My project 86 xj has the all black interior and I'm trying to revive the carpet from questionably a decade of sitting while rodents and others have inhabited the space doing their business all over.

I typically will treat the entire carpet section with heavy amounts of purple power or simple green, then scrub brush in the harder affected areas and let it sit for a short while then power wash the entire carpet and let dry.
The carpet doesnt feel soo welcoming after the fact but its certainly clean and it does prolly a 7/10 on hard stains.

I'm curious of others successful methods but to also revitalize some life out of the carpet as well. Like a Carpet shampoo?

 

Pressure washer?

 

Remove it from the vehicle. That is the best way.

Vacuum it really really well. Get all the dirt and crud out that you possibly can.

Get a bucket and mix some decreasing dish soap, purple power, lemon scented ammonia, and a splash of laundry detergent. Use a bunch of each and fill with hot water and make foamy if you want.

Use a soft scrub brush and basically spread it all around to soak the carpet completely with the mixture. The soft bristle brush helps spread it around without wasting so much with it running through the carpet. Spraying it with a squirt bottle doesn't get it down in the fibers.

Then start scrubbing the hell out of it with a stiff brush. Dunk the brush and start scrubbing. If you run out of mixture make another batch. You can't use too much. Scrub scrub scrub.

If you want you can either do this multiple times or you can rinse the carpet and start again.

Drape it over a fence or so.ething and preaaure wash the hell out of it

Eta
Don't just blast it randomly with the water. Start at the highest point you can and go down. Don't wash the dirt back uphill.