Engine rough idle

Richard Stephens, Register Technical Advisor, reports 
If you have had your 911 SC engine hunting up and down when started from cold or it has a rough idle, then here are few thoughts about the subject. I have a 1978 model 911 SC (built June 1977), which has had this problem on cold start. I purchased it in 1993 and, in winter when it was cold, the engine hunted around a lot at first start-up. People thought I was purposely blipping the throttle to make lots of noise!