Common Causes:
* Dirty or Faulty Mass Airflow Sensor (MAF): The MAF sensor measures the amount of air entering the engine. A dirty sensor provides inaccurate readings, leading to a rough idle and poor performance. Cleaning it (with MAF sensor cleaner only!) is often a quick and cheap first step. If cleaning doesn't help, replacement is necessary.
* Dirty or Faulty Throttle Body: Buildup of carbon deposits on the throttle body can restrict airflow, causing an uneven idle. Cleaning the throttle body is usually effective, but it requires careful attention to avoid damage.
* Vacuum Leaks: Cracks or holes in vacuum hoses can disrupt the engine's air-fuel mixture, resulting in a rough idle. Inspect all vacuum hoses for damage.
* Spark Plugs and Wires: Worn, fouled, or damaged spark plugs and ignition wires can cause misfires, leading to a rough idle. Check the condition of your spark plugs and wires; they may need replacement.
* Ignition Coil(s): A faulty ignition coil can prevent one or more cylinders from firing correctly, causing a rough idle. Testing the ignition coils is necessary to determine if they are the problem.
* Faulty PCV Valve: A malfunctioning Positive Crankcase Ventilation (PCV) valve can cause excessive pressure buildup in the crankcase, affecting engine performance and contributing to a rough idle.
* Camshaft Position Sensor (CMP) or Crankshaft Position Sensor (CKP): These sensors are crucial for the engine's timing. A faulty sensor can cause misfires and a rough idle.
* Oxygen Sensor(s): A bad oxygen sensor can lead to an incorrect air-fuel mixture, contributing to a rough idle. This is less likely to be the *sole* cause of a rough idle but can worsen existing problems.
* Fuel Injectors: Clogged or malfunctioning fuel injectors can deliver an inconsistent fuel supply, leading to a rough idle. This is often diagnosed with a fuel injector test.
* Engine Mounts: Worn engine mounts can allow excessive engine movement, leading to a rough idle, especially noticeable at idle. This is more of a vibration issue that *feels* like a rough idle.
Troubleshooting Steps:
1. Check engine codes: Use an OBD-II scanner to read any diagnostic trouble codes (DTCs) stored in the vehicle's computer. These codes can pinpoint potential problems.
2. Visual Inspection: Check for obvious issues like loose vacuum hoses, damaged wires, or other visible problems.
3. Clean the MAF sensor and throttle body: This is a low-cost, high-reward step.
4. Check spark plugs and wires: Inspect for wear, damage, or fouling.
Important Note: If you are not comfortable working on your vehicle yourself, it's best to take it to a qualified mechanic for diagnosis and repair. Improper repairs can cause further damage to your engine. The 3.0L V6, while robust, requires attention to detail when diagnosing and repairing issues.
