I have never run anything but white gas through it. Please help, before I take out my frustrations on it.
Chances are it has broken loose and is causing something akin to a backfiring car muffler.
Tell them you ve already spoken to a Coleman technician, who says you need a new burner unit. Have the model number for your lantern handy. It sounds as if the lantern arrived in your hands with a defect. If this is the case, Coleman says they ll ship you a new unit at no charge.