Black smoke indicates lack of air. Suggest to check the air inlet is not blocked in any way. Is there a good airflow into the room? Also the nozzle could be part blocked, dirty or worn.
iengine
February 2007
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.