On the 4.0L 6-cylinder engine, the spark plugs are located below the coil rail assembly. This coil rail assembly contains three individual coils with the bottom containing 6 rubber spark plug boots to seal the 6 spark plugs to the coil assembly. Inside each rubber boot is a spring that is used for an electrical contact between the coil and the top of the spark plug. These rubber boots and springs are a permanent part of the coil assembly and are not to be serviced separately.

  1. Disconnect the negative battery cable at the battery.
  2. The coil is mounted directly to the cylinder head. Remove 4 coil mounting bolts.
  3. Carefully pry up the coil assembly from the spark plugs. Do this by prying alternately at each end of the coil until the rubber boots have disengaged from all spark plugs. If the boots will not separate from the plugs, use a commercially available spark plug removal tool. Twist and looosen a few boots from a few spark pugs to help remove the coils.
  4. After coil has cleared spark plugs, position coil for access to primary electrical connector at the rear of the coil assembly. Disconnect the connector from the coil by pushing the slide tab outwards to the right side of the vehicle. After slide tab has been positioned outwards, push in on the secondard release lock on the side of the connector and pull the connector from the coil.
  5. Remove the coil assembly from the vehicle.
  6. Prior to removing the spark plugs, blow compressed air (if available) around the spark plug. This will helpprevent foreign material from entering the combustion chamber.
  7. Remove the spark plugs from the cylider head with a quality socket equipped with a rubber or foam insert. Inpsect spark plug condition. Click on charts below to identify the condition of your plugs. Take corrective action if necessary.


Special care must be taken when installing spark plugs into cylinder head spark plug wells. Be sure plugs do not drop in plug wells as ground straps on the plugs may be bent resulting in change in the plug gap, or electrodes can be damaged.

Always tighten spark plugs to specified torque. Over tightening can cause distortion resulting in a change in spark plug gapp or a cracked porcelain insulator.

  1. Use Mopar spark plugs #RC12ECC.
  2. Gap plugs to .035 with a spark plug gap gauge.
  3. Start spark plug into cylinder head by hand to avoid cross-threading.
  4. Tighten spark plugs to 26-30 Ft. lbs.
  5. Reinstall ignition coil assembly. Torque mounting bolts to 250 In. Lbs. (not Ft. Lbs.)
  6. Reattach coil assembly primary electrical connector.
  7. Reattach battery cable.

Help the Cause

Did this site help you?   Did it save you some money?   Show your gratitude by helping to keep it online!

Use the donate button below to make a contribution via Paypal.

Thank you to those who have made donations - your generosity is greatly appreciated.

Login Form

To access our downloads, please login. If you haven't created a free account yet, please create an account.

Shop Spark Plugs/Wires

Jeep®, Jeep® Grand Cherokee, Jeep® Cherokee, Jeep® Wrangler, Jeep® Liberty, Jeep® Commander, Jeep® Commanche, Jeep® Compass, Jeep® Patriot, Jeep® Renegade, Jeep® Rubicon, Jeep® Wagoneer, Jeep® Gladiator, Jeep® Cherokee Chief, the Jeep® grille, Quadra-Drive, Quadra-Trac II, Selec-Trac, Vari-Lok, Trac-Lok, Quadra-Coil, Sentry Key, and Mopar are trademarks of FCA US LLC.