manually under the hood.
Because something is broken, or your idle speed has been set WAY to high. Try to fix this soon.
May be idle position sensor.
The idle is automatic. If the speed is not corect then you have to fix the problem with the idle motor.
Idle speed set too high most likely. Also could be carbon deposits inside cylinder. There are a few other option, but the cheapest to check and fix is idle speed.
fix the vacuum leak
U need to clean the throttle body and also clean the idle air control vavle
The idle speed is computer controlled. You need to scan the pcm for faults, read it sensor data, and decipher why the idle is incorrect to repair.
To fix high idle problem on a 1996 VS Commodore, first locate the idle air control valve. Unscrew and unplug electrical connector running to the valve. Turn the valve over and clean the sensor for debris.
Look on the carburetor on left or right side. On it, look for a gold/brass colored screw with a spring on it. Turn in and out to adjust the idle speed. Nothing can be damaged with this as the importent screw jet screws are out of way and not easy to get at.
You can't adjust it, you have to replace either the IAC ( idle air control ) sensor or the TPS ( throttle position sensor ) to fix a bad idle.
go to autozone for a free diagnostic check & the computer will tell you what is wrong ie map sensor. idel air control . mass airflow sensor
tps throttle position sensor