Why Does My Car Smell Of Rotten Eggs? | TOC Automotive College

When a car experiences problems, its symptoms typically involve performance changes and unusual noises. But did you know that you can sometimes smell the problem instead? That’s precisely what happens when your car smell of rotten eggs.

Your car smells of rotten eggs because you’re inhaling hydrogen sulfide, a colourless gas. That gas can come from rotten eggs if you’ve left them in your vehicle. However, they can also result from a clogged catalytic converter, faulty fuel pressure regulator, and old transmission fluid that’s leaking in your engine compartment.

Whether you study in an automotive college or are an everyday driver, you’ll want to know what causes that smell and how to fix it. So read through this guide to get the answers you need!

Am I Really Smelling Rotten Eggs In My Car?

When you notice the smell of rotten eggs inside your car, there’s always a chance that it’s coming from eggs that have gone bad inside the vehicle. But, of course, that’s only possible if you’ve been transporting eggs in that car recently, and some of them broke open and spilt somewhere in the cabin.

However, the problem with the smell of rotten eggs in a car is that they can also come from malfunctioning components inside the vehicle. More specifically, the smell could come from the fuel or emissions systems, which harm you and your passengers.

You’re actually smelling the smell of hydrogen sulfide, a colourless gas. The reason most people assume it’s the smell of rotten eggs is that eggs also release hydrogen sulfide when they go bad.

So, if there are no real eggs in your car that have gone bad, the smell of rotten eggs means there’s a severe problem with your vehicle’s components. That’s why you must never ignore that smell.

Instead, you must troubleshoot the problem, find the source, and resolve it immediately.

Is The Smell Of Rotten Eggs In A Car Dangerous?

Yes, the smell of rotten eggs inside your car isn’t just unpleasant, but it’s also incredibly harmful. Unless you have rotting eggs in your vehicle, that smell comes from hydrogen sulfide produced by a malfunctioning component inside your car.

That’s dangerous because the malfunctioning components that produce that smell typically relate to the car’s fuel and emissions systems. When those are experiencing problems, your vehicle is no longer safe to drive as it could overheat or potentially catch on fire.

So, you must shut the vehicle off and tow it to your preferred workshop for further inspection and repairs.

What Causes The Rotten Egg Smell In A Car, And How Do You Fix It?

Now that you know more about the rotten egg smell inside your car, you can troubleshoot and resolve the problem with the correct solution.

Here are the reasons your car smells of rotten eggs and what you can do to fix it:

1. Actual Eggs

Firstly, you can’t ignore the possibility of rotten eggs inside your car. As you read earlier, accidents can happen when transporting eggs inside your vehicle, perhaps after returning home from the supermarket.

Eggs can crack and spill out onto your car’s flooring or upholstery. At that point, wiping it clean will not be enough as the eggs will absorb into the fabric and become rotten over an extended period.

Again, this is only a likely reason for the smell if you’ve recently had eggs inside the vehicle.

The solution: Solving this problem will require a lot of cleaning effort and patience. Firstly, you’ll want to roll down your car’s windows and maximise ventilation. That will get most of the rotten egg smell out of the vehicle.

However, you must then find the source of the egg spill and clean it thoroughly with a car upholstery cleaning product.

Alternatively, you can also get the car cleaned professionally. Professional cleaners and car detailers will have the equipment necessary to remove even the worst smells from a vehicle.

2. Catalytic Converter

Another likely source of the smell is your car’s exhaust or emissions system, particularly the catalytic converter. This component is responsible for converting the engine’s harmful exhaust gasses to less dangerous ones before they exit through your tailpipe.

When that component becomes faulty, it’ll fail to convert hydrogen sulfide to another odourless gas. As a result, the hydrogen sulfide gas (which smells like rotten eggs) will build up inside your vehicle.

That smell will find its way into your vehicle cabin, where you smell it when entering the vehicle.

The solution: Catalytic converters don’t fail often, but they cause plenty of problems when they do. In this case, the rotten egg smell is just one minor symptom of the problem. The converter will also cause issues with your engine’s performance and emissions.

So, the only practical solution is to replace your catalytic converter with a new one.

Photo from Universal Technical Institute

3. Fuel Pressure Sensor Or Regulator

Above, you read that the failing catalytic converter could cause a rotten egg smell. While that’s true, the fuel pressure regulator could be the root cause.

When that regulator doesn’t function correctly, it’ll create a chain reaction that leads to the rotten egg smell inside your car. More specifically, it causes a chain reaction that clogs the catalytic converter.

And as you saw earlier, a catalytic converter that doesn’t work will fail to convert hydrogen sulfide, leading to the buildup of a rotten egg smell inside the cabin.

The solution: A faulty fuel pressure sensor or regulator must be replaced if it doesn’t work correctly. When you perform the replacement, be sure to check the catalytic converter as well to see if it’s still usable.

Fuel-Pressure-Regulator-TOC Automotive — Photo by Car From Japan

4. Transmission Fluid

There’s also a chance that the rotten egg smell is coming from old transmission fluid.

As you might already know, transmission fluid is necessary to lubricate and maintain your transmission system from within. Unfortunately, like all the other fluids your vehicle uses, that fluid eventually becomes dirty.

Unfortunately, a transmission fluid leak paired with old transmission fluid will cause the rotten egg smell to occur. The problem is much worse when the fluid leaks directly onto other hot components in your engine compartment.

The solution: Solving this problem is more straightforward. Firstly, you must find and fix the leak in your transmission system. Then, you must drain the old transmission fluid and pour fresh fluid into the system.

Doing so won’t just eliminate the rotten egg smell, but it’ll also save your transmission system from problems caused by dirty fluid.

You can learn more about troubleshooting cars and solving problems by pursuing an automotive education in an award-winning automotive college. The best place to do that is TOC Automotive College, the best automotive college in Malaysia.