Exhaust Smell Inside the Car: What to Do and What It Means

Smell at idle or in slow traffic, often with a ticking or hissing from under the hood

Likely causes

• Exhaust manifold gasket or manifold bolts leaking
• A crack in the exhaust pipe ahead of the catalytic converter

What to check

1. Listen for a ticking or hissing near the engine that is loudest when cold.
2. Look for black soot streaks around the manifold joints and pipe connections.
3. Have a shop inspect the exhaust from the engine back, since a leak near the engine is the one most likely to reach the cabin.

Smell mainly when accelerating hard, or with the rear window or tailgate open

Likely causes

• Exhaust being pulled into the cabin through rear body seals or unused openings
• Missing rubber plugs in the floor or rear panels
• Driving with the tailgate or rear window open, which draws exhaust inside

What to check

1. Close the tailgate and rear windows and see if the smell changes.
2. Inspect the rear seals and floor plugs for gaps or missing pieces.
3. Have the exhaust checked at the same time, since a leak is what makes this worse.

A rotten-egg or sulfur smell

Likely causes

• Catalytic converter working harder because the engine is running rich
• A failing catalytic converter
• Fuel mixture problems that overload the converter

What to check

1. Read the stored codes. A converter efficiency code or a fuel mixture code points the right way.
2. Look at the code's own guide before replacing an expensive converter.

Smells more like raw gasoline than exhaust

Likely causes

• Loose or damaged gas cap
• Evaporative emission system leak
• A fuel line or injector leak

What to check

1. Check the gas cap seal and tighten it until it clicks.
2. If you can smell fuel inside the car or see a leak, do not drive it. Raw fuel is a fire risk, so have it towed.

Related guides

• P0420: Catalyst System Efficiency Below Threshold (Bank 1)
• P0455: Evaporative Emission System Large Leak Detected