Several things can cause poor draft:
1. Top of the chimney is too low, not extending above the top of the pitched roof or surrounding trees.
2. Dirt, creosote or soot lodged in corners or along the flue walls.
3. Loose mortar or cracks in the brick-work cause draft leaks.
4. Spaces between liner tiles.
5. Dislodged bricks or tile wedged in the chimney.
6. Connecting stove pipe projects too far into the chimney.
7. Chimney clean-out door too loose.
8. Leaks around chimney connector pipe.