kitten/cat keeps toileting on the carpet

Question
My cat/kitten is 4 months old, litter box trained and also goes to the toilet outside as well. Has started pooping on the carpet in one specific place (my daughters room) only over and over, despite clean litter and outside access being always available. I have washed the carpet with soap powder and left dried soap powder on the carpet to deter him. I have tried sprinkling pepper in the corner he does it in. I have tried putting a small bowl of dry cat food in that area after a good carpet shampoo as i read they will not poop near their food. Someone tell my cat please because he just pooped right next to the bowl of food! Shutting the door constantly is really not possible as this is a 3 yr old childs bedroom.

Any help appreciated.

Answer
The only thing that might have started this was a change in litter materials or too much noise in the area where he goes.
A litter box in a 3 yr old child's room is not the appropriate place for one.
It should be in a quiet corner of the house away from where everyone walks and runs and makes noise.
When a cat is suddenly not using the box that means he is not happy with the location of it and or the contents.
Make sure it is cleaned regularly also- I mean the whole thing dumped out and refilled.

Another thing you can do for that one spot is use foil on the carpet. Cats do not like the feel of aluminum foil on their feet.

And yes, if they are unhappy, they will poop by their food.