pooping on the carpet

Question
I have a 5 yr old Maltese that orgiginally was a puppy mill dog than went to a home where she was not made to go out and potty.  She had freedom to go wherever she wanted to.  I got her and we feel like we have rescued her but she will still poop on the carpet.  I was told that if I spray vinager on the carpet she will not poop on it.  I have cleaned the carpets numerous times and mainly she only does it at night or early morning.  I have bought diapers for her and hate to have that added expense.  Please let me know what to do....
Thank you

Answer
Put her in a crate at night and that will solve your night/early morning problem. As to during the day, it is about time someone housebroke this dog, although, since she has been allowed to potty at will for five years, she will probably never be reliable.

Keep her in the crate when she cannot be watched, at night, and when no one is home. Take her outside first thing in the morning, after she eats, every couple hours during the day, and last thing at night. PRAISE HER when she potties outside. If you think she needs to go and she doesn't, put her back in the crate and try her again in a half hour. Keep a journal of her potty times so you can see a pattern.