Does Your Car Smell Like Rotten Eggs? Here’s Why + How to Fix

I bet you’re a bit like me; you get irritated when your vehicle stinks. Have you ever had a situation where your car smells like rotten eggs?

On several occasions, I have been a victim of this. I had to follow my nose to get to the sources of the stench. Here are the most common reasons why it smells terrible and how to fix it!

1. Catalytic Converter Failure

If you smell rotten eggs in your car while it is running, there are a few possibilities. However, the most likely source is a failed catalytic converter.

This is where gases such as hydrogen sulfide are converted to harmless and odorless sulfur dioxide.

When this emission system malfunctions, hydrogen sulfide will not be converted to odorless sulfur dioxide. This means the vehicle will give out hydrogen sulfide that is characterized by the rotten egg smell.

Unfortunately, the fix here is to install a new catalytic converter. While it’s not fun to shell out the money to replace it, at least your car won’t stink anymore!

It’s also worth pointing out that it is dangerous to continue driving a vehicle with a broken catalytic converter. This is because it will cause the temperatures in the exhaust system to rise.

High temperatures are likely to cause your vehicle to catch fire.

Replacing the catalytic converter is the best way out of resolving this issue. On a few occasions, the catalytic converter may have been damaged by another component in the vehicle.

This should be checked thoroughly at the service shop to ensure the new catalytic converter is safe from damage.

2. Malfunctioning Fuel Pressure Sensor

The failure of the fuel pressure sensor can sometimes cause the catalytic converter to fail. The sensor is for controlling where the fuel goes in the system.

I have experienced several situations when the catalytic converter becomes blocked by excess oil if not properly regulated.

This would cause the emission system to malfunction. Therefore, the toxic gases will not be converted properly. And because of this, the vehicle will smell like rotten eggs!

3. Old Transmission Fluid

Old transmission fluid might also give off a rotten egg smell. To fix this, transmission fluid should be changed regularly, especially for a manual transmission car.

After a while, it can stagnate and leak into other sections of the vehicle, causing a bad smell in your car.

Before I go for a complete diagnosis of my engine’s emission system, I would first confirm I did not drop leftover food under the seats or in any hidden pockets in the vehicle.

If my vehicle still has the rotten egg stench after a thorough check inside the cabin, I head over for a check-up under the hood!

There is nothing worse than having an offensive or exceptionally pungent smell around you for long. Having a stench in your car, and worse still, the rotten egg sulfur smell can be frustrating.

If this happens, it is time to get your engine checked.

How to Fix Rotten Egg Smell in Your Car

If your car smells like rotten eggs, the best solution is to replace the defective element causing a problem. Whether it is the catalytic converter, fuel pressure sensor, or transmission fluid, you must deal with the malfunction immediately.

Once the parts are replaced, the rotten egg smell will go away. It is critical to be aware of any other likely source of the smell. Other things that can cause a pungent smell include; malfunctioning engine, leakages of fluids, or brake pads.

When this happens, you should consult a professional technician for help to diagnose and repair your vehicle. Driving your vehicle in this condition may cause further damage to other parts. Also, it is a danger to your health to drive with a cabin full of sulfur.

For the case of the fuel pressure sensor, it must be replaced to resolve the problem. This will also prevent the sulfur deposits from clogging the catalytic converter. If the sensor is working fine, the next component that must be checked is the fuel filter.

In the same way, a defective sensor may cause problems, a damaged filter can also cause clogging in the system. Hence the need for a complete replacement of the filter.

Frequently Asked Questions (FAQ)

What else can cause the cabin to smell bad?

Besides the smell of rotten eggs from sulfur emitted from the engine, you can also experience the smell of burning rubber or worn-out brake pads. This may sometimes be evident by smoke or a bad smell inside the cabin. This can be fixed by checking under the hood for loose belts and checking the brake pads soles.

Additionally, molds, fungi, bacteria, and other micro-organisms can also make your car produce a bad smell. Bacterial growth often occurs behind the evaporator’s dashboard panel. As a result, the air conditioner produces a foul smell.

What makes the air conditioner smell like rotten eggs when turned on?

This is commonly due to a faulty catalytic converter. This is the component responsible for converting the smelly hydrogen sulfide into harmless and non-smelly sulfur dioxide.

When this fails to happen because of a malfunction, the cabin is likely to smell when AC is switched on.

Other reasons behind this can be the accumulation of bacteria, fungi, or other micro-organisms on the AC vents. When they decompose after a prolonged period, they are likely to produce a smell similar to rotten eggs.

Will I see a light signal on the dashboard when the catalytic converter is faulty?

Yes. The catalytic converter is among the top causes for the “check engine” light to start flashing on the dash display panel. When this happens, it means that the converter should be replaced as soon as possible to avoid further damage to the engine.

It is recommended to have your catalytic converter checked during your routine vehicle checkup. This will help you to identify the faulty component before it fails completely and start producing a pungent smell.

Can I drive with a faulty catalytic converter? If yes, for how long?

It is not that dangerous to drive with a faulty catalytic converter. Your can will still drive well when a portion of the catalytic converter is connected. You will hardly notice the difference.

However, it is recommended to get the vehicle checked immediately you realize that the catalytic converter has a problem. Accumulation of sulfur in the cabin is harmful to the health of the occupants.

When the engine is burning too much oil or running for long, it can burn through the catalytic converter’s fiber. Driving your vehicle faster at this stage may lead to the production of smoke. The smoke will enter the cabin through the vents.

A clogged catalytic converter might cause the car’s engine to overheat, which can be disastrous. Refer to your owner’s manual for the recommended repair and replacement procedures for the catalytic converter. When your engine misfires, it is a sign of catalytic converter failure.

If you discover the sources of the rotten egg smell, you won’t have to perform any major cleaning on your car to remove it. The scent will go away once you have found and fixed the catalytic converter. Proper conversion of hydrogen sulfide to odorless sulfur dioxide will eliminate the smell.

Before heading to the technician to diagnose your vehicle, you should first ensure that the smell is not coming from rotten fruit or pieces of food in your vehicle. To do this, check your vehicle’s interior, especially under the seats.

If this fails, you can take your vehicle for a thorough check-up of the catalytic converter and transmission oil.

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Hi, I'm the founder of VehicleAnswers.com! Having owned a wide variety of vehicles in my life, I was astounded at how hard it can be to find answers to common automotive questions. Rather than sit idly, I decided to create this website to help others!