I have a very old 1986 furnace and it is not burning well. It produces a yellow flame, a lot of soot, and strong smell that feels like it's lacking oxygen to burn. What would it be?
Not to seem curt, but it would be time to consider a new furnace. I can't say for sure without testing, but it sounds like you have a bad heat exchanger and that can be dangerous if it, in fact, is what is the problem.
Updated on February 6, 2018
By Dan Robbins