I don't know anything about Jotul's but try out this web site.

www.hearth.com

Check your chimney for blockage. Sounds as if the draft is insufficient. If the chimney's clear, then wood that is not dry enough would be the prime suspect.

I have a very old Morso, non-catalytic. Mine has a smoke shelf inside above the doors. If I am burning really hot fires, with really dry wood, it sometimes fills the top of the smoke shelf with very fine ash and the stove won't draft correctly. My shelf is removeable but you need Hercules to remove it and clean it, so I usually just get some kind of a tool and scoop the ash down into the stove again. It also seems to burn less robustly if I let too much ash build up in the bottom. I had one chimney sweep who did not clean off the smoke shelf after sweeping the chimney and it really goofed up the drafting until I figured it out and cleaned the soot and ash off the shelf myself. If your chimney isn't blocked, you might check and see if you have a shelf inside at the top that has too much ash on it.