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What Causes a Rotten Egg Smell in Cars? Three Possible Culprits  

Rotten Egg Smell in Cars

A rotten egg smell in cars usually comes from a substance including sulfuric products. In most cases, to get rid of this bad smell, you must perform parts replacements.

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As a rule of thumb, if you smell anything weird in your car, you must not ignore it. Your car must not smell or make weird sounds. If that's the case, there is something wrong going on in your vehicle's internal components.

While some of this bad smell might come from a small issue, others might be very complicated and cause significant parts failure.

Whatever was the reason for this rotten egg smell in cars, you must act immediately and have your vehicle inspected and repaired by a professional mechanic. In some cases, you might need to give your mechanic a call before moving your vehicle to prevent causing more complicated issues.

The purpose of this article is to help you understand the different causes of rotten egg smell in cars. We also help you with additional information that you need to familiarize yourself with when you experienced this smell. Some of this information is related to repair costs and other experts recommendations

How can your vehicle generate sulfuric components? 


Rotten egg smell in cars usually comes from a component that has some sulfuric compound. This smell always indicates a significant problem in your vehicle's internal components. While you might not be happy with the smell, and it could bother you, you should be more concerned about what's going on inside the vehicle and have it repaired immediately.

The most sulfuric smell usually comes from fuel. In the exhaust system, hydrogen sulfide is usually transferred and converted into, and no compound is called sulfur dioxide. Sulfur dioxide does not have a smell and is considered safer to the environment than any other vehicle emissions. If you started smelling something like a rotten egg, something broke in the exhaust system, and the exhaust system cannot convert the compounds properly.

Usually, smelling something like a rotten egg happens when the engine does not completely burn the fuel properly. As a result, some of the unburnt fuel is leaving the exhaust system. 

What causes rotten egg smell in cars? 


Now we understand the theory behind how the rotten egg smell is generated in the car, and it's time to understand what would be happening in the car that is causing this smell.

In other words, what are the faulty parts that could result in a rotten egg smell in cars?

In most situations, three main culprits are resulting in rotten egg smell in cars, including: 

  • A problem with the catalytic converter 


If your car has some rotten egg smell, your first and most common reason is a broken catalytic converter.

The catalytic converter is a part attached to the exhaust system and is responsible for converting any harmful emissions into less harmful emissions to the environment.

As part of the catalytic converter's job, it's responsible for converting hydrogen sulfite into a new gas that does not have a smell that has caused sulfur dioxide.

If the catalytic converter goes bad over time of use, it's very likely for it not to do its job and not to be able to convert the hydrogen sulfide properly.

As a result, you will start smelling some rotten egg smell in the car.

Unfortunately, if the problem is coming from the catalytic converter, you must get the whole part replaced as soon as possible. 

  • An issue with the fuel filter or the fuel pressure sensor 


If you have confirmed that the catalytic converter is in good condition, your next bet should be related to the fuel filter or the fuel pressure sensor.

Your vehicle's fuel pressure sensor is responsible for maintaining the proper fuel flow to the different components of the combustion system. If the fuel pressure sensor is not working properly, it can introduce many oils to make its way to the catalytic converter.

An overwhelmed catalytic converter with oil cannot do its job properly. As a result, all the converter will not burn and convert harmful emissions into less harmful gases. Therefore, the hydrogen sulfite will leave the tailpipe and cause the rotten egg smell.

Like the faulty fuel pressure sensor, the fuel filter can also cause much dirt to make its way to the combustion system and introduce additional deposits on the catalytic converter. As a result, the catalytic converter can be jammed and will not do its job resulting in a rotten egg smell in your vehicle. 

  • A problem with old transmission fluid 


If you are driving a manual car, you need to maintain proper flushing to your transmission fluid. In case you missed the transmission fluid flush a couple of times, you will start dealing with some transmission fluid leaks into different components.

If the transmission fluid is leaking to other components, it is usually associated with a rotten egg smell.

Therefore, if you have a manual car, you need to follow the manufacturer's recommendations and flush the transmission fluid as needed. 

How to remove the rotten egg smell in cars?

To get rid of the rotten egg smell in your vehicle, you must identify the faulty culprit and replace it.

For example, if your mechanic said that the rotten egg smell is happening from a bad catalytic converter, you must get the catalytic converter replaced as soon as possible. The same goes for the fuel pressure regulator, the fuel filter, and the transmission fluid flushing. 

How much does it cost to remove rotten egg smelling cars? 


Like the previous question, the cost needed to remove rotten egg smells in cars depends on the faulty culprit.

For example, if you identified that the problem is happening due to a bad catalytic converter, you need to pay somewhere between $945.00 and 2475 dollars. This amount covers both heart and labor costs. If you are deciding to go to a small repair shop, the price can drop significantly.

On the other hand, and if you are lucky enough, if you knew that the rotten egg smell is coming from a bad fuel pressure regulator, you expect to pay somewhere between $252 and $336. Again, this price range includes both labor and parts costs. 

Lastly, if the problem is not because of a complicated issue and it's only just due to a bad fuel filter, you can replace it for somewhere between $53 and $16. 

Is it worth the repair to deal with rotten egg smell in cars? 


Well, answering this question depends heavily on the cause of this rotten egg smell.

For example, if the culprit is just a bad fuel filter, you can simply remove this filter and install a new one no matter what your vehicle's type is.

However, if your problem is related to the catalytic converter and you must install a new one, you need to step back and think thoroughly before making a final decision.

The catalytic converter is one of the most expensive repairs and could get as close as your vehicle's value.

Before making a final decision and deciding to replace the catalytic converter, you must ask yourself these couple of questions:

  • Does your car have other problems than the catalytic converter?
  • Are repair costs getting close to the value of the car?
  • Does your car have many mileages?

If your answer to any of the mentioned questions is yes, it might not be worth spending a penny on replacing the catalytic converter. 

But the question always remains, what should I do then?

Well, you are lucky enough because you are in the right place.

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Whether your car is dealing with problems with a catalytic converter or even a completely damaged vehicle, our company is willing to buy it.

Did you know that we pay the most cash for cars around your city? Yes! Our company is one of the top-rated car removal companies in the nation.

We have more than a decade of car buying around most cities in the United States.

Our process is very simple and straightforward, and all we need to do is give us a call and describe your car's situation.

Once you provide this information, our team will hand you an instant offer that reflects the top dollars your vehicle could ever make around your city.

If you're happy with the offer, we will connect you with one of our local car removal specialists, who will coordinate with you to select a pick up time and location.

Have a pickup time, and we will inspect your vehicle quickly and hand you the cash payment right on the spot! 


Can a rotten egg smell indicate a failing car battery? 


In some rare situations, your car's battery might start leaking a compound that has come so far in it.

If that's the case, your car's battery is failing, and you must get it replaced as soon as possible.

Usually, the rotten egg smell is not as strong as if the problem is happening due to the previously mentioned causes, including the catalytic converter, the fuel pump sensor, and the bad transmission fluid. 

How long can I drive with rotten egg smell in cars? 


Determining how long you can drive with this smell depends on the cause of the smell.

If your rotten egg smell comes from a bad catalytic converter, you can still drive the vehicle, but it's not recommended to drive for so long.

If the smell is coming from a clogged fuel filter, that fuel filter could cause significant problems and blocking the fuel from making its way to the combustion system completely. Even if replacing the fuel filter is not very costly, it can introduce significant problems to the engine, and you will start noticing some reduction in the overall engine's performance.

Similarly, the fuel pump sensor regulator can also affect the overall performance of the vehicle.

In general, when you smell a rotten egg, you will not stop driving. In other words, this snow should not stop the vehicle completely. However, you must take care of this problem to prevent dealing with complicated issues that could scarify your entire vehicle. 

Most automotive experts do not recommend ignoring any weird smell coming from your vehicle. Whether the smell is just a rotten egg smell or simply a gas smell comes from the exhaust system. These signs are just ways of your car trying to communicate with you and watching, and you know that there is something wrong with the vehicle. Perhaps some of these smells might be associated with some warning signs on the dashboard, while others will only be smells.

Never ignore how it will snow and have your vehicle inspected by your professional mechanic immediately. 



In general, your vehicle should not make weird noises or have strange smells. If you started to smell anything strange, the problem could be very serious, and you must get your vehicle diagnosed and inspected by a professional mechanic. Once the professional mechanic identifies the culprit, you must get it repaired as soon as possible.

Ignoring any bad smell like a rotten egg can cost you too much money and result in complete parts failure.

It is very common to deal with situations where rotten egg smell in cars. If that's the case, your main culprit would be about catalytic converter, a faulty fuel filter or fuel pressure sensor, or old transmission fluid.

Whatever the culprit was, you must get your vehicle repaired as soon as possible. When there is a rotten egg smell in cars, it will not prevent you from driving your vehicle, and that's where it's going to be your own wise decision about not driving it for so long and have it inspected immediately. 

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