I'm talking about the blower fan, which would not help clear any gas. I'm not aware of any exhaust fan on this furnace.

I had these symptoms and it turned out to be a bad blower motor. The bushings dried up and the fan was hard to turn. It would start to run (few seconds) and then would overcurrent so the mainboard would shut it down.

No ventor motor on this furnace, it is natural draft.
Hmmm, natural draft. I think I will have a beer...

I happen to be enjoying a Red Stripe right now.;)

I replaced the upper limit switch that powers the ignition controller, it seems to have mostly fixed the problem. While the gas burner will sometimes still chatter, the gas stays on and the house is nice and warm. I suspect that the ignition controller may also be going bad, but right now everything is good. $4 later.......:D

It sounds like you got it. Sometimes the limit will fail if the filter is dirty or the return air grills are plugged (carpet over grills).