1. Loose or Faulty Battery Connection: Ensure the battery terminals are securely connected and there is no corrosion or damage. A loose or faulty connection can affect the electrical system and cause idling issues.
2. Reset ECU (Engine Control Unit): Disconnecting the battery may have reset the Engine Control Unit (ECU). Sometimes, the ECU needs to relearn the optimal air-fuel mixture and idling settings. Give the car some time to run and allow the ECU to adjust.
3. Throttle Body Issues: A dirty throttle body can cause idling problems. Try cleaning the throttle body using a throttle body cleaner. Make sure to follow the manufacturer's instructions carefully.
4. Vacuum Leaks: Vacuum leaks can also lead to rough idling. Check for any loose or cracked vacuum hoses in the engine bay and replace them if necessary.
5. Fuel System Problems: Check the fuel filter and fuel injectors. A clogged fuel filter or faulty fuel injectors can affect fuel delivery and cause idling problems.
6. Faulty Idle Air Control (IAC) Valve: The IAC valve controls the amount of air that enters the engine when idling. A malfunctioning IAC valve can cause idling issues. Consider cleaning or replacing the IAC valve.
7. Oxygen Sensor Issues: A faulty oxygen sensor can provide incorrect feedback to the ECU, affecting the air-fuel mixture and causing idling problems. Check the oxygen sensor and replace it if needed.
8. Other Sensor Problems: Other sensors, such as the coolant temperature sensor, mass air flow (MAF) sensor, or crankshaft position sensor, can also impact idling. Have these sensors checked and replaced if necessary.
Since your check engine light is on, it's advisable to have the car scanned for diagnostic trouble codes (DTCs) using an OBD-II scanner. These codes can provide more specific information about the underlying problem and help you identify the exact cause of the idling issue.
If the problem persists after checking these items or if you feel unsure about working on your car's engine, consider taking it to a qualified mechanic or an authorized Hyundai dealership for inspection and repair.
