What Are The 9 Symptoms of a Faulty EGR Valve?

The EGR valve is known for collecting grime due to recirculating the exhaust gases. This means that at some point in time, your EGR valve might become faulty. It’s best if you know the symptoms of a faulty EGR valve and act accordingly. Sometimes, simply cleaning the EGR valve without removing it will do the job, sometimes it won’t.

The purpose of the EGR is to open up and recirculate part of the exhaust gases back into the intake manifold. These exhaust gases help reduce the temperature of combustion. This is super important because nitrogen oxide is formed at high temperatures. So, by reducing the temperature it reduces nitrogen oxide formation.

When it comes to symptoms of a bad EGR valve, it can go in two different directions: Symptoms of a stuck open EGR valve or you can have symptoms of a stuck closed EGR valve. I will now go in-depth and show you what are the 9 symptoms of a faulty EGR valve.

Symptoms of a faulty EGR valve include a check engine light, failed emissions test, engine knock, lack of acceleration, rough idle, fuel smell around the car, bad fuel economy, black smoke from the tailpipe, or engine misfire.

Learn more about engine oil here.

Key Takeaway

What Are The 9 Symptoms of a Faulty EGR Valve?

  • Check engine light
  • Failed emissions test
  • Engine knock
  • Lack of acceleration
  • Rough idle
  • Fuel smell around the car
  • Bad fuel economy
  • Black smoke from the tailpipe
  • Engine misfire

What Are The 9 Symptoms of a Faulty EGR Valve?

What Are The 9 Symptoms of a Faulty EGR Valve

A faulty EGR valve is something that happens more often than we want. It is a hardworking part of the vehicle that is exposed to a lot of exhaust gases throughout its lifespan. This means that carbon buildup is inevitable. That’s why I have done in-depth research and provided you with what are the 9 symptoms of a faulty EGR valve:

1. Check engine light

What Are The 9 Symptoms of a Faulty EGR Valve

The easiest way to figure out if your EGR valve is faulty is by noticing your check engine light on. There are some codes related to a bad EGR valve: P0400, P0401, P0402, P0403, P0404, P0405, P0406, P0407, P0408, P0409. You can read these codes with an OBD Scanner (see prices on amazon.com) or by going to the parts store near you and they’ll most likely do it for free.

2. Failed emissions test

If your car fails the emissions test, you most likely have a faulty EGR valve. This can be due to a stuck closed EGR valve. A stuck-closed EGR will prevent the exhaust gases from coming into combustion. If the exhaust gases don’t come in, the temperature inside the chamber will increase and produce more nitrogen oxide. Therefore, too much nitrogen oxide will fail your emissions test.

3. Engine knock

What Are The 9 Symptoms of a Faulty EGR Valve

The third symptom you might be experiencing if your EGR valve has failed is engine knocking. Engine knocking is when an unplanned mini-detonation occurs during the power stroke in combustion. People describe it as a pinging noise.

A stuck-closed EGR prevents exhaust gases from coming inside of the combustion to cool it down for proper temperature levels. Hot temperature levels inside the combustion can ignite the air/fuel at unwanted times which creates your engine to knock.

4. Lack of acceleration

A lack of acceleration can be a clear sign that your EGR valve is faulty. A stuck open EGR valve can be the cause of this. A stuck-open EGR will continuously exhaust gases back into the combustion chamber. These gases will take up space, therefore limiting the amount of air that needs to enter in order to achieve optimal engine performance. That is why your acceleration is lacking.

While accelerating, the engine needs more fresh air to get its peak performance. More exhaust gas instead of fresh air will also alter the fuel injection rates which will further decrease the performance reasonably. You can and should try to clean your EGR valve without removing it. I have another article that explains in great detail how to do that. Check it out here.

5. Rough idle

Another symptom of a faulty EGR valve is a rough idle. The reason for this is because the EGR is stuck open. It takes up space from the exhaust gases inside the combustion, therefore not leaving much room for air to combust efficiently with fuel. This leads to improper combustion which results in your car having vibrations and rough idle.

6. Fuel smell around the car

If the EGR is not functioning properly, the fuel inside cannot burn efficiently due to disturbed air-to-fuel ratios. This will emit more unburnt fuel into the exhaust thus making a pungent fuel loader. This symptom occurs mostly when the car is first started or when the engine is cold.

7. Bad fuel economy

A faulty EGR alters the combustion efficiency of the engine badly. You might even find yourself in a situation where you need to press more on the gas pedal than usual to go forward. This can make the overall efficiency of the engine go down and affects the gas mileage badly.

See more: Why Is My Car Wasting So Much Gas [9 Reasons]

8. Black smoke from the tailpipe

If your EGR valve is faulty, you might notice gray, dark, or black smoke coming out from the tailpipe. The reason for this is that when your EGR valve is faulty, it restricts the airflow to the engine. At this point, your engine is running rich which means it is burning more fuel than air.

The reason for this can be either a faulty EGR valve or just a clogged EGR valve. Before you replace your EGR valve, you should always try to clean the EGR without removing it.

9. Engine misfire

What Are The 9 Symptoms of a Faulty EGR Valve

If your EGR valve is faulty, it can cause an engine misfire. There are two ways to diagnose this issue. The first one is to scan your vehicle with an OBD scanner and look for a P0300 – random misfire error code. The second one is to physically check the EGR valve and see if the gasket is broken or cracked. A simple crack can cause a vacuum leak.

The carbon deposits that accumulate in the valve will cause the valve to stay off of the seat and that will give the random misfire at an idle and create a drivability concern. If you check the EGR physically and notice some cracks, the replacement is in order.

I really hope you liked our article. My 2007 Hyundai had this issue and to be honest, I just didn’t care to diagnose it myself. That’s why I paid some mechanic to replace an EGR valve that could have been fixed with a simple cleaning. Always do some research before you throw your hard-earned money. Share your thoughts and experiences in the comment section.

Igor Iwanowski

I am a certified Automotive Service Excellence (ASE) mechanic since 2018. I specialize in Brake systems, dashboard warning lights, EGRs, general engine problems, EVAP and Emissions issues.

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