Integral to the vehicle’s engine management system, the aptly named exhaust gas recirculation valve, or EGR valve for short, recirculates finely metered quantities of exhaust gas to the engine intake system for increased engine efficiency, reduced fuel consumption, and lower NOx emissions.
With growing pressures to reduce emissions, the EGR valve will play an increasingly important role moving forward. It’s important to know what it does, why it fails and how to replace it when it does.
What is EGR Valve?
EGR stands for exhaust gas recirculation, a vehicle emissions control concept used in both gasoline and diesel engines. The EGR valve which works differently depending on how old the car is and whether it uses gasoline or diesel fuel is a key component of a car’s exhaust system and engine health.
The EGR Valve is one of the vital components of your vehicle’s engine. EGR stands for exhaust gas recirculation. Therefore, the valve is a type of emissions-control device that is located between the exhaust manifold and the intake manifold.
This is normally closed by the time you turn on the engine. However, once the engine heats up and under load, the valve will eventually open up. This process enables a certain amount of burned exhaust gas to enter the intake manifold before it re-introduces fresh air into the engine.
While this step might seem counterintuitive, it makes it possible for modern engines to run efficiently and for longer. The combustion mix maintains the lower combustion temperature that keeps the NOx emissions low, as well. The exhaust fumes are definitely beneficial but they can clog the valve once they accumulate over time. This can cause clogs on the valve and a host of other engine problems.
Experts agree that the valve must be cleaned every few years. You can use the 50,000-mile gauge as a point of reference for when you need to do the cleaning.
Related: What is Engine Valve?
How does an EGR valve work?
The EGR system works by returning a small portion of exhaust gas to the engine’s combustion chambers through the intake manifold, lowering combustion temperatures and therefore reducing the amount of NOx emitted. The EGR valve is the main component of the EGR system and it’s normally closed.
It connects the exhaust manifold to the intake manifold and is controlled by either a vacuum or a built-in electric step motor. The function of the EGR valve is to control the flow of exhaust gas being recirculated depending on the engine load.
The majority of modern vehicles incorporate EGR valves into their design to reduce NOx emissions and therefore meet stringent emissions regulations. EGR systems recycle a portion of the exhaust gas back into the combustion chamber, where it combines with fresh intake air.
This lowers the amount of Oxygen and increases the water vapor content to the combustion mixture which reduces the peak combustion temperature. Because more NOx is created as peak combustion temperature rises, the EGR valve effectively reduces the amount of NOx produced by the engine.
The EGR valve begins working once the engine has started, attained the correct operating temperature, and the vehicle’s speed increases. Gradually, the EGR valve regulates the flow of exhaust gases.
Once the vehicle slows down and the engine stops, the EGR valve will return to its closed position and prevent the flow of exhaust gases.
Types of EGR valve
Although there are several types of EGR valve earlier systems use a vacuum-operated valve, while newer vehicles are electronically controlled the main types can be broadly summarized as:
- Diesel high pressure EGR valves divert the high-flow, high-soot exhaust gas before it enters the diesel particulate filter the soot can combine with the oil vapor to create sludge. The gas is then passed back to the inlet manifold either via a pipe or internal drillings in the cylinder head. A secondary valve is also used to help create a vacuum in the inlet manifold as this is not naturally present on diesel engines
- Diesel Low pressure EGR valves divert the exhaust gas after it has passed through the diesel particulate filter this gas has a lower flow but is almost completely clean of soot. The gas is then passed back to the inlet manifold via a pipe.
- Gasoline EGR valves divert the exhaust gases, much like the high-pressure diesel equivalent. The vacuum created by cylinder depression, draws the exhaust gases in and the flow is regulated by the opening and closing of the EGR valve itself.
- Vacuum operated EGR valves use a vacuum solenoid to vary the vacuum to the diaphragm and, in turn, open and close the EGR. Some valves also include a feedback sensor to inform the ECU of the valves position.
- Digital EGR valves feature a solenoid or stepper motor and, in most cases, a feedback sensor. These valves receive a pulse width modulated signal from the ECU, to regulate exhaust gas flow.
When Do You Know It is Time to Clean?
Now that you understand the function of the EGR valve and why it might need cleaning, the next step is to determine when cleaning should be done or necessary. This is an important step to know because a lot of people end up throwing away their valve when in fact a little cleaning could still restore its function.
The EGR Valve is emission-related so the symptoms are not too obvious. But if you know what to look for, then you can tell that it is time to clean your valve. These are some of the symptoms to look out for:
- Difficulty in starting the engine
- Rough idle
- Engine vibration
- Poor acceleration of the engine (during drive)
- Engine easily running hot
- Engine ‘ping’ when under load
- Smell of unburned gas fumes
- Decrease in gas mileage
Finding the EGR Valve
Depending on your car’s make and model, your engine may be using one of three common types of EGR valves: vacuum controlled (older models), electronic-vacuum controlled valve (newer models), or the new electronic controlled digital valve.
You’ll locate the valve towards the top or side of the engine. However, one or more components may obstruct your view.
- Older vehicle models use a semi-flat, round thick metal disc about three inches in diameter. You’ll see a thin vacuum hose connected on top.
- Newer models use a similar valve with a small box (sensor) on top along with an electrical harness.
- Still other models use a cylinder or block configuration for the valve with attached sensors and an electrical harness.
Look around the side of the cylinder head (top area of the engine) for the valve. Check near the throttle body, firewall, or intake manifold. If you don’t see it, search for your EGR valve online by going to an auto parts store website and entering your car’s make, model, and engine size to look for the valve.
Most auto parts stores will show the picture of the EGR valve that applies to a particular vehicle make and model for quick identification. Look at the picture and you’ll know exactly what you’re looking for.
Or, better yet, consult the repair manual for your particular vehicle make and model. You can buy an inexpensive aftermarket repair manual at most auto parts stores and online.
The manual tells you not only the location but provides illustrations and photos of the valve and related components, troubleshooting procedures, and the necessary steps to remove and replace EGR system components like the EGR sensor, vacuum hoses, and pipes.
How to Remove the EGR Valve
After locating the valve and moving accessories out of the way to gain access to it, it’s time to remove it.
- Some valves have a thin vacuum hose attached to it. Carefully disconnect the hose from the valve. Check the vacuum hose for splits, softening, hardening, or cracks. If necessary, replace it. Damaged vacuum hoses cause poor EGR valve operation and EGR system failure.
- Follow the vacuum hose you just disconnected to the component attached at the other end, and inspect any other hoses connected to that other component as well, if any.
- Unplug any electrical connectors from the valve.
- Using a ratchet, extension, and socket, remove the valve mounting bolts. You’ll need to unscrew two to four bolts, depending on your particular model. Also, your valve may connect to a pipe coming from the exhaust manifold. To remove the pipe, use an adjustable or crescent wrench or disconnect the pipe at the exhaust manifold.
- After removing the EGR valve, check the valve’s gasket(s). If it still looks in good shape, recycle it. Otherwise, buy a new one. Some auto-parts stores only sell the gasket as part of a new EGR valve. Yet, you can buy gasket paper and make your own. Save the remaining paper for other gaskets you’ll need in future repairs.
How To Clean An EGR Valve And EGR Ports
- Put the vehicle in park and apply the emergency brake. Consult your owner’s/repair manual to locate the EGR valve.
- Turn off the engine and disconnect the battery.
- Inspect all vacuum lines for rips, tears, and holes. Replace as necessary.
- Remove the vacuum line or unplug the electrical connector from the EGR valve.
- Next, remove the bolts that hold the EGR valve to the cylinder head or intake manifold.
- Remove the EGR valve. Be careful to protect the open cylinder head or intake manifold from any debris.
Tools You Will Need:
- Ratchet extension
- Socket set
- Adjustable wrench, if removing a pipe
- New EGR valve gasket, if necessary
- EGR valve or carburetor cleaner
- Dull scraper
- Pipe cleaning wire brush
- Repair manual, optional
- Acid-resistant gloves
How to Clean EGR Valve?
Put on your safety glasses and acid-resistant gloves, you’re going to remove carbon deposits from the surface, entry and exit ports on the valve, and corresponding intake and exhaust ports and pipe.
- Spray carbon deposits with EGR-valve or carburetor cleaner. Immediately wipe cleaner off plastic parts and electrical components still attached to the valve to prevent damage.
- Use a dull scraper and a pipe cleaning brush to scrub carbon buildup. Then use a soft brush to remove the carbon and wipe the surface using a clean rag. Repeat the process as necessary. And don’t gouge mounting and sealing surfaces, or you’ll cause exhaust gases to leak.
- To deal with rock-hard buildup, leave the valve soaking in the cleaning solution for a few minutes. Just don’t let the cleaner touch electronics, electrical components, or plastic parts, or you’ll ruin the valve.
- Repeat step 3 to fight stubborn carbon deposits. Some people leave the valve soaking in the cleaning solution overnight, but fumes emanating from the strong chemicals in the cleaner gradually destroy sensitive valve parts, so do it at your own risk.
- If you know carbon deposits remain inside the intake manifold, apply the EGR valve cleaner through the intake manifold, read the instructions on the product’s package. This will also help remove carbon from the intake valves. Seafoam is another popular product for this purpose. Or, if you prefer, take your car in for a carbon cleaning service.
- Once you’ve removed all the carbon buildup and cleaned each passage and sealing surface, reassemble all the components, including the gasket.
- Put everything back in place and check that the symptoms have disappeared.
How To Clean EGR Ports?
This part of cleaning the EGR system is oftentimes overlooked and can make any repairs made to the system invalid due to a restricted, or in some cases completely blocked, passage(s) in the ports themselves. Always check and clean these ports when servicing the EGR system. Here’s a helpful video of the following process.
- Note where the EGR Valve connects to the intake manifold or cylinder head. This is where the largest amount of carbon will be built up due to the change in temperature as the hot exhaust gases come into contact with the cool intake manifold gases. This will be where you start the EGR passage cleaning procedure.
- Start by spraying the cleaner into the port.
- Then use a pick or a repurposed wire coat hanger to push through the carbon.
- Continue this until you can spray cleaner all the way through the passageway. Tech Tip: Some passageways may not appear to be passageways at all due to being completely block. In this case, poke through and slowly work at cleaning the carbon away.
Below are some examples of clogged EGR ports.
- Some vehicles may have multiple cleaning ports for the EGR system. Reference your vehicle-specific service manual to see if this applies to your vehicle. If it does, remove the access plugs and clean these ports in the same fashion as above.
- After all the ports are clean and the EGR valve is clean, reassembled all removed parts, clear any codes, and test drive to see if you have resolved your problem. Congratulations, you have now cleaned your car’s entire EGR system!