Skip the auto shop - Our mechanics make house calls

Why Do Some Cars Have Really Smelly Exhaust Fumes?

gas fumes
Paolo Bona / Shutterstock.com

Most cars have minimal odor to their exhaust. It smells like, well, exhaust, but it’s not terribly strong. This is thanks in large part to the catalytic converter. However, some cars seem to have really smelly exhaust fumes due to a number of different reasons (depending on the smell in question).

Burning oil

If an engine is burning oil (due to leaking seals), then you’ll definitely notice the car has really smelly exhaust fumes. You may also notice that it creates smoke from the tailpipe (bluish in color).

Failing catalytic converter

Ever been riding along and suddenly smell rotten eggs? If so, you’re behind (or beside) a car with a failing or failed catalytic converter. Sulfur is found in gasoline, and is turned into hydrogen sulfide in the combustion process. However, the catalytic converter changes it into sulfur dioxide. This has no odor at all. As the cat fails, it stops changing hydrogen sulfide into its odorless counterpart and the result is a strong smell of rotten eggs from the exhaust.

Burnt antifreeze (hot and sweet)

If what you’re smelling is sort of “hot and sweet,” it’s probably engine coolant. There are many ways this can happen. A pinhole leak in a coolant hose can spray antifreeze onto a hot engine component, which boils the coolant away and creates that smell. It can also contaminate oil and be burned in the engine that way.

It’s a diesel

Diesel exhaust smells much stronger than the exhaust from a gasoline engine. You’ll also notice that the exhaust is darker, particularly on large trucks with powerful diesel engines.

Gasoline

If the exhaust smells like gasoline, it’s a sign that the air/fuel mixture is off in the engine and too much fuel is being added to too little oxygen.

If you notice any of these smells coming from your exhaust, you should have the problem diagnosed as soon as possible. If you notice there’s a strong smell of exhaust in the cabin, you should also have this diagnosed and repaired quickly. It’s a sign that your exhaust system is damaged. Keep the windows down to prevent carbon monoxide from building up in the cabin.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

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

More related articles

How to Get a Louisiana Driver's Permit
s licensing program. The first step in this program is to obtain...
Veteran and Military Driver Laws and Benefits in Idaho
The state of Idaho offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch in the...
P2159 OBD-II Trouble Code: Vehicle Speed Sensor B Range/Performance
Diagnostic Trouble Code (DTC): P2159 P2159 code definition Vehicle Speed Sensor B Range/Performance...


Related questions

Q: White smoke coming from tailpipe with the code for evap large leak.

Hi there. The white smoke coming from the exhaust system indicates that there is water (coolant) in the exhaust system. This is caused by the coolant getting into the combustion chamber and burning off with the fuel. The coolant is...

Q: Every three months, catalytic converter and muffler must be replaced

I would start with checking the O2 sensor. This is what relays exhaust gas changes to the vehicle's computer. When this sensor is not working correctly, incorrect or misdiagnosed air/fuel mixtures are relayed to the vehicle's computer causing incorrect changes...

Q: Car sounding weird after engine fire

I wouldn't recommend driving the vehicle until you have the car checked by a professional. Engine fires can be caused for many different reasons, and leave damage to several components of the car. With all of these issues, I would...