Attempting to manually adjust the idle will likely damage the system and potentially lead to further problems. The idle speed is controlled by the Powertrain Control Module (PCM) based on various sensor inputs (temperature, engine load, etc.).
If your Grand Am's idle is too high or too low, the problem is almost certainly not a simple idle adjustment. Instead, you should troubleshoot the underlying cause. Possible reasons include:
* Dirty or faulty Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine, and a dirty or malfunctioning MAF will send inaccurate information to the PCM, leading to an incorrect idle speed. Cleaning the MAF sensor (carefully, following instructions) or replacing it is often the solution.
* Dirty or faulty Throttle Position Sensor (TPS): This sensor monitors the throttle plate position. A faulty TPS can cause erratic idle.
* Vacuum leaks: A leak in the intake system can cause the engine to run poorly and affect the idle.
* Faulty Idle Air Control (IAC) valve: This valve regulates the amount of air bypassing the throttle plate at idle. A dirty or malfunctioning IAC valve is a common culprit. Cleaning it or replacement may be necessary.
* Problems with the PCM: In rare cases, a faulty PCM can cause idle problems. This is usually a last resort diagnosis.
* Engine problems: More serious engine issues like low compression or a failing component can also manifest as idle problems.
Instead of trying to adjust the idle yourself, I strongly recommend:
1. Check your owner's manual: It might have some basic troubleshooting tips.
2. Use an OBD-II scanner: This will allow you to read diagnostic trouble codes (DTCs) that can pinpoint the problem. Auto parts stores often offer free code reading services.
3. Take it to a qualified mechanic: A mechanic will have the tools and expertise to properly diagnose and repair the problem. Attempting DIY repairs on the idle system without proper knowledge could lead to expensive damage.
In short: Don't try to adjust the idle. Diagnose the underlying issue causing the problem.
