Six wires plus coil wire. Mopar OE or NGK/Bosch quality; cheap parts-store sets cause crossfire and rough idle.
Plug wires on the 4.0L deteriorate from heat radiating off the exhaust manifold (which runs directly below them). Symptoms of failure include rough idle, P0300 random misfires, hesitation under load, and visible arcing in the dark. Always use a Mopar, NGK, or other quality 8mm spiral-core set; the cheapest parts-store wires (often Standard or Echlin) frequently fail within a year and cause crossfire between adjacent cylinders. Firing order is 1-5-3-6-2-4 with cylinder 1 at the front. Mark the distributor cap rotation and replace one wire at a time to avoid swaps. Route wires in the OEM looms and away from the exhaust manifold; this is critical because a wire touching the manifold burns through in weeks. Renix-era (1987-1990) and HO (1991-2001) share the same routing.
| Part | Vendor | Est. price |
|---|---|---|
| Mopar plug wire set | Mopar | ~$75 |
| NGK wire set alternative | RockAuto | ~$45 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.