housebreaking

You need a crate for each dog and they will whine and such till they learn that they get crated at night and when your not there.  You have to ignore the crying.  I would also keep them from having free roam of the entire house till they are housebroke, maybe keep them gated in a kitchen only.  If they start making messes in the house then only allow them out in those rooms on a leash, so you can take them out and they cannot sneak and eliminate in the house. 

Hi, you said that no matter what you do, they cannot be housebroken.  Can you tell us exactly what you do?  or have tried?  Maybe you just need a new method, or to adjust whatever you're already doing.   Do you take them out to potty on a strict schedule, or do they alert you when they  have to go?  How do you deal with accidents?  (do you get upset?)  Do you reward them when they do go outside?   When and how often do they have accidents?  

ORIGINAL: labcrab

Hi, you said that no matter what you do, they cannot be housebroken.  Can you tell us exactly what you do?  or have tried?  Maybe you just need a new method, or to adjust whatever you're already doing.   Do you take them out to potty on a strict schedule, or do they alert you when they  have to go?  How do you deal with accidents?  (do you get upset?)  Do you reward them when they do go outside?   When and how often do they have accidents?  

 
That's a very good question, I should have mentioned this, I just know nothing about "Birthin no puppies".
 
I take them out consistantly, when we get up, around five, approx every two hours.  I feed them at the same time, of course they always have water.
I only got upset once when I stepped in somethng that was rather warm. 
I clean up each accident, use vinegar, I've rented steam cleaners.  I tell them how good they are when they do their job out side (fenced in yard, still we take them on a leash).
When my son had them, they worked afternoons, I had the impression that, they didn't get to upset, or clean up each mess as needed, food at all times, junk food diet.  I'm trying to change all this.............But............

ORIGINAL: puppylove4u

That's a very good question, I should have mentioned this, I just know nothing about "Birthin no puppies".

I take them out consistantly, when we get up, around five, approx every two hours.  I feed them at the same time, of course they always have water.
I only got upset once when I stepped in somethng that was rather warm. 
I clean up each accident, use vinegar, I've rented steam cleaners.  I tell them how good they are when they do their job out side (fenced in yard, still we take them on a leash).
When my son had them, they worked afternoons, I had the impression that, they didn't get to upset, or clean up each mess as needed, food at all times, junk food diet.  I'm trying to change all this.............But............

 
A couple of things that come to mind that may help..    You need to use an enzymatic cleaner - one that will actually break down the protein in the urine/feces.  If you're just using vinegar, they can still smell the spots and may be intentionally marking in your house (females mark too!).  You could also use a black light, just to make sure that your cleaner is working.  Trust me, even if you smell nothing - they smell it.   I still use my black light when I'm cleaning the human bathroom!!! (ACK!)   The Petastic brand worked well for me, I used it in conjuction with one of those Bissel cleaners.  I found that the Bissel cleaner is what *really* did the trick.  
 
The other thing is, since they're a bit older (for potty training) - you really need to make a BIG impression  because all this time, they've been thinking that they've got it right!   So, don't just say "good dog" when they DO go outside - throw a party!!!  Shock them with your excitement over going outside.   Give them their absolute fav treat - (like a stinky hot dog bit, or some roast beef).  You could also try using a Clicker at your potty party.  This will help to really drive it home for them and mark this as an actual desired behaviour as opposed to "business as usual".  
 
Also, when are they having accidents?  You may need to resort to crating them at night just long enough for them to "get it".  Honestly, you're going to have to do Potty Training 101 here. 
 
Oh, do they alert you in any way when they have to go?  What lots of people do (myself included) is use a bell.  It just hangs over your doorknob and you teach them to touch it with their nose when they have to go.  It sounds kind of crazy and hard to teach, but it's surprisingly easy.  Slick pretty much taught himself to use it and it's a BIG help in avoiding accidents.

Hi, chiwuawua's have very small bladders, so it's not unusual that they cannot hold it in as long as other dogs.  I don't usually advocate this, but it might be worth a shot to try using a puppy training pad.  Just place the pad in a designated area such as a bathroom and with some help your dogs should learn to use the pads.  One thing that might help is to soak up their pee with a paper towel and place them on the pad.

I've also heard of people who trained their small dogs to use litter trays, sort of like a cat.  I dont know if this is something that you might want to consider.

An enzymatic cleaner made just for pets will really help.  You can buy these at any pet store.

Good luck and hang in there! 

As adults (4 years old, you said), they will give you a hard time about housebreaking.  They have gone way too long just doing their stuff their way.  YOU are going to have to develop some major patience while working with them.   Seeking professional help isn't admitting to personal failure, simply personal lack of  knowledge.
Clyde