[TPAMB]

The way to get rid of that odor is to strike the entire interior of the car. As a detailer, I can tell you that you need to shampoo every inch of the car especially the upholstery and carpet. If you have a vacuum, buy car shampoo. Spray on upholstery. Let it sit. Brush it gently. Wipe it with clean microfiber cloth. Vacuum it to remove the moisture. That will do it. Repeat if necessary. This is essentially a alternative to a extraction but not everybody has a extractor. Get underneath the seats. Buy degreaser and dilute it well. Clean the surface area all around with the degreaser and a microfiber cloth.

Good advise. Don't forget the headliner. If the carpet still stinks, replace it with a new one. A lot of work but the results are remarkable.

 

[TPAMB]

I've heard people talk about an ass smell. Is it more joking or is there literally an ass smell that develops in some peoples car?

Yeah. People who don't throughly wipe and wear thin clothing. It's called a shit stain.