How do you change the idle speed on my 97 Chevy Lumina?

You can't directly adjust the idle speed on a 1997 Chevy Lumina like you might on older carbureted cars. The idle speed is controlled by the PCM (Powertrain Control Module) through a sophisticated system involving sensors and actuators. Trying to manually adjust it will likely be ineffective and could damage the system.

Issues with idle speed on a '97 Lumina are usually caused by problems with one or more of these components:

* IAC (Idle Air Control) Valve: This valve regulates the amount of air entering the engine at idle. A dirty or malfunctioning IAC valve is a common cause of erratic idle. Cleaning it is often the first step in troubleshooting. Replacement is necessary if cleaning doesn't fix the issue.

* TPS (Throttle Position Sensor): This sensor tells the PCM the position of the throttle. A faulty TPS can cause incorrect idle speed and other drivability problems.

* MAF (Mass Air Flow) Sensor: This sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor can lead to incorrect fuel delivery and affect the idle.

* Vacuum Leaks: Leaks in the vacuum system can disrupt the proper operation of the idle control system. These can be difficult to find.

* Engine Coolant Temperature Sensor: The PCM uses the coolant temperature to adjust the idle speed. A faulty sensor can cause incorrect idle behavior.

* PCM Issues: In rare cases, a faulty PCM can be the culprit. This is usually diagnosed last, after other components have been ruled out.

Instead of trying to adjust the idle speed directly, you should:

1. Check for trouble codes: Use a OBD-II scanner to read any diagnostic trouble codes (DTCs) stored in the PCM. These codes can pinpoint the source of the problem.

2. Clean the IAC valve: This is often a simple and effective fix. Consult a repair manual for your specific vehicle to learn how to access and clean it. Be careful not to damage it.

3. Inspect for vacuum leaks: Carefully examine all vacuum hoses and connections for cracks or leaks.

4. Have a mechanic diagnose the problem: If you're not comfortable working on your car's engine, take it to a qualified mechanic for diagnosis and repair. Attempting repairs without proper knowledge can lead to further damage.

Adjusting the idle speed directly is not a recommended procedure for this type of fuel-injected engine. Focusing on diagnosing and fixing the underlying cause is the correct approach.