adopted 4 year old cat... wont poop in litter box

Question
Just apopted a 4 year old cat 3 months ago.  Originally i used my old cats box for him with new litter but he refused to use it.  So i got him a new one.  He will pee in it, but not poop.  If he pees in it twice, the third time is on the floor.  Thought maybe box is too small since he is a very large cat.  I put him on a stricter feeding schedule.. poops on the floor still.  Same room different spots.  Im cleaning the litter twice a day to keep him from peeing on the floor.  Seems happy?  Thought about automatic liiter box or huge litter box.

Answer
When a cats defecates on the floor, it typically is behavioral. The other reason is medical if the stool is VERY hard, indicating constipation. Have you tried placing a litter box in other areas as well as trying different litters? How often is the litter changed? as that can also be an issue. Some cats also like to have one for urinating and a second for defecating. But I would look into different locations and placing more than one around and see which location/box/litter he prefers.