What Does It Mean If My Car Smells Like Rotten Eggs?


If there's a peculiar sulfuric smell in your car, you should get it seen to as soon as possible

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Like with strange sounds from your car, certain smells can also be an indication of a problem. If you've ever hopped into your car and caught a whiff of a strange rotten-egg-like smell, you likely have a problem that needs to be addressed quite urgently. Sulfur is most likely the odor you're smelling - a compound that is found in the gasoline that combustion-engined cars burn to run.

A car in good condition will have all the working parts to burn up the gasoline and convert the resulting emissions into a neutral gas that is then ejected from the car via the exhaust. It is quite the process, however, and if there is any sort of fault or damage anywhere in the system, the result could be ineffective emissions and the smell of rotting eggs in your car.

So, if you've wondered why your car smells like rotten eggs, read on to find out some possible causes for this kind of car trouble.

Rotten Egg Smell In Car BMW

Three Possible Causes of a Sulfuric Smell in Your Car

Whether you get the rotten egg smell in your car when accelerating or when it's just running, these are the three most likely causes as to why your car smells like rotten eggs:

  • Catalytic Converter: Your car's catalytic converter is designed to neutralize your car's engine's emissions, including carbon dioxide, hydrogen sulfide, and nitrogen oxide. A damaged or faulty catalytic converter will emit unfiltered and hazardous sulfur gas that can leak into the cabin. If your car's catalytic converter is clogged, it can overheat and will start burning the build-up of the byproducts clogging it, which will also result in hazardous gases being released into your car. You will notice the smell of sulfur in your car almost immediately after starting up the engine if the catalytic converter is the issue. Read more about catalytic converters and the exhaust system here.
  • Fuel Pressure Regulator: Responsible for regulating the flow of fuel in your car's engine, the fuel pressure regulator or sensor and fuel filter are other components that, if broken or faulty, will cause the catalytic converter to flood with oil and subsequently fail, emitting a rotten egg smell in your car. A mechanic will likely check the sensor and the fuel filter as well as the fuel pressure regulator in case this is the cause of the sulfuric smell.
  • Transmission Fluid: Your vehicle's transmission system requires plenty of lubrication to function optimally. If the system is damaged and leaking transmission fluid, this could also result in the smell of rotten eggs in your car.
Car Smells Like Rotten Eggs Mercedes-Benz
Catalytic Converter Smell BMW
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What To Do: Sulfuric Smell From Catalytic Converter Or Leaking Transmission Fluid

There are many small issues that you can deal with yourself on your vehicle and basic maintenance like oil changes and even changing out brake pads can be done at home with some guidance. Issues like the smell of rotten eggs in your car, however, are serious - the implication is that if you can smell it, noxious fumes could be leaking into the cabin.

The best course of action is to seek the help of a professional as soon as possible. Read our guide to finding a good mechanic here. Remember to drive with open windows for proper ventilation until you get there; it's not safe to spend time in an enclosed space with toxic fumes leaking into it.

Other Possible Odd Car Smells And Their Causes

Here are some of the other odors you could smell in your car and their possible causes:

  • Gasoline - If you can smell gasoline inside of your car time and time again and for long periods, it could be a sign that there's a leak in the fuel injection line or vent hose. You'll need a professional to diagnose and repair your vehicle, as this is a potentially dangerous fault, too.
  • Exhaust - The smell of exhaust fumes in your car is a sign of another potentially dangerous issue. It could mean that your car's window and door seals don't seal properly, or that there is a leak in your car's exhaust system.
  • Burning - There are several possibilities as to the smell of something burning in your car, including a burned-out electrical fuse, overheating AC compressor, and a loose rubber engine belt or hose. Never ignore a burning smell, though, and get it seen to as soon as possible.
  • Musty - If there's a musty smell coming through the vents, it's likely the car's air conditioner. It could be that a lot of moisture has accumulated in the air filter or drainage lines. This could lead to further damage to your car and to your health if ignored.
Sulfur Smell Car CarBuzz


Is the rotten egg smell in my car dangerous?

Yes! It is generally the burning of a toxic by-product such as carbon dioxide, hydrogen sulfide, and nitrogen oxide that results in the rotten egg smell, a symptom of a failure either in the fuel, exhaust, or transmission system. Breathing in toxic fumes is highly dangerous.

Will I have to purge my car of the bad smell?

No, oftentimes you'll just need to get a mechanic to repair or replace the car part that is causing the problem and the smell will dissipate; it shouldn't return once the issue has been solved.

Do hydrogen fuel cell vehicles have catalytic converters?

Cars like the Toyota Mirai, Honda Clarity Fuel Cell, and the Hyundai Nexo do not use traditional combustion engines and have no harmful emissions. As a result, hydrogen fuell cell vehicles do not need a catalytic converter the way gas-powered vehicles do. These kind of vehicles use precious metals as a catalyst for the chemical reaction needed to power the car, which is a catalytic converter of a different kind.

What is the problem if my car smells like rotten eggs and won’t start?

Whether it is a transmission fluid leak or issues with your car's exhaust or fuel system, if your car won't start, chances are there is a problem with the battery. If the battery has cracked, leaked some acid, or shorted out, you may catch the rotten-egg smell and have no power to start the car. A new battery is the way to go, here.

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