Common Causes:
* Vacuum Leaks: A vacuum leak can disrupt the air/fuel mixture, causing erratic idle.
* Dirty Idle Air Control (IAC) Valve: The IAC valve controls air entering the engine at idle. If it's dirty, it can't regulate airflow correctly.
* Faulty Throttle Position Sensor (TPS): The TPS tells the computer the throttle position. A faulty sensor can provide inaccurate information, leading to fluctuating idle.
* Clogged Fuel Injectors: Clogged injectors can cause inconsistent fuel delivery, affecting idle.
* Faulty Oxygen Sensor (O2 Sensor): An O2 sensor that's not functioning correctly can send inaccurate feedback to the computer, leading to engine fluctuations.
* Dirty Air Filter: A clogged air filter restricts airflow, potentially impacting idle speed.
* Faulty or Dirty Mass Air Flow (MAF) Sensor: The MAF sensor measures the amount of air entering the engine. If it's dirty or faulty, it can cause erratic idle.
* Faulty Ignition System: A weak spark or faulty ignition components can disrupt combustion, leading to idle issues.
* Engine Coolant Temperature Sensor (ECT Sensor) Issues: A faulty ECT sensor can cause the computer to incorrectly adjust fuel/air mixture, impacting idle.
Troubleshooting Steps:
1. Check for Vacuum Leaks: Listen for hissing sounds around hoses and intake manifold. Visually inspect hoses for cracks or loose connections. Use a vacuum gauge to check for leaks if you suspect any.
2. Clean the IAC Valve: Disconnect the electrical connector and remove the valve. Clean it with a spray carburetor cleaner, making sure to remove any debris.
3. Inspect the TPS: Use a multimeter to check the TPS voltage output. If it's not within the specified range, replace the sensor.
4. Check Fuel Injectors: Have the injectors cleaned and inspected. You can also test them with a fuel pressure gauge to ensure proper fuel delivery.
5. Inspect the O2 Sensor: Replace the O2 sensor if it's old or shows signs of damage.
6. Replace Air Filter: Ensure the air filter is clean and free of debris.
7. Clean the MAF Sensor: Use a MAF sensor cleaner to carefully clean the sensor element. Avoid touching the sensor wires.
8. Inspect Ignition System: Check spark plugs, wires, distributor cap, and rotor for wear or damage.
9. Check the ECT Sensor: Test the ECT sensor with a multimeter. If it's not within the specified range, replace the sensor.
Important Notes:
* Consult your Cadillac's repair manual for specific instructions and specifications.
* If you're not comfortable performing these repairs yourself, it's best to take your vehicle to a qualified mechanic.
* A scan tool can be helpful for diagnosing engine codes and providing further insight into potential issues.
