1. Preparation:
* Disconnect the negative battery terminal. This is crucial for safety.
* Gather your tools: You'll need a spark plug socket (usually 5/8" or 13/16", check your manual), a ratchet, extensions (various lengths, likely at least one is *essential*), a swivel or universal joint (absolutely vital for rear plug access), possibly a spark plug gap tool, and new spark plugs. A torque wrench is highly recommended to avoid damaging the threads. Gloves are also a good idea.
* Consider the space: This job is tight. You might need to work at different angles, and a mirror or flashlight will likely be helpful.
2. Accessing the Rear Plugs:
* Remove the intake manifold: This is often necessary for adequate clearance and is the most significant hurdle. This involves disconnecting various components: fuel lines, vacuum lines, electrical connectors, etc. Again, your repair manual is critical here – a wrong move can cause problems.
* Alternatively (Sometimes possible, but less likely to be fully effective): Sometimes, skilled mechanics *might* be able to reach the rear plugs without removing the intake manifold using extremely long extensions and flexible joints, but this is very difficult and increases the risk of dropping something into the engine.
3. Removing and Replacing the Spark Plugs:
* Once you have access, carefully remove the spark plug wires (take note of their order if you’re unsure, or take photos).
* Use the spark plug socket, extensions, and universal joint to carefully remove the rear spark plugs. Go slowly to avoid cross-threading or damaging the plugs.
* Install the new spark plugs to the correct torque specification (found in your repair manual). Don't over-tighten!
* Reinstall the spark plug wires in the correct order.
4. Reassembly:
* Carefully reinstall the intake manifold and all associated components. Make sure everything is securely connected.
* Reconnect the negative battery terminal.
Important Considerations:
* Repair Manual: Get a repair manual specifically for your year and model Grand Prix. This is the most important piece of advice. A Haynes or Chilton manual will be very helpful.
* Experience: If you're not comfortable working on cars, or lack the experience with this type of repair, it's best to take your Grand Prix to a qualified mechanic. This is a challenging job that can easily lead to damage if done improperly.
* Patience: This is a time-consuming job. Be patient, and take your time to avoid mistakes.
This process is a broad overview. The specific steps and difficulties may vary slightly based on the exact year and model of your Grand Prix. Again, a detailed repair manual is essential for safe and successful completion of this task.
