911sc idle issue

[drodg]

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?

[Bob Kontak]

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.

[Scott R]

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

[bryvincent]

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

[drodg]

Thanks everyone.

[drodg]

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.

[GothingNC]

Originally Posted by drodg

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.

[drodg]

Originally Posted by GothingNC

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

Good luck.

Thanks. I will update next week.