I would buy a new litterbox (without a lid, not self cleaning). Just a regular, plain old litterbox and special litter called "Cat Attract". Confine the cat to a small bathroom or laundry room for one week and see if that doesn't solve the problem. Sometimes old litterboxes harbor set in odors in the plastics that offend cats. Many times owners get fancy litterboxes that cats don't like (either the covers are too confining, LitterMaid is too frightful, etc). And the Cat Attract litter has an additive in it that entices them to use the litter. Another thing to try is having the stool tested for un-seen parasites.
Originally Posted by Olivia's Grammy
My female, 5 years old, has started pooping out side of her box. Sometimes right in front of it. I thought maybe she was constipated so I changed cat food brands and give her hairball treats almost every night. She is still pooping out of the box 90% of the time. Fortunatly is on tile floors, but the Emmy is only 5, I don't want to clean up her poop for the next 15 years. Reggie, her brother will eat vasoline and has no problems. I have to fight Emmy to eat vasoline or the hairball stuff in a tube. They each have their own liter boxes which are cleaned every day. Advice??????