Pooping outside his box

Any ideas why my cat may be pooping outside his catbox?  He just went for the third time in 4 days.  He walked in the box, then walked right out and pooped on the floor.  I just changed the bag yesterday, so everything is clean and the litter is fairly deep.

As far as behavior, otherwise he is still the same guy.  Running around like crazy, eating, sleeping, his poop looked normal and smelled normal.  He wasn't straining or anything.  Thanks

It really does sound like he didn't want to go in the box, doesn't it? How about trying another box? 

Many cats won't wee where they poo and vice versa, and they may decide that's the way they're going to do it at any time, even if they used one box for both before.

I hope it is behavorial.  Yet, I was thinking.  I was scooping his box and I cannot recall whether he has pooped or not today.  I think he may have only urinated.  I'll have to set my alarm early and if he doesn't poop, I may just take him in.  If he doesn't poop by noon, then that will be a definite 24 hours of not going, and ask his vet if that may be related to pooping outside the box.

Do you only have the one box? The rule of thumb is 1 more box than you have cats. My 3 for some reason rotate which box they are using from day to day. I haven't figured out the schedule but before I put in the last box there were problems. Now everyone is happy. Go figure.

how many boxes and how big, and what type litter

Our kitten, Darwin, would act out by going just outside the box. The feline specialist we took him to recommended Dr. Elsey's Cat Attract litter. He watched as my husband put the new litter in, and within a few seconds, he hopped in and hasn't had an accident since. The litter is a bit more expensive, but there's a $1 coupon in every box and PetsMart sometimes puts it on sale. Give it a try and I think you'll be pleased.

Mother Dragon said:

 
Our kitten, Darwin, would act out by going just outside the box. The feline specialist we took him to recommended Dr. Elsey's Cat Attract litter. He watched as my husband put the new litter in, and within a few seconds, he hopped in and hasn't had an accident since. The litter is a bit more expensive, but there's a $1 coupon in every box and PetsMart sometimes puts it on sale. Give it a try and I think you'll be pleased.

Click to expand...

and there is a rebate form

http://www.preciouscat.com/wp-content/uploads/2014/07/FINAL-Free-Litter-Fax-Form-7-2014.pdf

He uses Arm and Hammer Double Duty. I know scented litter isn't good, but he's like obsessed with the litter. If I bring a box in the room he'll do what he can to get it open. He'll swat at it and bite it and climb on top. If it is open, he'll dig his paws in and go all crazy.