high idle speed after warm up
 

Hey,
I have a 79 930 turbo with a problem that just started recently.
The car starts fine and idles from cold at 1000rpm. As I let it warm up and blip the throttle, the idle speed gradually increases to 1800rpm or so and will not drop back to normal 1000rpm.
Eventually after a drive on the highway and fully warmed up it will not idle below 2000rpm. I noticed this happening only after driving for a few hours on the highway and comming off the off-ramp the car would not idle below 2000rpm last week.
Now the throttle pedal is not hanging up as it returns to the end stop fine. I have not gone under the car to see if the thottle cable, bell crank is hanging up, but I don't think this is the issue.
Anyone have ideas on the cause? What should I check? I have a DE event coming up next week that I need to fix this right away or I am screwed.

I don't think you're screwed unless you're telling us "This funny thing that looks like a piston is hanging on the ground below my engine..." Then you're screwed. Otherwise, pull the Auxiliary Air Regulator and see if it's jammed closed/open. That's where I'd start.

I guess screwed is a relative term then.
Can I pull the AAR and plug the connections and run the car with out it?
I am assuming that if it is malfunctioning then I will not be able to rebuild it or buy a new one in time for the DE event.
It would be nice to know if the car will run without it and what effect it would have on driving the car.

Fred-

Scroll down one post - there's a informative discussion on the AAR, it's removal, etc.

Short version: pull / plug it and see if that's your culprit. Good luck, and enjoy your DE!

I'd pull off the oil filler cap and make sure you don't have lots of blow by.

Great news. I pulled the electrical connector from the AAR valve body to check for power and it was full of oil. Cleaned it up and reconnected and the car now runs fine. High idle during initial start for 1-2 minutes and then backs down to 900rpm.
I did run it with the AAR valve plugged and it would not idle more than 600rpm or so. I did not want to remove it form the system and readjust the idle speed unless absolutely it had failed.
How do you readjust the idle speed on these turbo CIS anyway? I did not see an air bleed screw with all the intercooler and air filter installed?

How would this make for a high idle?

Because the blow by pressurises the intake by the hose that is meant to burn any off.

Nathan,
Isn't the oil tank fed the hose from the crankcase and then this returns thru another hose to the air cleaner housing? High blowby in the oil tank would then be passed thru the air cleaner housing upstream of all the compensating devices....this would need to be alot of blow by in order to pressurize the air filter housing any appreciable amount.
Just my thoughts.....I cannot see all the hoses the way they are routed behind the air filter housing, but that is how I suspect it is routed...normally aspirated 911SC done that way.

Anyway, how do you adjust the idle speed on the turbo anyway.....where is there an air bypass screw?
Cannot see it currently.

You may be right, I know most cars are like I stated but that would be typical of Porsche to do it different :)

There is a screw on the TB. You may need to remove stuff to get at it.