Common Causes:
* Dirty or Faulty Idle Air Control (IAC) Valve: This valve controls the amount of air entering the engine at idle. A dirty valve can stick, causing a low idle, while a faulty one can fail altogether. Cleaning it (with carb cleaner, for example) is often a quick and cheap first step. Replacement is relatively inexpensive if cleaning doesn't work.
* Vacuum Leaks: A leak in any part of the vacuum system can disrupt the proper air/fuel mixture at idle, leading to a low idle or stalling. Inspect all vacuum hoses for cracks, holes, or loose connections. Pay close attention to hoses connected to the brake booster, intake manifold, and PCV system.
* Faulty Throttle Position Sensor (TPS): This sensor tells the engine control module (ECM) the throttle's position. A faulty TPS can provide inaccurate readings, leading to incorrect fuel delivery and a low idle.
* Dirty or Faulty Mass Airflow Sensor (MAF) Sensor: This sensor measures the amount of air entering the engine. A dirty sensor (clean it carefully with MAF sensor cleaner) or a faulty one can lead to an incorrect air/fuel mixture and a low idle.
* Faulty PCV Valve: A clogged Positive Crankcase Ventilation (PCV) valve can cause a vacuum leak or build up pressure, affecting the idle.
* Low Engine Compression: If the engine is losing compression, it might struggle to maintain idle speed. This is a more serious issue requiring a compression test.
Less Common Causes:
* Problems with the Engine Control Module (ECM): A faulty ECM is less likely but possible. This would usually require professional diagnosis and potentially replacement.
* Fuel Delivery Problems: Issues with the fuel pump, fuel filter, or fuel injectors could contribute to a low idle, but these usually manifest with other symptoms like poor acceleration or rough running.
* Ignition System Problems: Problems like faulty spark plugs, wires, or the distributor (if applicable) could lead to a rough idle or misfires, which could manifest as a low idle.
* Intake Manifold Gasket Leaks: Leaks in the intake manifold gasket can cause vacuum leaks, affecting the idle.
Troubleshooting Steps:
1. Start with the simplest and cheapest fixes: Clean the IAC valve and check for vacuum leaks. These are often the culprits.
2. Use a code reader: A scan tool can read any diagnostic trouble codes (DTCs) stored by the ECM, pointing towards specific problems. Auto parts stores often offer free code reading.
3. Consult a repair manual: A repair manual specific to your 2002 Chrysler Sebring will provide detailed information on diagnosing and repairing these issues.
4. Seek professional help: If you're not comfortable working on your car yourself, take it to a qualified mechanic for diagnosis and repair.
Remember that identifying the exact cause of a low idle often requires systematic troubleshooting. Start with the most likely causes and work your way down the list. Safety first – disconnect the negative battery terminal before working on any electrical components.
