True Confessions - Oopsies, it didn't work
 

You may recall my announcement that I finally found it ! the reason I can't check my oil with the engine running and the cap off.

https://forums.pelicanparts.com/porsche-911-technical-forum/1107581-911sc-stall-idle-oil-filler-cap-off.html

Well it worked , when the engine was cold-ish, but it was snowing outside, so tested in the garage only, with the door open , of course.

So, yesterday , I had the opportunity to take the car out, get it up to temp, and try it again. No deal, died right away.

The idle has always been at 1100 , can't get it any lower, even with it all turned in. That makes me think it must be a pesky air leak somewhere.

So, here we go again, I'll be looking for the dreaded air/vacuum leaks all over again, but I'll wait until the weather warms up a little .

Yea, vacuum leaks are sometime really hard to find. A real smoke test is often the only way to find them. Often the intake is the source of the leak.

Try pinching the brake booster hose. They can crack where they go over the torsion tube.

Undetected vacuum leak........
 

Scot,

You have undetected vacuum leak/s with your CIS. Why would your cold idle not go over 1300 RPM this time of the year? If the ambient temperature is below 50°F, your initial cold idle should be high (1300~1400 rpm). What is you cold control pressure?

Without using a smoke generator, you will be lucky to find or identify those hard to see leak sources in your CIS. You must create a positive air pressure inside the airbox with smoke to be able to find them. It takes only a couple of seconds to locate the culprit/s provided you have the right set up. Keep us posted.

Tony

My first knee jerk is that the restrictor (930-107-289-00) in the big crankcase to oil tank breather hose is missing but that wouldn't explain the 1100 idle. Still worth checking for the restrictor.

I had the same issue after repairing a blown air box revs at 1100 with idle adjustment fully clockwise. There is no real shortcut when it comes to finding vacuum leaks. Built a cheap smoke tester and found several injectors leaking. Bought new injector sleeves and new O-rings,re-staked the sleeves. Retested and then re-adjusted the CIS system with gauges.