Car Maintenance And Repairs

Why Does My Car Smell Like Rotten Eggs? What To Do?

Mike Cross
Updated Nov 28, 2021
Why Does Car Smell Like Rotten Eggs And What Can You Do About It

Oh no, your car has a bad smell coming from it. It smells like rotten eggs. Now you are wondering what that smell is coming from, and also even more importantly you are wondering how you can make it go away.

Well, in this article we will explain the reasons why your car smells like rotten eggs. After that, we will talk about what you can do about it. Read on to learn the most common reasons for a rotten egg smell in your vehicle.

Why Does Car Smell Like Rotten Eggs And What Can You Do About It
Why Does Car Smell Like Rotten Eggs?

What causes this rotten egg smell in car


So, before going into what could be wrong with your car, we will first explain what a rotten egg smell is. This is important to understand because it will help you know what parts of the car to check, and why these parts might be the thing causing the rotten egg smell.

So, when it comes to rotten eggs smells, what you are smelling is sulfur. This sulfur normally comes from leftovers in the combustion process. Knowing this can help get you on the right track of what parts of the vehicle you need to check.

1. Cracked Catalytic Converter

The first part that is the most common cause of rotten egg smell is a bad or damaged catalytic converter. The reason the catalytic converter is the main cause for rotten egg smell is that the job of the catalytic converter is to convert harmful emissions into ones that aren’t harmful. One of those harmful emissions that it is supposed to convert is sulfur. Sulfur happens naturally in our environment, but a lot of extra sulfur being put out is a bad thing. Also, it isn’t good for humans to breath sulfur as it can lead to headaches and other symptoms.

If the catalytic converter is cracked or damaged, then it can not do its job. If it is cracked or damaged, then the only thing you can do is replace it.

If you do an emissions test on your vehicle, then it can help you determine if the catalytic converter is not working. If it isn’t working, then you will need to check it. If it doesn’t show any visible damage, then it still might be the problem. That is because it might not be getting the proper power it needs to work.

To check that you will have to test the power supply. If that is okay, and the catalytic converter is okay, then the problem probably lies in another part of the system.

2. Fuel Management Sensor

Fuel Management Sensor can make car smell like eggs
Fuel Management Sensor can make car smell like eggs

One of the other parts of the exhaust system that might not be working is the fuel management sensor. The fuel management sensor is responsible for how much fuel and oil go into the engine for combustion. Too much oil in car car engine can lead to a couple of problems for the catalytic converter. One is that if it releases too much, then too much byproduct will be created. This will make it so the catalytic converter can’t process it all. The part of the gasses that aren't processed will build up in the catalytic converter and also build up in the tailpipe. This build-up will smell like rotten eggs.

Another way that a bad fuel management sensor can lead to rotten egg smell is that it can cause the catalytic converter to run hot. It might start running hot because it has too much gasses to process. Running hot is bad for multiple reasons. One this is more wear and tear not the converter that can lead to damage to it and cracking. Also, running hot can lead to the buildup burning off. This buildup burning off would create the rotten egg smell that you are smelling.

3. Sulfur Deposits

Sulfur deposits can also happen naturally over time in your vehicle. If it is an old vehicle, then this might be the case of the smell. You might need to have your fuel and exhaust system cleaned out.

If you notice the smell of rotten eggs when revving your engine, then this is a key sign that the smell is being caused for this reason. If the smell goes away after revving your engine at high revs, then everything is okay and you don’t have to worry. However, if the smell lingers, then this is an indicator to have the fuel management sensor checked.

4. Old Transmission Fluid

Transmission oil fill up in a car engine with metal cone.
Transmission oil fill up in a car engine with metal cone.

The last reason why your car might have a rotten egg smell doesn’t have to do with the engine or exhaust system at all. It has to do with the transmission.

If you have not changed your transmission fluid in a while, then sulfur can start to build up in it. If it goes too long, then you will be able to smell it. This is a lot more common in manual cars, but can still happen in automatics. Also, if you smell sulfur and you think it is the transmission, then it probably means you have a hole somewhere in the transmission.

That means you will need to change the fluids and have the transmission repaired. This can be costly, so it is important to start on top of the transmission fluid changes so the transmission stays lubricated, at the right temperatures, and doesn’t get damaged.

How do I get the egg smell out of my car?

So, now that you know the causes of the rotten egg smell in your vehicle, How do I get the egg smell out of my car?

Well, first you need to fix the problem that is causing it. Once you have done that most of the smell should go away. If it doesn’t, then you can vacuum the interior of the car and clean it well. When cleaning be sure to get the smallest gaps too because smells can hide anywhere. You can also use baking soda to help absorb any bad smells. Just pour some baking soda onto the interior of the car. Rub it in and let it sit for a while, then come back and vacuum it up. Baking soda is a great deodorizer.

You can also deodorize your car with other things. You can use natural substances, charcoal, and your typical air fresheners. Once you have the case of the rotten egg smell taken care of, deodorizing isn’t too hard. If your attempts don’t work though, then you can always take your vehicle to a professional detailer, and they can help you get your clean car smell back.


So, now you know the causes of rotten egg smell in your vehicle. You know that it is from sulfur buildup and that this can occur in the catalytic converter or transmission fluid. You also know why it happens in these places and what to do about it.

Lastly, you know how you can get the smell out of your vehicle once you have the cause of the rotten egg smell taken care of. Rotten egg smell and other smells in your vehicle is a good sign something isn’t working right, so it is important to take them seriously and find the problem for the sack of your car’s condition as well as your nose.

Mike Cross
Life is too short to drive with stock audio

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