m104 crankcase pressure going out my oil leak?
 

My 96 E320 w/m104 used to have quite a bit of crankcase pressure when I took off the oil filler cap at idle. Now it has an oil leak I suspect to be the rear main seal (1qt every 2500 miles) and no pressure out the cap. Is all that blow by venting out the bottom of my engine? Is there harm (other than environmental) in this? THere has always been a lot of oil in the intake past the crankcase vents (car has 150k miles on it), not good for the throttle valve I am sure, so is it a silver lining the oil going out the leak instead of into the intake? I changed the plugs today they were clean but worn (around 20K miles on them I think).

Car has random misfire codes 300 and 304 I think (cyl #4) about every 500 miles when I let off the gas and then get back on it. It runs ROUGH until I stop (which I am forced to do by the rough running engine) then it runs smooth after I immediately start it back up.

TIA,
Tom

Are you sure the oil leak is at the rear main seal? That is not a common place for oil to leak on this engine.

These M104's almost always leak at the right rear corner of the head gasket (passenger side). The oil could be leaking down from there.

More than likely the misfire is caused by faulty resistors on the end of each coil.

They are cheap. Replace all 3 and see if it helps.