Car Smells Like Rotten Eggs (Here’s Why & What To Do)

Most of us have experienced the unpleasant smell of rotten eggs at one point or another. But when your nostrils get a whiff of this smell coming from your car, this may seem like cause for alarm. Fortunately, it is often a pretty simple explanation for why this happens. In most cases, a car that smells like rotten eggs is simply due to a problem with a clogged or bad catalytic converter.

But that is the most common cause, but it’s not the only culprit. So in this article, you’ll learn everything you need to know to figure out why your car smells like rotten eggs. Let’s get into it!

Why Does My Car Smells Like Rotten Eggs?

The most common reason your car smells like rotten eggs is due to a faulty catalytic converter that cannot neutralize the sulfur left in the exhaust after the combustion process. But it can also be caused by a defective fuel pressure sensor or oxygen sensor that floods your converter with fuel.

But while these are the most common reasons why your car smells like rotten eggs, there are a few other possible causes too, so to not leave any out, we made a more detailed list for you here.

1. Clogged Catalytic Converter

A catalytic converter is a device that is a part of your car’s emission system. It is used to convert the harmful pollutants in exhaust fumes into less harmful substances. One of these harmful emissions is hydrogen sulfide, which is a gas containing sulfur and is well known for having a strong odor of rotten eggs.

Under normal circumstances, and when the catalytic converter is working properly, it neutralizes the remaining sulfur found in the exhaust after the combustion, resulting in no smell.

But when it’s not working properly, this sulfur gas can instead escape and not only cause damage to the environment but also make your car smell like rotten eggs.

Although they effectively reduce emissions, catalytic converters can become damaged or clogged over time and may need to be replaced.

2. Faulty Fuel Pressure Sensor or Bad Oxygen Sensor

Another common cause of a car smelling like rotten eggs is a faulty fuel pressure sensor. This sensor is responsible for regulating the pressure and flow of the fuel within the engine. If it fails, it can cause the engine to run rich (too much fuel).

A bad oxygen sensor can lead to similar results as the optimal air-to-fuel mixture will be thrown off.

As a result, the excessive fuel can make its way to the catalytic converter, which over time causes the catalytic converter to become clogged.

There is a saying that a car that smells like rotten eggs is a sign of a car that is running rich.

However, even if the root of the problem is a bad fuel pressure- or oxygen sensor, chances are you’ll need to have your catalytic converter replaced too. The best way to confirm this is to take your car to a mechanic. They will be able to diagnose it for you.

3. Old Transmission Fluid

While this is not very common, old or dirty transmission fluid may be responsible for the smell if it starts seeping into places it shouldn’t be and onto hot engine parts where it burns. This problem is typically only occurring in manual cars. But nevertheless, it means the transmission fluid is coming from somewhere, and you should address the leak as soon as possible and replace any worn-out gaskets or seals.

The best way to prevent this is to ensure your transmission fluid is in good condition by regularly changing it according to the manufacturer’s recommendations.

How to Get Rid of Rotten Egg Smell In Car?

The only way to get rid of rotten egg smell in your car is to identify and replace the faulty part causing the smell. This could be the catalytic converter, fuel pressure sensor, oxygen sensor, or old transmission fluid. Once you have replaced the faulty part, the smell should disappear.

Here’s how to troubleshoot the cause:

A faulty fuel pressure sensor or oxygen sensor should trigger a check engine light in most cases and, therefore, also throw a trouble code. The same goes for a catalytic converter if it’s clogged enough.

So the first thing you’ll want to do is to look for any OBD (On-Board Diagnostics) codes. And for this you’ll need a scanning tool.

Most times, your local auto repair store, such as AutoZone, will read the codes for you for free. But if you prefer to do it yourself, you can purchase your own OBD scanner for a reasonable price.

These OBD scanners are great tools that will often reveal a lot about what is wrong with your vehicle and, in your case, the faulty part causing the smell. However, if there’s no check engine light or trouble codes, it doesn’t necessarily mean your car is fine, just that it gets harder to determine the cause.

So instead, you’ll want to look under your car for any visible damage on your catalytic converter, and while you are at it, also check for any signs of wetness that can indicate a transmission fluid leak.

Next, if nothing indicates damage or any oil leak, it’s still a good idea to try to find out when the transmission fluid was last changed and compare it to the recommendations in your car owner’s manual.

At last, if there are no trouble codes, the transmission fluid is fine and there are no leaks, the catalytic converter likely causes the problem. And once the catalytic converter is replaced, the smell should disappear.

However, it’s always best to take your car to a mechanic to have them diagnose the problem if you’re unsure. The catalytic converter is an expensive part you don’t want to replace unnecessarily.

Can I Still Drive My Car If It smells Like Rotten Eggs?

You can still drive your car if it smells like rotten eggs. However, you should have it diagnosed as soon as possible and replace any faulty parts. If the problem is caused by the catalytic converter, driving your car for too long without replacing it can cause further damage to your engine and can even catch fire.

If you notice your check engine light illuminates and smell rotten eggs, it’s recommended not to drive more than necessary.

And if the check engine light is flashing, you should immediately pull to the side and turn off your vehicle. A flashing or blinking check engine light usually means damage happens as you drive.

If that’s the case, have your car towed to a preferred auto repair shop for diagnosis.

How Do I Keep My Car From Smelling Like Rotten Eggs?

The best way to keep your car from smelling like rotten eggs is to do regular maintenance and follow the manufacturer’s recommendations. It’s also good to be observant if you notice any change in your car’s performance and take action if you do.

A clogged catalytic converter, a failing fuel pressure sensor, or a bad oxygen sensor can all cause symptoms such as check engine light, misfire, poor engine performance, lack of acceleration, and more.

Final Thoughts

While a bad smell from your car is never pleasant, at least now you know some of the most common causes of why it smells like rotten eggs. So now it’s up to you to figure out the cause. In most cases, the problem can be fixed relatively easily. However, if you’re ever unsure, it’s always best to take your car to a mechanic to have them take a look.

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Rickard Cefalk

Rickard is the owner of and a dedicated and avid do-it-yourselfer who has always enjoyed working on his own vehicles since childhood. He now devotes his time to sharing his expert knowledge of car maintenance and other car-related information through his website.

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