Why Does My Car Smell Like Rotten Eggs?

Why does my car smell like rotten eggs? Is the smell dangerous or requires immediate attention? These questions pass through everyone’s mind who’s suffering from stinky cars. But you don’t have to worry about it because every question is answered in this article.

Before getting into detail about the mechanical causes, you should look into the more obvious options. Thus, rule these things out and then diagnose other options further.

1. Smoking

Many car owners like to smoke and accumulate the remaining cigarettes in the ashtray. They get used to the smell, but new passengers often get uncomfortable with it and find it rotten and pungent. To get rid of that, clean the car thoroughly and use air spray.

2. Forgotten Food

Takeaways in cars are the best option to eat your favorite food with peace and privacy. But it can cause a rotten egg smell if forgotten for a long time. Mostly, our delivery bags contain small bites of food that produce bacterial growth and develop a bad smell in the car.

3. Dead Animal

This does not happen to everyone, but it does happen. Animals can get stuck in your car, under the seat, or in unusual places. So, they die and spread the rotten egg aroma all over the car. You have to inspect and remove the animal thoroughly as soon as possible.

Once all the above options are ruled out, start diagnosing, keeping the mechanical causes in mind. A few of the below are the most common causes of egg-like smells.

4. Air Conditioning Mold

Some people may notice a pungent or gas smell while starting the air conditioner, but it dissipates quickly. This is most likely due to the AC’s clogged air filters or bacterial growth.

The car smells like rotten eggs when the AC is turned on due to intense weather and a lack of proper cleaning. Bacteria accumulate in the vault and cause the egg to smell rotten.

You must repair, replace, or clean the air vents, air filters, or other AC equipment to fix this. But don’t ignore the issue, as it will worsen with time.

5. Leaky Transmission

If your car smells like rotten eggs when starting, it can happen due to a leaky transmission. This aroma is associated with Sulphur. Thus, old manual cars contain sulfur-based lubricants that can leak and drip on the hot engine. If you notice any dripping or leaking on the ground, check that immediately because it also indicates faulty gears.

If you are a pro at fixing cars, troubleshoot and fix the problem yourself. But repairing manual cars is a bit more tricky.

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6. Faulty Car Battery

Your car batteries also contain sulfur-based gasses and lubricants. They are inside the battery, but if it’s over or under-charged, it may leak and develop a rotten egg smell.

The fix is easy, yet a bit tricky. Before changing the battery, ensure your car has not overcharged because it will do the same to the next battery. Also, in case of a leak, do not jump-start the car. It can cause an explosion, too.

You can change the battery by covering your eyes and hands for prevention. But if you don’t want to get in a risky zone, contact the mechanic and get it changed.

7. Catalytic Converter

The catalytic converter is one of the most common causes of rotten egg smell. It can get clogged or broken, too. Most common problems are related to these three reasons:

  • Sulfuric Gas: A failing converter may not efficiently break down toxic chemicals or gasses. Thus, they produce sulfuric gas as a buy product that emits from the converter and spreads around with a rotten smell.
  • Catalyst Breakdown: Over time, the converter’s catalyst can degrade due to factors like fuel additives, oil contamination, or general wear. Thus, they emit a pungent rotten smell.
  • Fuel Combustion: Problems in the fuel combustion process, such as an imbalanced air-fuel mixture or a malfunctioning fuel injector, can lead to an increased presence of sulfur compounds in the exhaust, intensifying the rotten egg odor.

You can troubleshoot the converter, change its clogged components, or clean them thoroughly to eliminate the smell.

8. Exhaust System

Some exhaust pipes can get blocked with plastic covers or other materials. Thus, their heat burns the material, resulting in a rotten smell. This is mostly noticeable while driving.

The aroma stops when you stop the car as the plastic cools down. You can get rid of the smell by cleaning the surface and removing any material from the exhaust pipe.

9. Fuel Filter

A worn-out fuel filter also helps in building the rotten or pungent smell. I produce over-rich fuel that further affects the catalytic converter and leaks sulfur gas.

Thus, the converter can also burn out and get damaged as a byproduct. You should check the issue as soon as possible, as it will cause more damage in the long term.

car ac closeup for why does my car smell like rotten eggs guide.


How To Get Rid Of Egg Smell In Car

If your car smells and stinks, it can cause headaches and irritation or make your drive as uncomfortable as possible. To get rid of that aroma, you can use the following methods:

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Open the window

The most common is to open the window to increase the ventilation inside and eliminate the pungent smell. If the smell is caused by smoking, remaining food, or animals, then it is a highly effective way.

Find a dry spot with shade and breeze, park the car, and let your car breathe. You can open all the windows or even the door for some time to get rid of the stale air.

Activated Carbon

This removes the smell, absorbs formaldehyde, and freshens the air. So, place activated charcoal on the bamboo and set it in the car. The only drawback is its range is quite low, so you have to place it in several places to eliminate the pungent smell.

Use Fruit

Citrus fruits such as pineapple and orange effectively spread a fresh and fruity scent that diminishes the rotten one. Put them in front of the air conditioner or use their peels as a fresher. But make sure to change the peels regularly as they can rot and develop bacteria, too.

Car Purifier

An air purifier is a common method to deodorize the car and spread some good and fresh scent everywhere. You can choose your likable scent and place it in the car. This will be the most effective in overcoming the pungent smell.

Professional Cleaners

Contact professional cleaners to clean out air conditioner filters or catalytic converters to eliminate the rotten smell. They also do the job thoroughly and can check other underlying causes of the sulfur-based aroma.

DIY Cleaning

You can also try the things below to get rid of the smell:

  • Clean and wash every fabric, carpet, or seat with a baking soda and lemon mixture.
  • Dry out the product in the sun and let your car breathe in a cool, dry, sunny place.
  • Store a bag of ground coffee under the seat.
  • Store a bag of fabric softener in your car to eliminate the bad odor.
  • Get small bags of mint or vanilla extract and use them as a freshener to get back the new car scent.


What Are the Other Car Smells To Notice?

Just as the smell of rotten eggs can indicate different reasons or a cry for maintenance, other odors can also indicate different engine or car equipment failures. Here is what you should look out for:

1. Rubber

Worn-down belts or loose hoses are the primary culprits for burning rubber scents. It indicates a loose plastic thing in the car now latching to the engine. Get it checked before it can cause further damage.

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2. Syrup

A leak in the radiator can produce a sweet syrup scent in the car. You might notice it while accelerating or when the car is turning off. You have to check that promptly, as it can damage the engine further.

3. Musty Scent

If the scent is mild with unpleasant notes, it mostly indicates your AC’s growing bacteria or mold.

4. Gasoline

A lingering gasoline smell often indicates a fuel system leak or a broken vent hose. This can require immediate inspection.


The Bottom Line

The rotten egg smell in a car can be persistent due to various mechanical reasons. It is developed by sulfur-based substances usually emitted by loose or broken components. You can get rid of them easily if the issue is not serious. Although the smell is not dangerous depending on the cause, it can leave you stranded nowhere, too. So, check with a mechanic in a timely to fix the issue.


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