911sc idle issue
 

When I drive my car for the first 15-20 minutes the car idles around 1000rpm as it should but as it warms up it has a tendency to start idling higher. I can bring the idle down by letting the clutch pedal out with the car in gear say as I come to a light. I am wondering what I should look at first?

Try the decel valve. It is on the passenger side. Closest cadmium plated "flying saucer" to the rear of the car. The lower one. Has a small hose going to it. If you plug the hose with a nail it may help.

Let us know if that does anything. You are probably sucking false air somewhere and this may be the culprit.

Second the "false air" issue. Typical cause of this.

i have the exact same problem a couple months ago which i finally "cured" but i don't know exactly which did the trick as i did a couple of things at the same time.
first i changed the o2 sensor relay and then i tried clamping the decel valve with a long jaw vise grip and tried to bang it too and finally, (i think this one did the trick) i patched a big crack on the cat converter pipe near the o2 sensor with those exhaust leak putty. took it for a drive the next day and no more high idle when warmed up.
i don't really know but i think that big crack on the cat pipe maybe sucking fresh air on to the o2 sensor resulting a false o2 reading. if not maybe hitting the decel valve with a vise grip did the trick:D

Thanks everyone.

Just an update. I opened the oil dipstick/fill and the idle drops. I think this is indicative of a vacuum leak? We are going to start exploring in the next few days as I got a tune up kit from our host and I want to try to get this resolved at the same time.

That is normal, if the idle did not drop, you have a vacuum leak.

Good luck.

Thanks. I will update next week.