I discovered what was causing this on my 07 Newmar Mountain Air and wanted to save others some time if they have the same issue. I searched all over the web trying to find suggestions on white smoke before I tore into it but could not find anythings, so here we go:
I found two things had happened.
1. The electrodes had slipped down toward the blower about 1/16th of an inch so they were not igniting the fuel like they should. This contributed to erratic ignition or that is what it sounded like.
2. The air intake screw had vibrated loose and the gap had gradually closed enough to starve the fire, which may have also been part of the erratic ignition.
I used the metering tool screwed to the side of the blower to set the electrodes up where they belong. Change the fuel nozzle while i was in there and opened the air intake to the factory marked paint line and tighten it. Solved the problem.
Hope this helps someone. This site has saved me a lot of time and money so I always post what I find.