Weird Observations about my High Idle Issues...

[86 911]

As you all know from my 5 or so threads on Pelican regarding this issue, I have a high idleing problem with my 78 3.0 SC. Sometimes the car will start up and the RPM's will creep from idle to 2000 RPM in a matter of seconds, but other times it takes longer, say 5-10 minutes for the engine idle to get to 2000 RPM. Also over the weekend I went for a pretty long drive and I noticed something unusual. My idle was up at 2000 RPM as usual, but when I stopped at a stoplight, the idle creeped DOWN to 1200 RPM or so . Good News! By the next stoplight, the idle was down to about 1000 RPM. After that, I parked the car for a few hours, came back to it and it idled at 2000 RPM as usual on the way home. What does this sound like to you?
I've already replaced the AAR and WUR, and checked the throttle linkage. Would this be a vacuum leak, even with this high idle - low idle issue or something else?

[SP2]

Matt,

I am a newbie for a few months now, but I thought I read somewhere that the idle is supposed to be 2000 when the car is cold. Something about a cold start mixture. To prevent backfiring when cold? My car is always 2000 when cold, and then about 1200 when at operating temperature.