3 Reasons Your Car Smells like Rotten Eggs

No one likes the lingering presence of an unpleasant or particularly potent smell. When driving, smelling a strong scent like that of sulfur — or “rotten eggs” — is often an indicator of a serious issue.

The smell comes from the small amount hydrogen sulfide, or sulfur, within the fuel. Hydrogen sulfide is usually converted into odorless sulfur dioxide. However, when something breaks within the vehicle’s fuel or exhaust system, it can inhibit this process and create the smell.

The byproducts and deposits causing the smell are left over from the incomplete combustion of gasoline being burned and can be traced to multiple system failures. Should the smell only occur briefly after using the engine at high revs, there is no serious issue to be concerned about. A lingering sulfur smell, however, needs to be investigated. Listed below are 3 reasons your car smells like sulfur.

1. Broken Catalytic Converter

The most likely culprit for a rotten egg smell, the catalytic converter is part of the vehicle’s emissions system. When gasoline reaches the catalytic converter, the converter transforms the trace amounts of hydrogen sulfide into the odorless sulfur dioxide. It is designed to reduce harmful emissions by “converting” exhaust gases, like hydrogen sulfide, into harmless gases. A broken or jammed catalytic converter cannot properly process the sulfur gases and will cause your car to smell like rotten eggs.

Should your catalytic converter be the cause of the smell, you need a new catalytic converter. If your converter is inspected and shows no signs of physical damage, another vehicle component has caused it to fail and needs repair.

2. Failing Fuel Pressure Sensor or Worn Out Fuel Filter

The fuel pressure sensor regulates the use of fuel in a vehicle. Should a fuel pressure regulator fail, it ends up clogging the catalytic converter with too much oil. Too much oil prevents the converter from processing all exhaust byproducts, which then exit the vehicle through the tailpipe and produce the rotten egg odor. An excessive amount of byproducts can also build up within the catalytic converter and cause it to overheat, also contributing to the smell.

In this case, a fuel pressure regulator problem can be fixed by replacing the regulator or fuel filter. A worn out fuel filter leads to the same problems caused by a bad fuel pressure sensor — an influx of sulfur deposits burned up in the catalytic converter.

3. Old Transmission Fluid

If you’ve missed one-too-many transmission flushes, the fluid may begin to leak into other systems and unleash a rotten egg smell. Typically only an occurrence in manual cars, changing transmission fluid as suggested by your car’s manufacturer can often solve the problem. Any leaks that appeared will need addressing as well.

Removing the Rotten Egg Smell

The best way to remove the smell of rotten eggs from your car is to replace the faulty part causing the smell. This could be a catalytic converter, fuel pressure regulator, fuel filter, or even old transmission fluid. Once the appropriate part gets replaced, the smell should disappear.

It’s important to take notice of all off or bad smells surrounding your vehicle. In addition to sulfuric odors, smoking or burning smells can indicate serious issues like an overheating engine, a fluid leak, or worn-out brake pads. Always seek the advice of an expert mechanic when it comes to diagnosing and repairing vehicle components.


Next Step

Schedule Check Evaporation Emission System

The most popular service booked by readers of this article is Check Evaporation Emission System. YourMechanic’s technicians bring the dealership to you by performing this job at your home or office 7-days a week between 7AM-9PM. We currently cover over 2,000 cities and have 100k+ 5-star reviews... LEARN MORE

SEE PRICING & SCHEDULING

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Recent Check Evaporation Emission System reviews

Excellent Rating

(4)

Rating Summary
3
1
0
0
0
3
1
0
0
0

Joseph

33 years of experience
540 reviews
Joseph
33 years of experience
Nissan Altima L4-2.5L - Car AC Repair - Carrollton, Texas
Very Enjoyable and helpful.
Mercury Cougar - Car is not starting - Garland, Texas
Arrived on time, very knowledgeable and friendly. Highly recommend Joseph!

Francisco

10 years of experience
174 reviews
Francisco
10 years of experience
Honda Civic L4-1.8L - Starter - Long Beach, California
Great job!
Chevrolet HHR - Car is overheating - Portland, Oregon
Good people's, quality service you will find with Francisco.

Neil

23 years of experience
7 reviews
Neil
23 years of experience
Honda Accord L4-2.3L - Check Evaporation Emission System - Greensboro, North Carolina
Neil was prompt and very helpful and honest with any questions that I had.

Christopher

25 years of experience
80 reviews
Christopher
25 years of experience
Dodge Grand Caravan V6-3.8L - Check Evaporation Emission System - Metairie, Louisiana
Personable, reassuring, a delight to work with

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

Related articles

How Far Can You Drive Your Vehicle on Empty?
Knowing how many miles you can drive on an empty gas tank prevents getting stranded. Nissan Altimas can go the farthest when the low fuel light is on.
How to Replace a Carburetor on Most Cars
A carburetor replacement involves the air cleaner, vacuum hose, car fuel line, and a number of other parts. This complex procedure varies by vehicle.
How to Clean a Throttle Body
A throttle body needs cleaning when the engine idle is rough, the engine stumbles through acceleration, or the Check Engine Light comes on.

Related questions

Check Engine code for catalytic converter.
This can be because the catalytic converter is bad or the sensor is defective. A qualified mechanic would have to scan the vehicle and check for broken up or rattling converte (https://www.yourmechanic.com/services/catalytic-converter-replacement)r signifying its coming apart inside.
EGR P0404 code accelerating. 2005 Buick Terraza
For this code, there is a related technical service bulletin (https://www.yourmechanic.com/article/how-to-use-a-technical-service-bulletin-by-parker-hill) 06-06-04-003D (http://workshop-manuals.com/buick/terraza_awd/v6-3.5l_vin_l/powertrain_management/prom_programmable_read_only_memory/component_information/technical_service_bulletins/customer_interest/06-06-04-003d/) dated March 20,2007. The TSB calls for installing a new EGR kit consisting of a new valve, tube, and wire connector, and directions to reprogram the powertrain...
Car ran out of fuel put more in but still not starting what could it be
Hello, thank you for writing in. Several things may be happening. One would be that the fuel pump simply burned itself out trying to suck for gas. This is not uncommon in these situations. Secondly, you may have sucked up...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com