Auto Anatomy: EGR Valves

  • EGR Valve Working
  • Causes of a Failed EGR System
  • Symptoms
  • Fixes
  • FAQs

Since air contains nitrogen, oxygen and inert gases, a human breathes nearly 78% nitrogen from the air alongside oxygen. Besides, a car needs air to burn the fuel. That said, if the engine combusts the air-fuel mixture at high temperatures, it can produce nitrogen oxides (NOx), which is harmful to the environment. However, conventional vehicles come equipped with exhaust gas recirculation (EGR) valves.

The valve improves fuel efficiency and reduces the NOx ofconventional cars. But how does it work? Let’s find all the details on the EGR valve, its working and the symptoms of a clogged valve.

How Does an EGR Valve Work?

Functioning of the EGR valves
An EGR system circulates the exhaust gases in the engine’s combustion chamber to reduce the temperature

The EGR valve is a component in the engine’s intake manifold. Controlled by an engine control unit (ECU) or car computers, the function of an EGR valve in the car is to regulate the flow of exhaust gases into the intake manifold.

It receives signals from the ECU to recirculate the optimal amount of exhaust gases. That said, it increases the engine efficiency. At a steady acceleration, the valve opens and allows the exhaust gases to flow into the intake manifold. Then, these gases mix with the fresh air-fuel mixture. 

Since exhaust gases contain low oxygen content, they are difficult to burn. It reduces the engine combustion temperature. With lower combustion temperatures, the EGR valve helps inhibit the nitrogen oxide (NOx) formation. 

Different types of car sensors, such as engine load, temperature and speed sensors, send signals to the ECU. This helps function the EGR valve accordingly. Moreover, the load will be high when climbing the hill. In that case, ECU sends signals to close the EGR valves. This allows the engine to operate at higher temperatures and produce optimal performance.

Reasons Behind EGR Valve Failure

Reducing nitrogen oxide and improving vehicle performance and fuel economy, the EGR system can be subject to malfunction. Before we delve into its symptoms, let’s learn about the causes of EGR valve failure.

Carbon Buildup and Clogging

Over time, carbon can accumulate on the valve and its passages, restricting proper operation. This carbon buildup can occur due to incomplete combustion and the recirculation of exhaust gases. Besides, the valve can get clogged with debris, dirt or soot. Obstructing the flow of exhaust gases, clogged EGR valves affect the performance. Clogging is a result of poor fuel quality, engine oil contamination or general wear and tear.

A new EGR valve
Carbon buildup EGR valves can affect the engine performance and efficiency

Faulty Valve Position Sensor

The valve includes a position sensor to monitor its opening and closing. However, if this sensor fails, it gives incorrect valve positioning, affecting the engine’s performance. Electronic issues, wiring problems or sensor failure may contribute to the malfunctioning EGR valve.

Vacuum Leaks

Many EGR systems rely on vacuum pressure to operate. However, the valves won’t function correctly if the vacuum or EGR diaphragm leaks. You can detect vacuum leaks from the causes, including cracked hoses, loose connections or deteriorating diaphragms.

Mechanical Failure

EGR valves can experience wear and tear over time. The wear and tear occurs due to oil contamination or excessive heat. These can lead to damaged seals or sticking valves, causing failure in opening and closing.

Symptoms of a Failed EGR Valve

While these symptoms can indicate various common car issues, here are the symptoms of a failing EGR valve.

A rusted EGR valve
A corroded valve can show signs, such as a check engine light or unusual sounds from the car

Check Engine Light 

A malfunctioning EGR valve often triggers the check engine warning light on the car dashboard. The ECU detects the issue with software calibration that causes unusual opening and closing of the valve. After that, it causes the check engine light to illuminate.

Poor Engine Performance

A failed EGR valve can cause rough idling, stalling or hesitation during acceleration. It may also become a cause of sluggish acceleration. These performance shortages happen due to the malfunctioning EGR valve that causes a bad air-fuel ratio. 

More NOx Emissions

Since the engine won’t be at the best performance due to EGR valve failure, the engine temperature will soar. That said, it will produce NOx emissions and pollute the air. It is to be noted that nitrogen oxides are very hazardous to health.

Excessive Exhaust Smoke

With uncontrolled functioning of the valve, the intake manifold receives an uneven air-fuel mixture. You can see white, grey or black smoke coming out from the car. While it can be due to several other issues in cars, you can check what the different car exhaust smoke tells.

Knocking or Popping Sound

You should not ignore car sounds. These sounds tell about the car problems. That said, a malfunctioning EGR system causes a knocking or popping sound due to the carbon buildup in the engine. 

How to Fix an EGR Valve

A malfunctioning EGR valve causes multiple problems, such as poor performance or excessive emissions. For that reason, it is essential to fix it. Here’s how to fix it.

Troubleshooting Codes

Check the troubleshooting codes using an OBD scanner. If you receive the car diagnostic codes from P0400 to P0408 or P1403 to P1406, that means the EGR system is malfunctioning. These codes indicate the exhaust gas recirculation flow problems, such as excessive or insufficient flow or solenoid problems. 

A new EGR system with wiring and connection
You must replace the EGR valves to reduce the emissions from the car

Steps to Replace the EGR Valves

After checking the codes from the OBD scanner, you can replace the failed EGR valves. Here are steps to replace it:

  • Remove the engine cover and remove the electric connections and cable on the valve
  • Inspect the EGR mounting surface since a failed system is a cause of carbon buildup or corrosion
  • Clean the mounting surface and supply port of the valve
  • Take a new EGR valve with the bolt holes and gasket
  • Fix the valve and fasten the screws according to the manufacturer’s recommendations
  • Connect the electric cables and connections
  • Use a car diagnostic scan tool to recalibrate the system and reset the check engine light.

You must recalibrate the system for accurate opening and closing of the valve to achieve better vehicle performance.


What Happens When the EGR Valve Goes Bad?

You can detect multiple symptoms of a failed EGR valve. For instance, poor engine performance, different car smoke, knocking sound, and higher engine temperature are due to the bad EGR valve. Moreover, a failed exhaust gas recirculation valve can be a reason behind car temperature gauge fluctuations.

CAN EGR be Cleaned?

Yes. You can follow the steps to clean the EGR valve. It is necessary to clean the EGR valve after the car achieves the 50,000 mileage mark. 

These were all the details about the EGR valve. You must ensure that the EGR valve is functioning properly when you buy a used car in the UAE. Besides, it can cause the car to start for a second and then die due to the uneven air-fuel ratio.

Keep reading the dubizzle autos blog to learn more details about the car’s essential components.