Common Causes:
* Dirty or Faulty MAF Sensor (Mass Airflow Sensor): This 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 is often a simple fix, but replacement might be needed.
* Dirty or Faulty Throttle Body: Buildup of carbon deposits on the throttle body can restrict airflow, causing an erratic idle. Cleaning it is usually effective.
* Vacuum Leaks: Small holes or cracks in vacuum hoses can disrupt the engine's air-fuel mixture, causing a rough idle. Inspect all vacuum lines for damage.
* Spark Plugs and Wires: Worn or faulty spark plugs and ignition wires can lead to misfires, resulting in a rough idle. Check for signs of wear, damage, or corrosion.
* Ignition Coil(s): A failing ignition coil can prevent one or more cylinders from firing properly, causing a rough idle.
* Crank Position Sensor (CKP): This sensor tells the engine's computer the position of the crankshaft. A faulty CKP can disrupt the timing of the engine, leading to a rough idle.
* PCV Valve (Positive Crankcase Ventilation): A clogged PCV valve can cause excessive pressure in the crankcase, affecting the engine's performance and causing a rough idle.
* Throttle Position Sensor (TPS): This sensor tells the computer the position of the throttle plate. A faulty TPS can cause an inaccurate air-fuel mixture.
* Fuel Injectors: Clogged or malfunctioning fuel injectors can cause an uneven fuel delivery, leading to a rough idle.
* Low Engine Compression: Low compression in one or more cylinders indicates internal engine problems requiring more extensive diagnosis.
* Oxygen Sensor(s): Faulty oxygen sensors can lead to incorrect air-fuel mixture.
Troubleshooting Steps:
1. Check engine codes: Use an OBD-II scanner to retrieve any diagnostic trouble codes (DTCs) stored by the engine control module (ECM). This will give you a good starting point.
2. Visual inspection: Inspect all vacuum lines, spark plug wires, and other visible components for any signs of damage or wear.
3. Clean the MAF sensor and throttle body: These are relatively easy to clean and often resolve the issue.
4. Check spark plugs and wires: Inspect them for wear, fouling, or damage. Replace if necessary.
5. If no obvious problems are found: Take your Impala to a qualified mechanic for further diagnosis. They have the tools and expertise to diagnose more complex issues.
Remember to consult your owner's manual for specifics on your vehicle's maintenance. Trying to fix it yourself without the proper knowledge and tools can lead to further damage.
