[scotty305]

The engine needs a certain amount of air to idle at a certain speed. There are quite a few possible air paths into the engine, depending on how you look at things:

1. Main throttle stop. This can be adjusted using a set screw. I'll have to double-check but I think it's on the front of the throttle (closer to the front of the car).
2. Fast idle cam. This is on the rear (firewall side) of the throttle and uses a thermo-wax pin to increase the throttle stop (from the back side of the throttle shaft) and allow additional airflow when the engine is cold.
3. Air bypass screw. This near the bottom of the throttle, and can only be seen with the intake elbow removed.
4. Idle Speed Control solenoid, located on the rear of the upper intake manifold. The ECU can vary a certain amount of airflow by opening this solenoid valve between 0-100%.
5. Accelerated Warm-Up Solenoid (AWS), located under the upper intake manifold. The ECU can open or close this solenoid.
6. Vacuum leaks can allow air past the throttle and cause the car to idle high.

Items 1-3 could be manually adjusted to compensate for a vacuum leak. The stock ECU may not be able to reduce total airflow enough to compensate for a large vacuum leak.