Phase 1: The Basics (Cheap and Easy)
1. Ignition System: This is your top priority. Replace the following as a set (don't mix and match old and new parts):
* Distributor Cap and Rotor: These are prone to wear and carbon buildup, causing misfires. Get quality parts, not the absolute cheapest.
* Spark Plugs and Wires: Worn plugs and wires dramatically impact ignition efficiency. Use the correct heat range spark plugs specified for your engine.
2. Air Filter: A clogged air filter restricts airflow, leading to a rough idle. Replace it with a new one.
3. PCV Valve: A faulty Positive Crankcase Ventilation valve can cause vacuum leaks and affect idle. It's a cheap part, and easy to replace.
4. Check for Vacuum Leaks: Visually inspect all vacuum lines for cracks, breaks, or loose connections. Pay close attention to the intake manifold and the brake booster line. A spray bottle with carb cleaner (use cautiously!) can help detect leaks – the engine RPM will momentarily increase if sprayed near a leak.
Phase 2: If Phase 1 Doesn't Solve It (Slightly More Involved)
If the rough idle persists after Phase 1, you'll need to move on to more advanced diagnostics:
1. IAC (Idle Air Control) Valve: This valve regulates airflow at idle. A dirty or faulty IAC can cause rough idling. Cleaning it (often with carb cleaner) is a good first step. Replacement might be necessary.
2. Throttle Position Sensor (TPS): A malfunctioning TPS provides inaccurate throttle position information to the computer, leading to poor idle. It often requires a scanner to test.
3. MAP (Manifold Absolute Pressure) Sensor: This sensor measures the pressure in the intake manifold. A faulty MAP sensor can also cause poor idle. Again, a scanner is usually needed for accurate diagnosis.
4. Oxygen Sensors: While less likely to directly cause a rough idle, faulty oxygen sensors can affect fuel mixture and contribute to poor performance over time. If you haven't replaced these, it's worth considering.
Tools and Resources:
* Basic Hand Tools: Wrenches, sockets, screwdrivers.
* Owner's Manual: Crucial for specific torque specifications and part numbers.
* Haynes or Chilton Repair Manual: These manuals provide detailed instructions and diagrams.
* OBD-II Scanner: A code reader can help identify any diagnostic trouble codes (DTCs) stored in your vehicle's computer. Even a cheap one from an auto parts store will be useful.
Important Notes:
* Start with the cheapest and easiest fixes first. This approach is more efficient and cost-effective.
* Double-check your work. Loose connections or incorrect installation can worsen the problem.
* Safety First: Always disconnect the negative battery terminal before working on the ignition system or fuel system.
If you're not comfortable working on your vehicle yourself, taking it to a trusted mechanic is always an option. However, tackling Phase 1 yourself is a great way to save money and learn about your vehicle. Remember to properly dispose of used parts.
