I read on the internet to use 50% water and 50% white vinegar (first step) and then baking soda (second step) and the final step is hydrogen peroxide and liquid soap to rid carpet of pet urine ammonia smells. It did not work. The house smells even worse. I need to know what I can use to neutralize the ammonia smell in the carpet.

Is it cat or dog urine?

If it's cat. I hate to tell you this, but after going through this buy using every method out there - even those that claim it will work, I never had luck. I ripped the bloody carpet out, made sure the sub floor underneath was sealed and put in new flooring.

Adding more items to the mix is going to drive you crazy. I had others try too, and eventually they gave up as well. Maybe someone here can make suggestions, but being the determined type myself - you may have to resolve yourself to just replace it and seal that floor underneath! Some of those who I know just kept using the white vinegar method several time and did have some luck, but eventually - they teared out the carpet.

The important part here that should never be dismissed is sealing the subfloor before replacing the flooring.

By the way - I don't suggest using liquid soap on your carpet.

I found this: Getting urine smell out - Cleaning Tips Forum - GardenWeb

If it's not too saturated in the carpet, then I suggest using this spray called "Dumb cat" it's expensive, but it worked for my carpet. You just need to saturate the spot completely with the stuff, it lifts out the odor and repels the cat. Good luck.

Bicarbonate Soda works really well for odour and moisture.

We just sprinkle some over the area, let it soak up any left over moisture and then vacuum it up.

When my parents laid new carpet they sprinkled some under the new floor covering to help keep any smell away ;)

You will have to use a product that has enzymes that "eat" the odor and stain.
Walmart.com: Out!: Stain & Odor Remover, 32 fl oz: Cats

The enzyme products do not work. I've used the following for both cat and dog urine:
Kids 'N' Pets
Febeze Pet Odor Eliminator
Renuzit Super Odor Neutralizer
If possible soak up wet urine. Let area dry. Then SATURATE the area with one of the above (use enough to make sure the pad and subfloor get saturated too). Let air dry. If necessary cover with a dry towel with heavy book on top to help soak up while drying. It may smell even worse while drying. Be sure to dry completely. Sometimes the area needs two treatments. After completely dry, use a good carpet cleaner product like Resolve (the aboe products will leave a residue on the carpet that will attract dirt). Spray on, let dry, then vacume.

Those products above contain enzymes which is what gets rid of the urine smell.

I should clarify, the enzyme only products, like Nature's Miracle, and the oxy-type products don't seem to work well on cat urine.

I have a dog and her pup. When this problem worsened, I washed it water and disinfectant and kept out in hot sun from 10 a.m. to 3 p.m. and practically 90% of smell was lost. Cheapest and easiest.

There is no miracle cure for removing pet/ammonia odor from carpet. Some carpets hold the smell worse than others but sad to say, they can put a guy in space but as for the feline urine and its post saturation smell, it really is eternal. Someone should really get to work on the chemical process to ameliorate this dilemma, and make themselves a zillion bucks.

Well, am in a pickel. I have had a lot of cats, 5 an d 4 dogs at once. When it comes to cats, the Urnine is impossible and I used the vinager/bakinsoda to the expensive treatment.. no luck.. ended up haivng to rip out the carpet and lay lanolium.
As for my dogs, I move into a rental and at the end of the hall or just hallway, I attempted to shampoo.. I mixed so many different agents that before I knew it I was calling the Poison Control Center and have been home from work to around a total of 10 days off and on from the horrible oder that I can't get rid of. I mixed everything in the book and the smell actually got worse and worse to a point I because very ill. I am now going to try the Soe 10x removal. I hope this works and if it has for anyone, would you share the outcome with me?? I really need some help because I am not going to remove the carpet as my dogs did make this mess, as it seems to be just seeping out with every plain water rinse and its like the carpet contains so many different chemicals if finally reacted.. Open for suggestions and no, moving isn't an option. Thank you.