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1980 911SC Unstable Idle After Cold Start

Fuel System

Vehicle Information: Model: 911SC Weissach Special Edition; Year: 1980; Body Type: Coupe; Total Mileage: 63,000;

I have replaced the fuel pump, fuel pressure accumulator, warm-upregulator, all injector seals, oxygen sensor, checked all air lines,checked fuel distributor. Timing is set correctly. As far as I know, thefuel/air (CO) level is correct. When starting cold, the engine surgesfrom 2000 rpm to almost zero and does sometimes die. If I add someaccelerator pedal, it will run smoothly around 1500 rpm. After a fewminutes, it runs fine on its own. I get no surging after that point. Ihave read all of the questions submitted to you about this problem, but Iseem to have a new twist. When the car is good and warm, if I turn theengine off and immediately restart, it goes through the same surgingprocess for a few minutes again and then smooths back out. The auxiliaryair regulator was replaced awhile ago, but I think it will need to bechecked again. Is it possible that the thermal time switch could be bad?It is such a predictable amount of time for the surging sequence tohappen, that it almost seems that it could be a timed electronic problem.Also, after the engine is idling smoothly, I have not been able to getthe speed down to 950 +/- 50 rpm. I have attempted to adjust the idlespeed with the adjustment screw on the throttle body. The speed remainsthe same, even when the screw is totally closed. Does this suggestseither a bad auxiliary air regulator or a major air leak that I haven'tfound yet?

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