Oh boy I had this problem with Cruz when he was a puppy and even after he was neutered(not as much though). He was completely house trained, yet I would still catch him lifting his leg. He loved to "mark" pillows on the floor, fake flower arrangements and my nieces pottery barn chair!
Catching him in the act seemed to be the best way fix this habit. Sometimes I'd catch him lifting his leg (nothing comes out) and he would still do that kick thing with his back legs, like he was outside!
As far as my nieces chair though that thing is doomed. They have moved and even in their new house Cruz searches for that chair!
