What You'll Need:
* New Spark Plugs: Make sure you get the correct type and heat range for your engine (likely a 4.0L straight-6 or a 4.7L V8). Check your owner's manual or a parts store using your VIN for the exact specifications. Champion, NGK, and Autolite are reputable brands.
* Spark Plug Socket: A deep well socket that fits your spark plugs (likely 5/8" or 13/16", check your plugs' size). Get a good quality socket to avoid rounding off the plugs. A magnetic spark plug socket is highly recommended to prevent dropped plugs from falling into the engine.
* Wrench: A ratchet with an extension will be very helpful to reach the plugs. A swivel head ratchet is also a good investment for this job.
* Spark Plug Wire Puller (optional but highly recommended): This tool makes removing and installing the spark plug wires much easier and reduces the risk of damage.
* Gloves: To protect your hands.
* Penetrating Oil (like PB Blaster): This can help loosen stuck spark plugs. Apply it several hours before starting the job.
* Shop Rags or Paper Towels: For cleaning.
* Owner's Manual: Consult this for torque specifications for your spark plugs and any specific instructions.
Procedure:
1. Safety First: Disconnect the negative terminal of your battery to prevent electrical shock.
2. Access: Locate the spark plugs. On a 4.0L, they're generally on the top of the engine, though accessing some may require removing parts like the air intake or other components. The 4.7L's location is similar but might require even more maneuvering. Consult a repair manual specific to your engine for detailed access instructions.
3. Remove Spark Plug Wires: Carefully disconnect the spark plug wires one at a time. Using a spark plug wire puller is highly recommended to prevent damage to the wires or the spark plug boots. Note the order of the wires if you're unsure, or take pictures before disconnecting.
4. Loosen Spark Plugs: Spray penetrating oil on the spark plugs if they're difficult to remove. Using the proper socket and ratchet, carefully loosen each spark plug. Don't force it – if it's stuck, apply more penetrating oil and let it sit for a while.
5. Remove Spark Plugs: Once loosened, carefully remove each spark plug by hand, using the magnetic spark plug socket to avoid dropping it into the engine.
6. Inspect Old Spark Plugs: Examine the old spark plugs for wear and tear. This can help diagnose potential engine problems.
7. Install New Spark Plugs: Carefully screw in the new spark plugs by hand until they are snug. Then use the ratchet to tighten them to the manufacturer's recommended torque specification (found in your owner's manual or a repair manual). Do not overtighten!
8. Reconnect Spark Plug Wires: Attach the spark plug wires back to the new spark plugs, ensuring a secure connection.
9. Reconnect Battery: Reconnect the negative battery terminal.
10. Start the Engine: Start the engine and check for any misfires or other problems.
Important Considerations:
* Repair Manual: A repair manual specific to your 1998 Jeep Grand Cherokee Limited is highly recommended. It will provide detailed diagrams, torque specifications, and other crucial information to make the job easier and safer. You can find these online or at auto parts stores.
* Difficult Access: Be prepared for some tight spaces and potentially difficult access to some spark plugs. Patience and the right tools are key.
* Torque Specifications: Using the correct torque is critical to prevent damaging the spark plugs or the engine. Over-tightening is a common mistake that can lead to stripped threads or cracked spark plugs.
If you're not comfortable performing this repair yourself, it's best to take your Jeep to a qualified mechanic. This is not a beginner-level job, and incorrect procedures can lead to engine damage.
