Ive noticed lately that when im stopped at red lights or parked with the car still running, my car starts to smell bad. Almost like a rotten egg type smell. If i park and turn my car off, you can smell it from the rear of my car, like its coming from the exhaust. What could it be? a bad cat?

I live in Alberta and its currently anywhere from 0 to -20 degrees celsius. Does the cold have anything to do with it?

thanks!

bad cats replace them with test pipes!

Check for exhaust leaks from the Cats and Exhaust

How does it sound?

It sounds alright i guess. But it does kinda seem quieter then it should be. And when i shut my car off something rattles for a quick second and then thats it

I have no idea but i am here to learn about this. Did you check for leaks yet? If it is the cats, this could be a great time for upgrades.