'80 911SC low idle/stall at running temp
 

I recently acquired an '80 911SC Euro. The car seems to be spot on, but has started stalling after the car has reached normal running temp. I have adjusted the idle up a few times thinking that it was simply a loose idle screw, but it seems to be something else.

Thanks,
John

Is there anything I should add to this to help facilitate some speculation?

May be a vacuum leak. Does your idle drop when you remove the oil filler cap?

sounds like a vac leak messing up the mixture. depending on where it is, the warm-up sequence may mask it.

Another other option is your CDI box is getting flaky - as the temp goes up, the spark energy falls. This should be a problem across the rev range, not just at idle.

Idle issue
 

I have an '83. When I replaced the thermal switch in the right hand cam cover, my idle became a lot more stable.

It is a thermal/mechanical switch that sends a signal to the computer that the car is warm and needs another mixture profile.

Might be the same on an '80 Euro.

ST

Not to hijack, but is that the cam temp sensor, TT?

I will give that a try this evening.

I should have explained a bit more. Removing the oil filler cap simulates a vacuum leak by letting air into the system. If you already have a vacuum leak removing the oil filler cap will have no effect. So normally your idle will drop when you remove the cap. Finding the leak can be a fit more difficult though. Rubber vacuum lines and seals dry out and crack with age. With a nearly 30 year car there are probably multiple leaks.

Check your warm control pressures (WUR).

Also, what type of CDI do you have? There are many reports of certain Permatunes having problems when they get hot.