Tools You'll Need:
* Socket Set: A 5/8" spark plug socket is most common, but double-check your owner's manual. A deep well socket is highly recommended to prevent damaging the plug's porcelain insulator. A universal joint and extension will also be helpful to reach the plugs.
* Wrench: To remove the coil packs (if applicable, see below). The size will depend on your specific engine (3.1L or 3.8L).
* Spark Plug Gap Tool: To check the gap of the new plugs.
* New Spark Plugs: The correct type and heat range are crucial. Your owner's manual or a parts store can provide this information.
* Gloves: Protect your hands.
* Rags or Shop Towels: To keep things clean.
* Torque Wrench: Absolutely essential for properly tightening the spark plugs to avoid damage. Using too much force can strip the threads, and using too little can cause misfires.
Procedure (for engines with coil-on-plug ignition):
Many 1999 Grand Prix SEs have coil-on-plug ignition systems. This means each spark plug has its own ignition coil sitting directly on top.
1. Disconnect the Battery: Always disconnect the negative (-) battery terminal first to prevent accidental shorts.
2. Locate the Spark Plugs: They are usually located on top of the engine. Consult your owner's manual for precise location.
3. Remove the Coil Packs: Each coil pack is held in place by a bolt or clip. Use the appropriate wrench to carefully remove these, taking note of how they are oriented. Set the coil packs aside in a safe place.
4. Remove the Old Spark Plugs: Use the 5/8" spark plug socket, universal joint, and extension to carefully remove each spark plug. Be gentle to avoid cross-threading or damaging the spark plug.
5. Clean the Spark Plug Wells: Use compressed air or a shop rag to clean debris from the spark plug wells.
6. Install the New Spark Plugs: Carefully install the new spark plugs by hand, ensuring they are seated correctly. Then, use the socket and torque wrench to tighten them to the manufacturer's specified torque. Do not overtighten!
7. Replace the Coil Packs: Carefully reinstall the coil packs, ensuring they are properly seated and secured.
8. Reconnect the Battery: Reconnect the negative (-) battery terminal.
Procedure (for engines without coil-on-plug ignition): This is less common in a 1999 Grand Prix SE but possible depending on the engine. The process will be similar but with the added step of removing the distributor cap and rotor.
1. Steps 1 and 2 remain the same.
2. Remove the Distributor Cap and Rotor: Carefully remove the distributor cap and rotor. Note the position of the rotor relative to the distributor.
3. Remove the Old Spark Plugs: Use the spark plug socket and wrench. Remember the firing order.
4. Steps 5, 6, and 7 are largely the same.
5. Reinstall the Distributor Cap and Rotor: Make sure the rotor is in the correct position.
6. Reconnect the Battery.
Important Considerations:
* Gap: Before installing the new plugs, check the gap with a spark plug gap tool and adjust if necessary to match the manufacturer's specifications.
* Torque: Use a torque wrench and tighten the spark plugs to the proper torque specification. Over-tightening can damage the engine, while under-tightening can cause misfires.
* Firing Order: Consult your owner's manual for the correct firing order. Installing them in the wrong order can cause serious engine problems.
If you are not comfortable performing this task yourself, it's best to take your car to a qualified mechanic. Improper spark plug installation can lead to engine damage.
