2018 Jeep Cherokee — Spark Plug Type, Gap & Torque

Quick reference

Note: FCA/Mopar sources plugs from suppliers like NGK or Champion. Part numbers vary by build date and emissions family; always confirm by VIN to avoid heat-range or reach errors. Do not re-gap fine-wire iridium/platinum more than a slight correction.

Why the right plug matters

• Heat range: The plug’s ability to shed heat must match the engine. Too hot risks pre-ignition; too cold fouls easily. The Tigershark and Pentastar each require a specific heat range—use VIN-correct parts.
• Electrode material:
  • Iridium: Longest life and most stable spark. OE-style for most late FCA applications, with ~100k-mile service life.
  • Platinum: Middle ground for cost and longevity (~60k miles). Acceptable if it meets OE spec and heat range.
  • Copper/Nickel: Great conductor but short life (~30k miles). Not recommended unless specifically called for by service info.
• Thread reach and seat: Using an incorrect reach can damage the piston or leave threads exposed to carbon. Seat style (taper vs. gasket) also dictates torque—match OE exactly.

How to gap a spark plug

1. Verify the spec: Check the under-hood emissions/tune-up label or FCA service info. Most 2018 Cherokees specify ~0.043 in (1.10 mm).
2. Use a wire-style gap gauge: Slide the ground strap over the correct wire size to verify.
3. Adjust carefully: If a slight correction is needed, bend only the ground strap with a dedicated tool. Do not pry on the iridium/platinum center electrode.
4. Re-check: Confirm uniform gap and that the ground strap is centered over the center electrode.

Replacement procedure tips (2018 Cherokee specifics)

Both engines use coil-on-plug (no distributor).

General setup

• Work on a cool engine. Remove the negative battery cable if you’ll be moving the intake plenum (3.2L).
• Blow out debris around plugs to prevent dirt from entering cylinders.

2.4L I4 Tigershark

• Coil removal: Unplug the coil connectors, remove the 10 mm coil hold-down bolts, and pull coils straight up.
• Plug removal: Use a 5/8 in spark plug socket with extension. Break free, then back out by hand. If resistance increases, thread in slightly and work back and forth to avoid galling aluminum threads.
• Install: Start new plugs by hand at least 5–6 turns. Torque to about 13 lb-ft (18 Nm) unless service info specifies otherwise. Reinstall coils; apply a pea-sized dab of dielectric grease inside each boot.

3.2L V6 Pentastar

• Access: The front bank is straightforward. The rear bank typically requires removing the upper intake plenum. Label vacuum and EVAP lines and replace the plenum gasket set if flattened or damaged.
• Coil removal: Same as above. Keep coils in order; inspect boots for carbon tracking. Replace any hardened or oil-soaked boots.
• Plug service: Install with a small drop of clean engine oil on threads (or dry if specified). Torque to about 13 lb-ft (18 Nm) unless otherwise specified by FCA.

Anti-seize and dielectric grease

• Anti-seize: Most modern plugs have a nickel-plated shell and do not require anti-seize. Adding it can cause over-torque and thread damage. Only use if the manufacturer explicitly approves; if used, reduce torque by ~20%.
• Dielectric grease: A thin film inside coil boots helps sealing and future removal but keep it off the terminal threads and electrodes.

Final checks

• Clear any diagnostic codes, then road test. A smooth idle and no misfire counts indicate success.

Known issues (what does and doesn’t apply)

• Ford 3-valve 2-piece plug breakage: Not applicable to the 2018 Cherokee.
• GM 5.3L ion-sensing coil quirks: Not applicable.
• Cherokee-specific notes: Misfires are more commonly due to worn plugs beyond interval, hardened coil boots, or vacuum leaks after plenum service on the 3.2L. Ensure the intake plenum and PCV connections are sealed and that coil connectors are fully seated.

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