Here's a general guide. Always refer to your vehicle's repair manual for specific details and torque specifications. A Haynes or Chilton manual for your specific year and model will be invaluable.
Tools You'll Need:
* Socket set: Probably a 5/8" or 13/16" socket for the spark plugs (check your manual). You may need extensions and a universal joint to reach some plugs.
* Spark plug socket: A deep well socket designed for spark plugs is crucial to prevent damaging the plugs.
* Wrench: For the coil pack mounting bolts (if applicable) and any other fasteners you encounter.
* Pliers: Needle-nose pliers can help with wire routing.
* Wire brush: To clean the spark plug wells.
* New spark plugs and wires: Buy the correct type and heat range for your engine (check your manual). Ensure they are the correct length and fit.
* Grease pencil (optional): Mark wire placement before removal to prevent confusion.
* Gloves: To protect your hands from grease and dirt.
* Safety glasses: To protect your eyes.
* Jack and jack stands (highly recommended): For safe and stable access to the engine bay. Never work under a car supported only by a jack.
Procedure:
1. Disconnect the battery: This is crucial to prevent accidental shorts and electrical shocks. Disconnect the negative (-) terminal first.
2. Prepare the area: Park the car on a level surface, engage the parking brake, and chock the wheels. If you're working under the car, use jack stands for support after raising it safely with a jack.
3. Locate the spark plugs and wires: The spark plugs are usually located on top of the engine, typically under a plastic cover or coil pack. The ignition wires connect to the spark plugs.
4. Remove the coil pack (if applicable): Some Aleros had individual coil packs on each spark plug, while others had a single coil pack for multiple plugs. The manual will show you how to safely remove any coil pack(s) securing them. Take pictures or use a grease pencil to label wire positions if necessary.
5. Remove the spark plug wires: Gently pull off the spark plug wires one by one. If they're stuck, use pliers carefully to avoid damaging the wires.
6. Remove the spark plugs: Use the spark plug socket to carefully remove each spark plug. Avoid dropping them or damaging the threads. Clean the spark plug wells with a wire brush to remove any dirt or debris.
7. Install the new spark plugs: Carefully screw in the new spark plugs by hand until they are snug. Then, use the spark plug socket to tighten them to the manufacturer's specified torque (consult your repair manual). Do not overtighten.
8. Install the new spark plug wires: Carefully install the new spark plug wires onto the spark plugs, ensuring they are securely connected. If you marked the wire locations, make sure you put them back in the correct order.
9. Reinstall the coil pack (if applicable): Secure the coil pack(s) back in their original positions.
10. Reconnect the battery: Connect the positive (+) terminal and then the negative (-) terminal.
11. Start the engine: After reconnecting the battery, start the engine and listen for any unusual sounds. Check for any leaks or loose connections.
Important Considerations:
* Firing Order: The firing order is crucial. Get this information from your repair manual to ensure the wires are connected correctly. Incorrect wiring can lead to engine misfires.
* Torque Specifications: Over-tightening spark plugs can damage the engine block. Use a torque wrench to tighten the spark plugs to the correct specification.
* Gap: Check your spark plug gap specification from the manual. If needed, you can use a feeler gauge to adjust the gap correctly.
This is a simplified guide. Always refer to your vehicle's repair manual for detailed instructions and diagrams specific to your 1999 Oldsmobile Alero. If you are unsure about any step, consult a qualified mechanic. Working on your car carries inherent risks, and safety should always be your top priority.
