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1985 911 Carrera Idle Surge and Hunting

Engine

Vehicle Information: Model: 911; Year: 1985; Body Type: Targa; Engine (type, size, modifications): 3.2; Total Mileage: 122000;

After driving for a bit (not necessarily fully warm, but not cold),sometimes my idle starts surging between 1000 and 1200 rpm, about onceper second. It usually stops after 2-10 'hunts'. It usually happenswhen I come to a stop after running at speed. Once it starts, then if Iput the engine even briefly under load it will happen again (likecreeping forward at a stop sign). I can force it to stop by braking, ingear, until the idle gets really low, then clutching in. It seems as ifthere's a sticky spot when the rpm's drop down and if I get it past thatspot it's fine.The Idle Control Valve passed the diagnostics listed in my Bentleymanual, then I took it apart and cleaned it anyway. The Idle PositionSwitch also passed the diagnostics. I replaced the Cylinder HeadTemperature Sensor, which did make the car run a bit better but didn'tstop the hunting. The DME relay has been replaced recently (1998 date),although before I bought the car. Any other ideas?

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