High Idle

[mtrlmngr]

Good Morning !! New Porsche owner and new to the Forum.
I recently purchase a 1977 911S that has a rebuilt 1982 SC engine. The car runs and drives fine although it needs a little help. Right now I am experiencing a high idle around 1200 when it is warm. When the weather is cold the idle is around 800 but will then surge.

Any help on where to start looking for solutions would be appreciated. Once Chicago gets some nice weather I will post some images.

Thanks

[Paulporsche]

I see that you are new, so let me introduce you to the "Search" function on this site. This topic has come up many times so you will find quite a bit of info on it.

Basically, you want to check for vacuum leaks, especially in the decel valve and hoses.

The WUR (warmup regulator) is responsible for controlling the mixture. You can check it w/ a fuel pressure gauge. You can get one from JC Whitney for the CIS or maybe borrow one from a fellow Pelican.

You should make sure your mixture is set correctly.

You should also make sure your AAR (auxiliary air regulator) and AAV (aux air valve) are operating correctly and have no vac leaks. The AAR keeps revs high during warmup, then lowers them to the correct level. The AAV assists in starting by providing extra air to raise the air flow sensor plate . Poster Mystery Train has a great thread on the AAR.

The distributor is another possibility. Old ones can get gummed up and stick. Weights and springs can wear out.

Check Jim Williams' website on the CIS. There are also books on CIS, incl one from Bosch which I think you can find online.

If I had to hazard a guess I would look into an out of spec WUR, which does not keep the mixture rich enough during warmup, which someone has tried to make up for by raising the revs.

Good luck and happy searching.

[psalt]

There is a large slotted screw on the throttle body for the warm idle speed adjustment. Just put your fingers on it and turn it clockwise to adjust the idle down to 950 rpm. Your cold idle speed should be higher than the warm idle speed. Is your 82 SC engine stock and are all the CIS lambda components properly installed ?

[mtrlmngr]

Thanks for the quick help.

As far as I know the engine is all stock. Although that is on my list of to do's. I have been waiting for the weather to break and then I was going to start diving into some of the more complex areas and see what needs to be done. based on how it is running I don;t beleive there is too much to do but until I can verify somethings I won't know that for sure.

So far I have only done some real basic fixes, I had to adjust the linkage and replace the heat cable.

Thanks again your help is greatly appreciated.