atmosphere primarily consists of roughly 80% nitrogen and 20% oxygen. Generally, it serves us and our engines well. The issue becomes heat. Typically inert, the nitrogen-rich air is exposed to the extremely high temperatures of combustion within the engine chamber and becomes reactive. From this reaction stems the creation of nitrogen oxides, or NOx for short. This is one of many harmful pollutants that are then released into the atmosphere through our exhaust. By recirculating exhaust gases back through the engine’s combustion chambers, the air charge is diluted. With less oxygen in the cylinder, the combustion chamber temperatures are lowered, and the mixture burns slower. Changing the chemical make-up of the air charge and reduction of cylinder temperature is paramount for lower NOx production and cleaner emissions from the tailpipe.

The EGR valve doesn’t open the floodgates and completely inundate the engine with exhaust gas, though. At initial start-up, the EGR valve is completely closed. After the engine is started, the valve is either commanded to open or close, depending on engine load. For example, when the engine is at idle, little to no power is needed. Since there is minimal load on the engine, a similarly minimal amount of oxygen is needed for operation. At idle, the EGR can be up to 90% open, so the EGR flow has increased. At this point, there are lots of exhaust gases entering the combustion chamber, diluting the air/fuel mixture and certainly less oxygen available or needed for combustion. As you drive down the road, however, there is a need for more power. The engine RPMs go up as the engine load increases. Because more oxygen is required for more power, EGR flow decreases, creating a more oxygen-rich environment for combustion. Broken down: more power needed, more oxygen required, less EGR flow.

Introduction And Integration Of EGR

Humble Beginnings To Federal Mandate

Effective But Not Bulletproof

Simplified, an engine requires three things to run: fuel, air, and a spark. But that’s just the foundational operation. To maintain compliance with today’s strict emissions regulations, complicated engine management systems, along with intricate electrical components, are in place to keep an engine from emitting as many pollutants as possible. Things have gotten so much better in the way of efficiency and emissions, but with all the great advancements in the cleanliness of the internal combustion engine, those advancements do come with some problems. Emissions systems are notorious for being problematic and are often the culprit for the dreaded orange glow of the troublesome check engine light.

EGR Problems: What To Expect When Problems Arise

Common Causes Of EGR Failure And Associated Symptoms

Since the EGR valve itself lives a bit of a rough life, enduring heat cycle after heat cycle, and managing scalding hot exhaust gases, they are prone to some common failures. Most notable is probably carbon buildup from the exhaust gases that can accumulate in the ports of the valve, causing exhaust flow issues within the valve. These deposits can also clog and disrupt the valve plunger itself, causing the valve to remain in the stuck open or closed position. Aside from the illumination of the check engine light, a stuck-open EGR valve has been associated with reduced power, rough idle, and poor acceleration, all due to incorrect air/fuel ratio. When an EGR valve is stuck shut, such symptoms as a high concentration of unburnt fuel in the exhaust, and high combustion temperatures have been experienced. These two issues can also have a negative effect on some exhaust components, such as catalytic converters and oxygen sensors. Engine knocking or detonation can also be a result of high cylinder temperatures. Depending on the system, loss of engine vacuum due to cracked or dry rotten hoses and torn vacuum diaphragms are also very common issues for some vehicles. These problems can also cause similar driveability issues and EGR system failure. These problems, of course, all result in loss of fuel economy and engine efficiency. On the bright side, the average cost for replacement of a bad EGR valve ranges from $420-$560. Certainly not the most costly or difficult repair on a late model vehicle.

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FAQs

What happens when an EGR goes bad?

This can lead to a rough idle, lack of power, poor acceleration, high engine temperatures, and engine knocking, to name a few. These symptoms are primarily the effects of an incorrect air/fuel ratio caused by the EGR valve being either stuck in the open or closed position, or the EGR valve itself is clogged. Other factors can contribute to EGR malfunction, including a compromised vacuum source or electrical/wiring problems. In the event of a malfunctioning EGR system, it is extremely important to seek the advice of a trained automotive technician or reputable repair facility that has professional diagnostic equipment and knowledge to properly diagnose and repair these complex systems.

Can a diesel run without an EGR valve?

Yes, diesels can run without an EGR valve. Older diesels didn’t even have an EGR system. It wasn’t until around 2003 that EGR systems started to show up on diesel pick-up and commercial trucks. In 2007, it was federally mandated that all diesel trucks with a GVW of 8,500 pounds or more must be equipped with an EGR system. Of course, these older trucks would not come close to passing a present-day emissions test. So yes, they could run without an EGR; they were just “dirty.”

Does removing EGR increase power?

Yes, removing the EGR can produce more power. By removing this vital component of the vehicle’s emissions system, a cleaner, more oxygen-rich air charge is introduced into the cylinder, creating more power. However, every engine would react differently as there is no baseline horsepower gain. Above all else, it is highly illegal if a vehicle’s engine came with an EGR system from the manufacturer.

Can a car run without an EGR valve?

A car does not need an EGR valve to run. However, to be compliant with federally mandated emission regulations, a car that came from a manufacturer with an EGR system in place must have an EGR valve. If an EGR valve is removed – although illegal, the car will not run unless properly tuned.

Sources: Delphi , TheCostGuys , CatalyticConverterSolutions , FuelTechExperts