We can't say
It should make for a nice improvement, but we are not in the house and can't say for sure. Normally the two recommended steps will solve the problem. But if there is another problem of negative pressure on that floor then no, the problem may not be completely solved. Is the insert normally easy to light or reload with no smoke spillage? If so, the odds are in favor of the cleanout and liner stopping the problem. If there is some spillage typically, then this could be a negative pressure zone. It's that 4th floor that makes it a bit hard to answer where the neutral pressure point is in the house.So just to be clear. Do you all believe that putting in the liner will be able to stop the actual problem of air flowing down the chimney constantly?
Or is it just going to be flowing downward with less odor?