If your 1992 LeBaron 2.5L has an idle speed problem (too high, too low, rough idle), the issue likely lies elsewhere and requires a more diagnostic approach. Here's what to check:
* Clean the Throttle Body: A dirty throttle body can cause erratic idle. Remove it, clean it thoroughly with throttle body cleaner, and reinstall it. Make sure the throttle plate moves freely.
* Check the Idle Air Control (IAC) Valve: The IAC valve regulates air flow at idle. It can become dirty or malfunction. Cleaning it might solve the problem. In some cases, replacement is necessary.
* Inspect the PCV Valve: A clogged PCV valve can affect vacuum and idle. Replace it if necessary.
* Check the Mass Air Flow (MAF) Sensor: A dirty or faulty MAF sensor will give the PCM incorrect readings, leading to poor idle. Clean the MAF sensor carefully with MAF sensor cleaner (following the instructions carefully). Replacement might be needed if cleaning doesn't help.
* Check for Vacuum Leaks: Vacuum leaks can significantly disrupt idle. Inspect all vacuum hoses for cracks or damage and replace any faulty ones.
* Check the Coolant Temperature Sensor: An inaccurate coolant temperature sensor will provide the PCM with incorrect data, affecting idle.
* Have the PCM Scanned: A professional mechanic can use an OBD-II scanner (though a 1992 model might use an older system requiring a different scanner) to read trouble codes from the PCM. This can pinpoint the source of the problem. Some auto parts stores offer free code reading services.
In short: Don't look for an idle adjustment screw. Instead, diagnose the underlying cause of the idle problem using the steps above. If you're not comfortable performing these checks yourself, taking your car to a qualified mechanic is the best option. They have the tools and expertise to diagnose and fix the issue properly.
