Add the pork shoulder chunks, sliced onion, and minced garlic to the slow cooker.
Pour the orange juice and lime juice over the pork.
Sprinkle the cumin, oregano, chili powder, salt, and black pepper on top.
Cover and cook on low for 8 hours until the pork is very tender.
Use two forks to shred the pork directly in the slow cooker and stir it into the juices.
Warm the corn tortillas and fill each one with a portion of the shredded pork.
Top with chopped cilantro and serve with lime wedges on the side.