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Why Does My Car Smell Like Rotten Eggs? How Do I Fix It?

  • Auto Insurance
  • Renee Martin
  • 8 minutes

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You start your car, and a rotten egg smell attacks your senses! No one, absolutely no one, enjoys this rank odor, but what causes it, and how can you fix it?

Few things are more frustrating than sensing something is wrong with your car. There are overt indicators like strange noises or motions and covert ones like a strange odor in or around your car. Drivers should never discount the power of smells. Potentially life-threatening car issues could be indicated by these strange car smells. Smelling sulfur or getting a rotten egg smell while behind the wheel is usually a sign of something more serious.

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Why does your car smell like rotten eggs?

This weird smell is caused by the hydrogen sulfide, or sulfur, in the gasoline. In most cases, hydrogen sulfide is transformed into odorless sulfur dioxide. But when something breaks within the vehicle’s fuel or exhaust system, it might obstruct this process and cause a rotten egg smell.

If the stench appears only briefly after using the engine at high revs, there is no cause for alarm. A prolonged sulfur odor, on the other hand, must be explored. The three main reasons why your car smells like sulfur are listed below.

Faulty catalytic converter

The catalytic converter, which is part of the vehicle’s emissions system, is the most likely source of a rotten egg odor. When gasoline enters the catalytic converter, trace amounts of hydrogen sulfide are converted into odorless sulfur dioxide. Its purpose is to reduce harmful emissions by “converting” exhaust gases such as hydrogen sulfide into innocuous gases.

Unfortunately, a clogged or malfunctioning catalytic converter cannot effectively handle sulfur gases, causing your vehicle to smell like rotten eggs.

If your catalytic converter is the source of the odor, you will need to replace it. If your converter is inspected and exhibits no symptoms of physical damage, it is likely that another vehicle component has failed and requires repair.

Fuel pressure sensor failure or worn fuel filter

The fuel pressure sensor controls a car’s fuel consumption. A clogged catalytic converter results from too much oil getting through a faulty fuel pressure regulator. If there’s an excess of oil in the system, the catalytic converter can’t break down all the waste products of the engine, and those gases leak out of the tailpipe along with the rotten egg smell.

Overheating of the catalytic converter, which is caused by a buildup of byproducts there, is another possible source of the odor.

Substituting a new fuel pressure regulator or fuel filter will solve this issue. Fuel system issues, such as increased sulfur deposits burnt in the catalytic converter, can be traced back to a worn-out fuel filter or a faulty fuel pressure sensor.

Transmission fluid issues

If you skip too many transmission flushes, the fluid may seep into other systems and emit a rotten egg odor. Typically only seen in manual transmission autos, replacing transmission fluid as recommended by the manufacturer will typically remedy the problem. However, you must also address leaks, if any.

Dead animal

We’ve only mentioned mechanical causes so far, but there are a few others to consider. For example, a dead animal, like a mouse or a rat, in your car’s engine compartment, exhaust system, climate control system, or interior happens more frequently than you might imagine.

Animals seek out warm places to sleep as the temperature drops, and engine compartments and exhaust systems are common choices. When you start your automobile, you risk killing them. If that happens, their bodies will begin to rot. As you might expect, this doesn’t have a pleasant smell. This could be the source of the foul odor that seems to accompany your automobile wherever it goes.

A rotten egg

If it smells like a rotten egg, sometimes, it just might be a rotten egg! The odds are much less, but groceries can fall out of bags and disappear behind the seats. It’s not unheard of for folks going through a messy breakup to hide a cracked egg in a secret compartment of their ex’s car.

If you ever get the unpleasant aroma of rotting eggs in your car, it could be due to a bad egg, milk, broccoli, or other food items you forgot to throw out.

Is it safe to drive a car that smells like rotten eggs?

The rotten eggs smell usually indicates that something sulfurous isn’t working properly. That can be harmful. So you shouldn’t drive a car that smells like rotten eggs.

It’s easy to assume that if the rotten egg smell comes from an emissions part, you may keep driving for a long time without dealing with it. Although this may be the case for most vehicles, we strongly advise against doing so.

Overheating can occur if the catalytic converter is blocked, and it can catch fire if it gets hot enough. Of course, this is the worst-case situation, but it should remind you not to disregard a rotten egg odor in your vehicle.

What you should do when your car smells like rotten eggs

If your car smells like rotten eggs, and you can’t figure out why it’s best to book an appointment with a reliable mechanic as soon as possible. A mechanic or auto shop has the equipment to determine the source of the smell. They can also solve the underlying problem with your car.

Having your car checked by a professional mechanic will help narrow down the source of the unpleasant odor. For instance, the catalytic converter may need fixing or replacing. Only a professional can do that properly.

If you notice a problem with your fuel pressure sensor or fuel filter, get it checked out. Doing this as soon as possible saves you time and money. Establishing a regular maintenance plan is good if this is your first visit to the mechanic. If you take your car in for routine service at regular intervals, the mechanics there may be able to spot problems like these before they become a major hassle for you and your vehicle.

DIY tips if your car smells like rotten eggs

If you want to try and figure out what’s going on yourself, these instructions will help you understand what’s happening:

Scan for trouble codes

There’s a good chance that your car has a “check engine” light on as well, and the first thing you should do is find out what that code means.

To do this, you can either buy a good scan tool for your car or take it to a local auto parts store, where they’ll read the code for free. Even if the check engine light isn’t on, you should do this to make sure there isn’t a code and the check engine light isn’t broken.

Check transmission fluid levels

You should then compare the period since you changed the transmission fluid with the recommended service interval for your vehicle. Transmission fluid can be the source of the odor if there is a significant disparity.

If you notice that you’re running low on fluid, you’ll have to inspect a wide variety of parts to pinpoint the source of the leak, rectify the leak, and then replace the fluid.

Ensure the fuel pressure sensor is working

You should then use an automobile scan tool to check the fuel pressure sensor’s output specifications, which is the next recommended test. Sensor failure without an accompanying engine code is also unusual.

After making these checks, it’s reasonable to assume that a broken catalytic converter is the source of the odor. Switching out the converter should do the trick to get rid of that odor.

Go through your car thoroughly

If there is no code and the transmission fluid is not outdated, you will need to begin investigating the car. It is a little strange that there is no check engine light on, but the catalytic converter could fail. Do yourself a favor and search the entire place to ensure that no food, tricks, or dead animals have been hidden.

Will the smell go away on its own?

Having a car that smells like rotten eggs is something that is not going to go away on its own. The problem will only worsen if you don’t take any action to fix it.

The problem will only get worse until you resolve the underlying reason, whether it’s forgotten food or a broken converter.

We suggest getting an estimate and fixing the problem as soon as possible by taking your car to a professional if you cannot do so yourself.

Auto insurance is the first step to good car care!

Visiting a professional auto mechanic regularly is essential to keeping your vehicle in great form, but unforeseen repairs can add up quickly. Reviewing your auto insurance policy to ensure you’re not overpaying for your car’s coverage is the best place to start if you’re looking to save money for unexpected car repairs.

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