73 2 liter PCV valve questions, Need some help on what parts are missing Options

[Marcel Aircooled]

OK, I am trying to eliminate some possible air leak sources causing slightly higher rpm on my 1973-1974 2 liter 4 cylinder US GA code engine with D jetronic FI system.

Looking at the PCV valve I have and the Porsche parts diagram it looks like I am missing some parts. Mine is just screwed on with the white nut without any seal or o ring (#8 in below diagram) and the hose comming from the manifold is connected directly to the pcv without any elbow piece like #14 in the diagram. Also the stopper part (#9) is missing. Could the missing seal, elbow and/or stopper be causing a (small) air leak? My engine is running 100-150 rpm too high when idling and when I close the hose coming from the pcv with a pair of pliers the rpms drop to about 900.

Also my oil filler cap does not have any seal as shown in the diagram (bottom part of #2). Should there be a seal and if yes what type?

Here's a picture of the parts I have (white plastic nut is not shown)


And here's a screenshot of the Porsche parts diagram


and the part numbers


Thanks for reading and for any advise!

[emerygt350]

My 73 2.0 has a straight pcv valve which I think is normal. #12 in that diagram. An elbow of some sort maybe have been lost over the years, but I have not seen one on other active pcv cars. Later years went to a passive pcv so no valve and that same hose would just go to the cleaner box rather than the manifold.

It sounds like your PCV is working correctly if you are looking at a 150 rpm drop when you plug it. It was designed that way, it has little bleed passages that allow vapor to be pulled off the engine at idle, it doesn't really start pulling hard till the vacuum drops in the plenum when more gasses are expected to be produced.

I suspect your high idle is due to something else. Grab a can of carb cleaner and start spraying. Is your idle screw all the way in? If so, put your finger over the passage inside the throttle body that leads to that idle screw. Mine never seats completely and causes an idle bump (which I get by with just closing it completely which is probably the same as most people half turn open).

If your TB isn't leaking terribly at the butterfly bushings and your plenum seals are all good, and that elbow where the PCV hose connects to the plenum is good (check all that with the carb cleaner) then I would look towards your timing and temperature sensors.



Are you still using the original adv/retard distributor?

And yes, you do want that rubber gasket in the filler lid.

This one is from a 1.8

[Marcel Aircooled]

Thanks emerygt350, I don't see the elbow used much either when I search for PCV valve pictures. I have an electronic 123ignition so no original distributor anymore. I already replaced some hoses and had my MPS redone by Bosch and replaced the throttle body gasket which eliminated large part of the rpm issues. Idle screw is completely in like yours but does still show a gap where air passes. I have another TB with screw and it is the same so guess the screw never closes completely?

Will add a gasket to the oil filler cap. Do you know if there is a seal between the PCV valve and the filler housing?