Here's a breakdown of potential causes and how to address them:
1. Idle Air Control (IAC) Valve: This is the most common culprit. The IAC valve regulates air flow at idle. A dirty or malfunctioning IAC valve can cause a high idle.
* How to troubleshoot: Inspect the IAC valve for visible dirt or debris. Try cleaning it with carburetor cleaner (following the can's instructions carefully). If cleaning doesn't solve the problem, it might need replacement. Some IAC valves can be tested with a multimeter (check your vehicle's service manual for specifics).
2. Throttle Position Sensor (TPS): The TPS tells the computer the throttle's position. A faulty TPS can send incorrect signals, leading to a high idle.
* How to troubleshoot: A multimeter is needed to test the TPS voltage output. Consult your service manual for the correct voltage readings and testing procedure. A bad TPS needs replacement.
3. Mass Air Flow (MAF) Sensor: The MAF sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor can cause incorrect fuel mixture calculations, leading to a high idle.
* How to troubleshoot: Carefully clean the MAF sensor with MAF sensor cleaner (never use anything else!). A severely damaged MAF sensor needs replacement. Again, a multimeter might be used for testing (refer to your service manual).
4. Vacuum Leaks: Leaks in the vacuum system can disrupt the engine's idle control.
* How to troubleshoot: Visually inspect all vacuum lines for cracks, holes, or loose connections. Use a vacuum gauge to check the vacuum pressure at idle; a significantly low reading indicates a leak. Repair or replace damaged vacuum lines.
5. Throttle Body: A dirty throttle body can restrict airflow and affect the idle.
* How to troubleshoot: Remove the throttle body and clean it thoroughly with throttle body cleaner. Make sure to pay attention to the throttle plate and its pivot point.
6. PCV Valve: A clogged Positive Crankcase Ventilation (PCV) valve can cause excessive pressure in the crankcase, affecting the engine's operation, including idle speed.
* How to troubleshoot: Remove and inspect the PCV valve. A clogged valve should be replaced.
7. Engine Coolant Temperature (ECT) Sensor: A faulty ECT sensor can provide incorrect information to the engine control unit (ECU), leading to a variety of problems, including high idle.
* How to troubleshoot: The ECT sensor can be tested with a multimeter. Consult your service manual for the correct resistance readings at different temperatures.
8. Computer (ECU) Problems: While less common, a faulty ECU can also cause a high idle. This is the hardest to diagnose and usually requires professional help.
Important Notes:
* 1992 Dodge Stealth Service Manual: Obtaining a factory service manual is highly recommended. It contains detailed diagnostic procedures and specifications for your specific vehicle.
* Professional Mechanic: If you're not comfortable working on your car's engine, take it to a qualified mechanic. Improper repairs can cause further damage.
* Start Simple: Begin with the easiest and most likely causes (IAC valve, vacuum leaks, dirty throttle body) before moving on to more complex components.
Remember to systematically check each component, one at a time, and document your findings. This will help you identify the root cause of the high idle and get your Dodge Stealth running smoothly again.
