EGAD MAN! Flame trap is Volvo 101.

In detail - the EPA, in it's infinite wisdom, decreed that vapors in the crankcase, created by combustion products blowing ever-so-slightly past the piston rings, must never ever escape into the othewise pristine atmosphere.

So, the crankcase is sealed and a system invented to collect the vapors, separate out any oil droplets, prevent any backfires from igniting the vapors, and feeding the vapors into the intake system to burn up.

Thus the Positive Crankcase Ventilation System, aka PCV, with a flame trap in it. Test its working this way - with engine at idle remove the oil filler cap. There should be enough vacuum in the cam cover to try to pull the cap back down. If not, or if there is pressure rather than vacuum, your problem can be temporarily resolved by cleaning the PCV system.

Look on the air hose between the AMM and the throttle body for a large vacuum hose coming off on the rearward side. Follow it to the flame trap housing, which sits between intake runners #3 and #4. The housing has a small vacuum hose connected to a brass fitting on the intake manifold. The housing also has an "S" shaped hose out the bottom that goes down to the oil separator box.

Cleaning the PVC system is very simple, just clean or replace all the parts except the oil separator box. First time I would recommend getting new stuff from a dealer. All three hoses, two flame traps, and the flame trap holder. That way you can see how things hook together. If the old stuff can be cleaned up, keep for a spare set.

Check the oil filler cap vacuum after doing the job.

The whole thing should take under two hours, maybe much less. Also, the crankcase being again under vacuum can (it did for me) end a rear main seal leak, and leaks on the engine front seals, too.

Good Luck,

Bob

:>)