Common Causes:
* Dirty or Faulty Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine. A dirty MAF sensor provides inaccurate readings, leading to a poor air/fuel mixture and a rough idle. Cleaning it (carefully, with MAF sensor cleaner) is often a first step.
* Dirty or Faulty Throttle Position Sensor (TPS): The TPS tells the engine control module (ECM) the throttle's position. A dirty or faulty TPS can cause erratic fuel delivery, resulting in a rough idle.
* Vacuum Leaks: Leaks in the intake manifold gaskets, vacuum hoses, or other vacuum-related components can disrupt the engine's air/fuel mixture, causing a rough idle. This often presents as a rough idle, particularly noticeable at idle and/or during acceleration.
* Faulty Ignition System: Worn spark plugs, spark plug wires, or a failing ignition coil can lead to misfires, resulting in a rough idle.
* Dirty or Clogged Fuel Injectors: Clogged injectors can deliver an inconsistent amount of fuel to the cylinders, causing a rough idle. Cleaning or replacing them may be necessary.
* Failing PCV Valve: The Positive Crankcase Ventilation valve helps remove pressure from the crankcase. If it's faulty, it can introduce contaminants into the intake system, affecting the air/fuel mix.
* Low Engine Compression: Worn piston rings or valve issues can lead to low compression in one or more cylinders, leading to a rough idle. This is usually accompanied by a loss of power.
* Throttle Body Issues: A dirty or sticking throttle body can restrict airflow, leading to a rough idle. Cleaning it is often beneficial.
* Oxygen Sensor (O2 Sensor): A faulty O2 sensor provides inaccurate readings about the exhaust gases, affecting the air/fuel mixture and causing a rough idle, or poor fuel economy.
Troubleshooting Steps:
1. Check Engine Light: If the check engine light is on, have the codes read using an OBD-II scanner. This will provide valuable clues about the problem.
2. Visual Inspection: Check for obvious vacuum leaks, loose or damaged wires, and other visible issues.
3. Clean MAF Sensor: This is a relatively easy and inexpensive first step.
4. Clean Throttle Body: Another relatively simple procedure that can often solve idle issues.
5. Check Spark Plugs and Wires: Inspect for wear, damage, or fouling.
Important Note: Unless you have significant automotive experience, it's best to have a qualified mechanic diagnose and repair the problem. Incorrectly diagnosing and attempting to repair engine issues can lead to further damage and potentially costly repairs.
