I have a strong odor coming from the crawl space (about 18" high) under the house. It is acrid and earthy; strong and unpleasant. We have tested air for mold-no unusual problem. Made a french drain about 20 years ago around half of the house, still dampness in that half, but not wet or standing water. Odor comes up in bathrooms (have sealed area around plumbing), and through overflow drain in sinks.
Help! Alice

Do you have foundation vents? If so make sure they are open.
Check under house for any drips, especially around the toilet drain.

You made need to go under floor and look at it the dirt that is it may be wet and if it is you need to remove it