Furnace exhaust smell

Well the exhaust smell could be a simple as dust burning off the heat exchanger, or as dangerous and deadly as a cracked or rusted heat exchanger!
The puff of black smoke could be the burning off of dust also, or an old mud dabber nest.
Time to have checked out by a professional.

I totally understand your comments, and yes I will seek professional help if needed, but I do have a fair amount f mechanical ability and have done DIY projects on my homes and vehicles over the past 50 years or so. That is why I posed the question, is is maintenance or defect? Thanks

If you are a newbie with class A's then my suggestion would be contact seller and see if they can take responsibility for problem and have it looked at professionally. If not and it falls on you then I would suggest you not tinker with something you apparently know nothing about and have it looked at by a repair technician. DIY people should sometimes not tackle problems that may be beyond their level of knowledge especially when it comes to RV's