You need to find the source of the smell and not just try covering it up.
Have you checked the gas fittings? Moved kitchen appliance around? Could be a dead mouse under a fridge or stove. Have you looked to see if the toilet is leaking? If it has septic when was the last clean out? Have you looked under the crawl space to see what is there, maybe a dead animal, mold a low spot with water in it? Could the roof have a hole in it that is allowing water to drip in or an animal to use the space asa potty/home?

There is a modular/mobile home forum...this one is more for antique houses...having lived in a place like that, there are unique issues...I would ask on the other forum.

Good luck!

We've looked for the source but can't really narrow it down.

there was definitely rodent infestation when we bought the place, but we did what we could to try to prevent them from reentering the house. My guess is there are dead mice bodies in the walls, but would that continue to smell months/years later?

We've pulled out all of the appliciances, gutted the bathroom.

Septic was emptied when we bought the house, i just put a call into the company that did it to see if they thought that the smell could be coming from that but had to leave a message.

The basement could be the problem, when it rains a lot, the crawl space gets damp and there could be standing water after really heavy rains. It will eventually drain to the sump, but the concrete floor will remain damp until we have a period of dry weather. That's why i'm putting in the dehumidifier to hopefully dry the area out quicker after rain.

Any other thoughts or advice that might help. This has been bugging the hell out of me. we want to enjoy this place in the summer and having it smell the way it does will not allow us to.

Is the roof original?

It could be leaking.

what is the "bad odor/smell"? Does it smell like poo? pee? mold? mildew? stinky men? cigarettes? skunk? pot? swamp? gas? charred wood? rotten meat? dog hair? my kid's gym shoes?

each smell has different things that could cause it, and different things that can help.

The reason I referred you to the modular/mobile home section is because they are a particularly unique sort of home. For example, my house's weird smell comes from the fact that it has a 120 year old basement...I know how to battle that...but I'm rusty on mobile homes. I know I had a crack in my bathtub in mine & the bathtub floor was rotting...but that's a particularly punky mushroomy smell.

See, there's another smell I forgot. Mushrooms! :)

Baking soda. Charcoal packs, from Lee Valley or Brita (or something bigger). That might be what sneaker odor-eaters are, but if they're different, then maybe try them. Finally, something called Nilodor.

But they're all only temporary if the source is ongoing. Mouse bodies, no should no longer smell after years.

KarinL

If you seal the concrete floor in the basement with a sealer for concrete that is used before tiling floors, it will seal the floor and get rid of the smell, if that is where it is coming from. Does the house have any exhaust fans? If you could narrow down what the smell is, then maybe you could get help solving. If it is that basement, sealing the floor may not be enough if you have water collecting down there.