I was checking my oil level today and noticed my idle (RPM's) did not decrease as I removed the oil cap. I remember this being true on my SC, Carrera and 964. Does this apply to 993's?

My idle is low (approximately 600) and does not stall. I do have a LWF and never experienced any stalling as well. When my AC is turned on, my idle does increase to where I feel the idle should be w/o it on.

I've checked vacuum leaks, hoses, etc... to confirm if I have a leak elsewhere. Car runs great and burns minimal oil. I have no CEL indicating any codes whatsoever!

So back to my original concern; should my idle drop when I remove the oil cap? Would this indicate a vacuum leak somewhere? Should I replace the oil cap?

 

no, it shouldn't.

my car idles low as well, but I believe thats because of a slightly inaccurate tach.

 

some times removing the oil cap would create a vacuum leak...not sure on 911s but know this is true for my Audi RS4. Even the dip stick gasket going bad on the RS4 can cause a vacuum leak.

 

I've never noticed a decreased idle when removing the cap.



Andreas

 

If the oil cap is on the engine itself (i.e. not a true dry sump), then the engine will breathe unmetered air through the crankcase ventilation system (a vacuum leak).

This is not the case on the 993.

 

I cleaned my ISV and even adjusted it a couple degrees.



However, as others mentioned here the ECU will just adjust it back to where the idle was prior.

The next thing I'll do is r&r caps and rotors, check plug wires and spark plugs.

Thanks for your comments!