If your Sunbird's idle is too high or too low, the problem isn't a simple adjustment. It indicates a potential issue with one or more of these components or the PCM itself. Here's what you should check:
* Clean the throttle body: A dirty throttle body can restrict airflow and affect idle. Use a throttle body cleaner and follow the directions carefully.
* Check the IAC (Idle Air Control) valve: The IAC valve regulates airflow at idle. It might be dirty or malfunctioning. Cleaning it is often a simple solution, but replacement might be necessary.
* Inspect the air intake system: Make sure there are no leaks in the intake system. Even a small leak can significantly affect the idle.
* Check the sensors: Faulty sensors (like the MAF sensor, TPS sensor, coolant temperature sensor) can cause incorrect signals to the PCM, resulting in an improper idle. A scan tool is needed to diagnose sensor problems.
* Check for vacuum leaks: Leaks in vacuum lines can also disrupt the idle. Inspect all vacuum lines for cracks or damage.
* Check the PCM: While less common, a faulty PCM can also cause idle problems. This is usually diagnosed last.
You'll need a scan tool (OBD-I reader) to properly diagnose the issue. This will allow you to read trouble codes and check sensor readings to pinpoint the problem. Trying to adjust anything manually without understanding the system could cause further damage.
In short: Instead of adjusting the idle, you need to *diagnose* the reason why the idle is incorrect. Taking it to a mechanic or using a scan tool to diagnose the problem is the recommended approach.
