Why Do Some Cars Have Really Smelly Exhaust Fumes?

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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.


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Rigoberto

9 years of experience
706 reviews
Rigoberto
9 years of experience
Hyundai Santa Fe - Exhaust fume odor in car - Glenview, Illinois
Rigoberto was communicative, punctual, and considerate of my time. He quickly and thoroughly assessed the problem and explained it well to me.
Chevrolet Traverse - Exhaust fume odor in car - Lombard, Illinois
knew what he was talking about

Mazyar

6 years of experience
97 reviews
Mazyar
6 years of experience
Mazda 3 - Exhaust fume odor in car Inspection - Decatur, Georgia
On time, friendly, thorough

Charles

24 years of experience
134 reviews
Charles
24 years of experience
Nissan Rogue - Exhaust fume odor in car Inspection - Renton, Washington
Excellent service. He inspected my car very thoroughly and drove the car with me to find the exact issue. Very pleased with his service.

Chris

20 years of experience
1612 reviews
Chris
20 years of experience
Nissan Pathfinder - Exhaust fume odor in car Inspection - Temecula, California
He was early and took the time to cover everything with me. He was great

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