No, Toa of Fire can't control lava. If they can absorb enough heat to freeze water, though, I expect they could freeze lava into stone by absorbing heat from it.
But in conjunction with a Toa of Earth or Stone, that makes sense. Hm, by that logic, I wonder if a Toa of Fire and a Toa of Ice together could control water.
Ehh... No, somehow it just doesn't seem right though. I can see Fire and Water controlling steam, and Air and Water making a thunderstorm, Air and Earth sandstorm, Ice, Water and Air snowstorm (Or Fire, Water and Air, if the Fire Toa is capable of absorbing heat on that scale), Earth and Fire making glass,, Stone/Rock and Fire controlling lava, etc., but really I doubt that Toa can control other elements, I think that even with combined power, they can only create or destroy them, and that only in certain cases. For instance, Fire/Ice can create or absorb water. 'Ice creates, Fire heats,' or 'Fire sucks heat, Ice absorbs the ice itself' respectively.
But, also, couldn't Light and Shadow theoretically create an infinite loop of absorption?