Symptoms
Misfires, rough idle and lost economy, or simply a truck past the interval. ExtremeTerrain quotes Chrysler's interval as 102,000 miles confirm in manual. ExtremeTerrain suggests pulling one plug for inspection at 60,000 on modified, trail-used trucks.
The fix, step by step
- On the 3.8, pull the wires by the boots.
- On the 3.6, unclip each coil-on-plug connector and remove the coil (typically one 10 mm bolt).
- Gap the new plugs at 0.050 in for the 3.8 (Champion RE14PLP5) or 0.043 in for the 3.6 (Champion RER8ZWYCB4).
- Torque them to 13 lb-ft (±2) on the 3.6.
- ExtremeTerrain gives 12 lb-ft for the 3.8 confirm in manual.
- The Pentastar's 12 mm plugs in aluminum heads don't tolerate over-torquing.
- Add dielectric grease to the boots.
Tools & part numbers
- 5/8 in spark plug socket
- extensions
- 3/8 in torque wrench
- gap gauge
- dielectric grease.
Where to buy the parts
Mopar SP149125AF spark plug, 2012-on 3.6 JKQuadratec ↗Amazon ↗
Crown Automotive S2RE14PLP5 double-platinum plug, 2007–11 JK 3.8Quadratec ↗Amazon ↗
Hunting a used or discontinued part? Search eBay Motors for Jeep Wrangler JK (2-door) parts →
Rated for a competent home mechanic with a decent tool kit. Confirm torque figures, fluids and procedures against the factory service manual for your VIN, support the truck on stands rather than a jack, and work at your own risk (disclaimer). Some parts links are affiliate links, which pay us a small commission at no cost to you.