Idle/stalling issue

[wright77]

My 1978 911 was running fine until a few months ago. Than when it was cold and I came to a stop, the engine stopped. After it warmed up, it was fine.
My mechanic thought the cold idle was low, so he opened up the idle speed a little. He also checked the timing and set at specs.
Now the car stalls when cold coming to a stop or between gear shifts. The engine speed simply drops to 0.
After it is fully warmed, it doesnt stall, but coming to a stop , the revs drop to around 500 RPM than pick up to 900 RPM.
The mechanic thinks the problem is the auxillary air regulator on the right side of the engine.

Any suggestions?

Thanks, Bob

[Walter_Middie]

What you describe are classic symptoms of running rich. Sounds like something is causing it to be rich. Either you are getting too much fuel, or not enough air - warm or cold.

[wright77]

Ok Thanks.

[boyt911sc]

Rob,

You could individually bench test any CIS componenets in you '78SC and avoid guess work. Plus it will save you time and money. And less aggravation in your troubleshooting. PM me and I'll give you the simple DIY procedure/s. HTH.

Tony

[longhornchris04]

Definitely sounds like running rich. I've got a '79 that did (well, sort of still does) the same thing.

I'm not sure what changed - odds are you can adjust the mixture screw on the fuel distributor a bit leaner than it is and correct most of the issues, certainly the warm running performance. All you need for that is a 3mm hex key and some patience. Make a small adjustment, drive, pop the clutch, and see if the RPMs fall "too far."

Of course, the "right" way is to ping Tony and check everything. While its clear your mixture is off, there are a number of other CIS components besides the mixture adjustment that could be set or operating incorrectly.

Oh, and weather permitting (because mine doesn't go out in the rain), I could help in person - I'm in Beavercreek. Send me a PM if you want to meet. I have the tools necessary to adjust idle and mix in my car.