The low idle and AC issues after a thermostat replacement are likely unrelated to a needing a computer reset and instead point to other problems:
* Improper Thermostat Installation: The most likely cause is the thermostat itself wasn't installed correctly. A faulty installation can lead to inaccurate coolant temperature readings, affecting the engine's idle control. Double-check your work to ensure it's seated properly and the housing is securely fastened. Air pockets in the cooling system are also common after thermostat replacement. Make sure you properly bled the system.
* Air in the Cooling System: Air in the cooling system can cause inaccurate temperature readings, leading to poor idle. Properly bleeding the cooling system is crucial after any coolant-related work. Consult your owner's manual for the proper bleeding procedure.
* Other Sensors: Replacing the thermostat might have inadvertently damaged or dislodged a nearby sensor, such as the coolant temperature sensor (CTS). A faulty CTS will give the computer incorrect information about the engine's temperature, causing problems with idle and potentially affecting the AC. Have a mechanic check for error codes.
* Throttle Body: The throttle body might need cleaning or even replacement. This is a common issue that can cause erratic idling.
* Idle Air Control (IAC) Valve: The IAC valve regulates airflow at idle. A malfunctioning IAC valve can cause low idle.
* Mass Airflow Sensor (MAF) Sensor: A dirty or faulty MAF sensor can also cause idling issues.
What you should do:
1. Check your work: Carefully re-examine the thermostat installation. Make absolutely sure it's correctly seated and the housing is properly tightened. Bleed the cooling system thoroughly.
2. Scan for trouble codes: Use an OBD-II scanner to check for any diagnostic trouble codes (DTCs). These codes will point to specific problems. Auto parts stores often offer free code scans.
3. Check sensors: Visually inspect the coolant temperature sensor and other nearby sensors for any damage.
4. If no codes appear: If no codes appear, the problem is likely related to air in the cooling system, a faulty sensor (possibly the CTS), a dirty throttle body, or a faulty IAC valve. This requires a more thorough inspection, and probably a mechanic.
Do NOT attempt any "resets" based on unsubstantiated advice. There's no general computer reset button that will resolve mechanical or sensor issues. Focus on properly diagnosing the root cause using the steps above.
