why does my car smell like rotten eggs
Vehicle maintenance

Why Does My Car Smell Like Rotten Eggs? Here’s How to Fix It

Driving a car is an engaging task that requires you to pay attention to different things simultaneously. You have to watch the road, listen to the sounds around you, and at the same time, be conscious of any unusual sound that may come from your car. Smells are one of the ways cars notify you when they develop a fault, and you have to know what each smell signifies.

In this article, we will answer car owners who are wondering “why does my car smell like rotten eggs” by telling you the causes and issues associated with the situation. We’ll also go over how to fix it! 

What Is the Rotten Eggs Smell in a Car?

When your car smells like rotten eggs, there is a small possibility that someone forgot a half-eaten meal. The greater chance is that something is wrong with your car and, particularly, the fuel system. This smell is unpleasant, but that is the least of your worries. Instead, you should worry about the functionality of your car and your health.

Causes of a Rotten Eggs Smell in a Car

If your car smells like rotten eggs, there are a few places you should look. First, the problem is often from the fuel system. It may be that the catalytic converter is faulty, the fuel filter is clogged, or the fuel pressure sensor is damaged. You should fix it early to prevent further damage to the car and your health. Read more below on why your car smells like rotten eggs.

Faulty Catalytic Converter

If you take your car to a mechanic and ask “why does my car smell like rotten eggs,” the first thing they will check is the catalytic converter. This part of the fuel emission device is also known as the “cat” and is responsible for ensuring that your car follows emission regulations. This is because fuel has some sulfur, which is dangerous to the human body.

The catalytic converter converts the hydrogen sulfide to odorless sulfur dioxide. The neutralized and harmless substance is then released into the environment. The problem is that when this catalytic converter stops working properly, the harmful sulfur is not converted, and it creates a rotten egg smell in the car. The smell comes from a build-up of the fuel by-products, which are overheated. The smell of sulfur is not normally dangerous, but too much of it can cause damaging effects.

why does my car smell like rotten eggs

Bad Fuel Pressure Sensor

After the catalytic converter, the fuel pressure sensor is the other common cause of a rotten egg smell in a car. This part regulates the flow of fuel within the car’s engine, dictating how much fuel should be pumped into the engine at a time. When the fuel pressure sensor starts malfunctioning, it leads to several other complications such as fuel leaks.

At first, it begins with the fuel pressure sensor flooding the catalytic converter with oil. This then degenerates into the infamous catalytic converter problem. It is only a matter of time before you start getting a rotten egg smell in your car. As soon as this happens, you need to get the car to the auto repair shop as soon as possible.

Faulty Fuel Filter

Apart from the fuel pressure sensor, the fuel filter is another likely cause of catalytic converter damage. The fuel filters are engineered to block dirt, debris, and other harmful substances from passing through the fuel into the engine. However, it is possible for the fuel filter to become clogged with dirt, which prevents it from working properly.

In such situations, the path of the fuel to the catalytic converter will be hindered, and this may cause the converter to malfunction. This chain of events results in the common rotten egg smell, and you have no option but to change the filter.

Transmission Fluid

Like every other automobile and electronic device, cars need to be serviced often. During routine maintenance, an automotive mechanic does random checks and updates such as changing the transmission fluid. The transmission fluid helps to lubricate the transmission system, including parts like gears.

However, if the transmission fluid stays too long in your car, it may result in a rotten egg smell coming from the dash vents. If this is the case, have a mechanic change the transmission fluid.

Car Battery

The rotten eggs smell that keeps coming from your car’s vents may be from the battery acid leaking. This is a really dangerous problem and should be attended to immediately. The leaking fluid from the battery causes the smell, but it may cause greater damage like the battery cell exploding or the battery getting ruptured.

A bad car battery can cause more problems than just an unpleasant smell. It is responsible for most of the electrical issues your car experiences. For these reasons, you should take your car to a qualified mechanic without delay once you notice any battery leakage.

Ways to Get Rid of a Rotten Egg Smell in a Car

After asking why your car smells like rotten eggs, the next step is to find solutions to the problem. You should get the car to an expert mechanic as soon as possible to prevent the situation from worsening. When you get to the technician, they may ask you some questions to detect what is wrong with your car. Once the technician knows the exact cause of the problem, they will fix it and return your car to normal.

Repair the Damaged Part

The major way to get rid of the rotten egg odor is to repair the damaged part of the car. Since the smell is caused by a part failing in its normal duties, fixing this part will eliminate the smell in no time. You will then, unfortunately, have to buy a new part to replace the damaged one, but the cost is definitely worth it. 

Whether it is the catalytic converter or fuel pressure sensor or filter, changing the part is all you need to do to make the issue go away. If your technician suspects the problem stemmed from the transmission fluid being too old, he will drain it and replace it. If the battery is the problem, it should be replaced entirely to prevent the acid from damaging other car parts.

Air the Car Interior

In most instances, the bad smell leaves once you fix the cause of the problem. However, you can still air your car’s interior to be doubly satisfied. You only have to open the car windows and go for a short drive. The air blowing in should take the smell out and leave your car smelling as fresh as possible.

Why You Should Remove the Rotten Egg Smell Early

You should not let your car smell like a rotten egg for too long. Even if you can tolerate the smell, it is not advisable. Tell any mechanic that your car smells like rotten eggs, and they will immediately tell you the possible dangers of the scenario. Below are some reasons you should get rid of the rotten eggs smell as soon as you notice it.

It Is Dangerous to Your Car

The major reasons your car might be smelling like rotten eggs are associated with the catalytic converter. As we stated earlier, the catalytic converter is responsible for turning the hydrogen sulfide in fuel into sulfur dioxide before releasing it into the environment. Therefore, if you do not repair the broken catalytic converter on time, it may increase the temperature of your exhaust system. This, in turn, can lead to a car fire.

It Prevents Greater Damage to Your Car

Fixing a broken part of your car, especially ones related to the fuel system, is cheaper than letting it grow worse. For example, it is usually cheaper to fix a broken catalytic converter or replace the fuel filter than to deal with the repercussions. The minor damage may lead to greater and more expensive damage in other parts of the car if you do not attend to it early. 

It Reduces Your Car’s Fuel Efficiency

A rotten eggs smell in cars often originates from a faulty fuel pressure sensor. The chain of events is such that a malfunctioning fuel pressure sensor often reduces your car’s fuel economy. When the catalytic converter becomes flooded with oil, it cannot process the emission process properly, which may lead to your car consuming more fuel than normal.

It Is Dangerous to Your Health

Using an air freshener will not rid your car of the rotten eggs smell. Even if you can repress the smell a little, it will not do you any good to neglect such a dangerous issue. The recurrent inhalation of the smell can depress your central nervous and respiratory systems. As a result, you may experience dizziness, difficult breathing, coma, and other symptoms.

This problem’s dangers to your health can be as mild as skin irritation or as significant as death. The latter is not common, but it is a possibility in the case of continuous exposure to the harmful smell.


You now know the answer to the question — “why does my car smell like rotten eggs?” If a rotten egg smell is present, you must ensure you take your car to the auto shop early to prevent complications for both the car and yourself.