Although many manufacturers are setting spark plug maintenance intervals near 100,000 miles, most enthusiast prefer to swap spark plugs more regularly. With spark plugs being relatively inexpensive, there are absolutely no downsides to replacing them as part of your regular maintenance regimen.By Joseph Coelho – November 17, 2015
Contributors: JeepFan & DSJeeps.

This article applies to the JK Jeep Wrangler (2007-Present).

Spark plugs are key components of any gasoline internal combustion engine. These small devices deliver electric current from the ignition coil(s) to ignite the air/fuel mixture inside of the combustion chambers. While spark plugs have proven to be quite robust and can last thousands of miles without the need for replacement, modern ignition systems have become quite sensitive to worn spark plugs. As spark plugs age, material from the electrode erodes and creates a larger gap for the voltage to jump across. Excessive gap has a tendency to place a strain on plug wires and ignition coils because this larger gap creates a higher resistance that must be overcome to create a spark. Spark plugs can also experience carbon buildup or insulator cracking, all of which can lead to engine misfiring or premature coil failure. Proper spark plug maintenance will ensure your ignition system is performing at its best to maximize combustion efficiency. This article will outline the procedure for replacing spark plugs in 2007 to present JK Jeep Wrangler models.

Materials Needed

  • 1/4″ and 3/8″ drive ratchets
  • 5/8″ spark plug socket
  • Various extensions (with one being at least 12″ long)
  • 8mm and 10mm sockets
  • T20 Torx driver
  • Torque wrench
  • Universal joint (swivel adapter)
  • Spark plug gapping tool or feeler gauges
  • Screwdriver
  • Dielectric grease
  • Anti-seize paste (optional)

Buying Replacement Spark Plugs

Generally, it is best to use OEM equivalent spark plugs in your Jeep. Aftermarket spark plugs can be less expensive, but they are often not made to the exacting standards as the spark plugs fitted from the factory. OEM plugs usually have a specific electrode design and material quality that is best suited for the engine. This is not to say there are no exceptions to this rule, but more often than not, individuals experience various engine and ignition system problems by using “exotic” aftermarket spark plugs instead of the tried and true originals.

  • 2007-2011: Champion Part #RE14PLP5
  • 2012+: Champion Part #RER8ZWYCB4

Figure 1. Quality spark plugs.

This how-to will cover spark plug replacement for both 2007 to 2011 3.8L EGH V6 engine and 2012+ 3.6L Pentastar V6 engine. For 2012+ models, the step-by-step instructions are below.

2007-2011 3.8L EGH V6 Engine

Step 1 – Replace bank 2 spark plugs

The 2007 to 2011 Wranglers equipped with the older 3.8L V6 engine allows for easy access to the driver’s side spark plugs.

  • Locate the three spark plug wires on the driver’s side of the engine. With a twisting motion, remove each spark plug wire from its companion spark plug. The spark plug wires are typically numbered to prevent them from getting mixed
  • Using a 3/8″ drive ratchet with an extension, universal joint adapter, and 5/8″ spark plug socket, remove the spark plugs.
  • Figure 3. A long extension and universal joint allows for easy reach of the spark plugs.
  • With the old spark plugs removed, prep the new spark plugs by checking the electrode gap with a gapping tool or feeler gauge. The spark plug gap specification for 2007 to 2011 models is .050″. Do not assume the plugs are ready to run out of the box. Improper spark plug gap can lead to rough running conditions.Figure 4. Checking and adjusting spark plug gap.
  • Place the new spark plug into the spark plug socket, making sure it is firmly held in place, and then lower it into its respective position in the cylinder head. Thread the spark plug carefully into the cylinder head and tighten it to 12 ft/lbs. Repeat for each plug.

  • Figure 5. A 3/8″ drive torque wrench can be used to tighten spark plugs.

Pro Tip

While Jeep does not suggest anti-seize paste on the threads of the spark plugs, some individuals opt to apply it, especially if your Jeep is used for off-road purposes.

  • Apply a thin film of dielectric grease to the spark plug boots before installing them onto the spark plugs. A small “click” can be heard and felt when the spark plug boot is firmly seated on the spark plug.

Step 2 – Replace bank 1 spark plugs

To gain access to the passenger’s side spark plugs, a few components must first be moved.

  • Disconnect the bank 1 spark plug wires (1, 3, 5) from the coil pack. It is recommended you label them if your wires are not already labeled.
  • Remove the spark plug wires from the passenger’s side spark plugs and remove the heater hose retaining strap from the valve cover. Also, remove the vent hose from the valve cover.
  • Remove the plastic spark plug wire tray from its mounting point on the valve cover. Maneuver the spark plug wires out from behind the engine and remove them from the engine bay. Pay close attention to their routing, as it will allow for proper installation after the new spark plugs are installed.