Intermitten Furnace problem

[EKS]

What would cause a furnace to intermittently work. The pilot works great. When the thermostat calls for heat the fan comes on but not the main burner in the furnace. It worked a week ago. Stopped working yesterday until after connections were loosened and re-tightened (in case there was an oxidation or loose connection problem). When it shut off after reaching the set temperature and the temperature was set higher the main burners would not light again.
Thanks in Advance for any help.

[Conrad]

I had similar trouble.  my solution was a new igniter board.  Seemed that my board would occasionaly decide to fire off which made me think that there might be a loose connection.  Pulling the furnace out, going over the voltages per the wiring diagram and reinstalling it... well  it worked!    TTFN