I found a "recipe" for carpet cleaner: "Carpet stain removal:
A mixture of 1 teaspoon of liquid detergent and 1 teaspoon of white distilled vinegar in a pint of lukewarm water will remove non-oily stains from carpets. Apply it to the stain with a soft brush or towel and rub gently. Rinse with a towel moistened with clean water and blot dry. Repeat this procedure until the stain is gone. Then dry quickly, using a fan or hair dryer. This should be done as soon as the stain is discover"
My cat threw up in the basement and, even though I cleaned it up using some carpet cleaner soap stuff, it didn't come all the way out. So I gave this a whril, and it came right out! I tried it on another stain, which I think was actually paint, and even that came up (pictured with before and after)! I'm not sure how much of it was the vinegar and how much of it was the detergeant, but either way, it worked to clean my carpet!!