The flame trap just (apparently) keeps the crankcase gases from igniting. But when it isn't cleaned, it plugs up and keeps the crankcase gases from being released back into the induction cycle. Eventually they build and build until something pops. That something can usually be avoided because you'll start seeing leaks here and there, usually at the back of the head or the valve cover gasket, or eventually at the camshaft and crankshaft seals. Hopefully it didn't go this far.

It is a little piece inside of a hose that goes between the 3rd and 4th intake runners on a 1992 240. Two hoses join at that point (pull the hoses apart). One hose goes to the black intake hose right towards the throttle body. The second goes down to the engine block and the oil separator box. There is a third, small diameter hose that goes to the intake manifold.

Periodically I like to pull the white flame trap out of the housing and clean it in a solvent. In fact, clean the whole housing. You can buy flame trap kits (housing and new flame trap) for like $8 because they do get brittle.

Anyway, clean out the flame trap and poke out the little hose and it's orifices at the intake manifold and at the flame trap. They seem to get plugged. The bigger hoses are usually all right. Then find out if it is still leaking anywhere. Usually this will cure it unless something is just leaky or cracked.