I recently bought this car. Is there a cabin air filter in a 2008 Grand Marquis?

 

I didnt know this myself but apparently there are three locations of where it could be, but its most likely that its going to be behind the glove box. You should spend some time looking through the car's manual.
However, I found a website that helps teach you how to change the cabin air filter and tells you where it might be located.
I hope this helps
p.s. I'm surprised that there's another person who drives the same year marquis as I do.
https://victoriamgclub.com/how-to-ch...grand-marquis/

 

Your 2008 G.M. does not have a cabin air filter.