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Q: Is there a smell which develops in a car when the catalytic converter starts to go bad?

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About one week ago, a strong unpleasant odor developed in my car. It just started one day; nothing I can think of was the cause. I had my local tire shop put the car up on their rack to inspect the underside chassis for maybe a small animal nest. Found nothing inside or out. A gas station attendant I use on a regular basis thought the smell (rotten eggs) might be the start of trouble with the catalytic converter. Any truth to that claim?

My car has 147500 miles.
My car has an automatic transmission.

Hi there. If there is a rotten egg or sulfur type of smell then most of the time this is caused by a failure in the catalytic converter. When these fail and become too hot they will smell like this. It needs to be tested with a temperature gun or with a back pressure tester. Both of these will help to identify this as the problem. A cylinder misfire will also cause this to occur. If you want to have this exhaust smell diagnosed, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose and repair this.

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