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EGR is the exhaust gas recirculation to ameliorate nitrogen oxides in exhaust.
The Flame Trap is part of the PCV positive crankcase system.
While both systems exist to control and reduce engine emissions, they do not intersect with each other.
Though excellent that you cleaned the flame trap and verified the PCV works.
The EGR pipe between the back of the exhaust port manifold that secures to the back of the vacuum-controlled EGR valve is sort of critical.
The large nut at the back of the exhaust manifold that retains that end of the EGR pipe can come loose. Also, there may be another, larger nut to which the nut on the EGR pipe secures. Both can come a little loose and leak.
If you see some tarry stuff around where the EGR pipe secures to the back of the exhaust manifold, there may be a very slow leak of some exhaust combustion condensates.
Also, the vagaries of air turbulence inside the engine bay with a running engine as your mighty, if awesome, 1993 Volvo 240, can deposit some leaking oil from above or in front of the EGR pipe connection at the back of the exhaust manifold.
It can help to power wash the engine bay, after giving some gunk engine bright a soak around the EGR fitting.
If you suspect a slow or very minor exhaust leak, some suds water in a spray bottle sprayed on cold, cold, cold exhaust fitting will reveal themselves as you start the engine and spray the exhaust leak suspect.
You can use, IIRC, a 22-23-24 mm open-ended spanner to verify a proper torque of the EGR pipe fitting at the back side of the exhaust port manifold.
However, be VERY CAREFUL as you do not want to twist the EGR pipe or distress it in any way. If it is rusted or has some loss of tempering (strength), you can damage the pipe to the point of breaking.
Also, some will service the EGR system as hydrocarbon and other compounds, like steam water, can condensate inside the EGR pipe behind the engine, and the second EGR pipe, that connects to the front of the vacuum-controlled EGR valve and connects to the interior side of the air intake port manifold between the #2 and #3 intake runners.
If you have a salvage yard, you may want to keep spares of the larger EGR pipe that secures between the exhaust port manifold and the aft side of the vacuum-controlled EGR valve, as well as, if fitted, spare temperature sensors. Also, you want spares of the vacuum-controlled EGR valve itself. While durable (made by Pierburg, I think), they can fail, and usually in the exhaust open position, which can reek some havoc on the engine.
If you can, the two steel EGR pipes are the same between 240, 700, 900 four-cylinder. The mid or late 1980s+ EGR valve can be thee same between these Volvo models with four cylinder. The 700/900 may use a different temperature sensor.
EGR consumes 1-2 miles per hours off your fuel economy.
If you state or nation does not require EGR on your Volvo, or because of age, visual and exhaust emission inspection may not be required, you may want to delete the EGR system complete, and change the Bosch EZK ignition ECU to one that does not integrate EGR - same for the Bosch LH-Jetronic. Though you may need to move some wire harness wires around at the ECU connectors.
A well-tended Volvo 240 normally aspired stock set up will burn nearly as cleanly, for NOx, as one equipped with EGR. As EGR reduces fuel economy by 1 - 2 MPH, well, removing it is sort of a 'meh'.
Always keep spares.
Questions?
Hope that helps.
Missouri Volvo 240 MacDuff - Suffering the State Safety Inspection.
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Jonathan Harshman Winters III: The Mightiest, Greatest, & Most Powerful Comedian, Presenter, Comedic Actor, Artist, & Author of North America in Perpetuity
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