Randy McCoy Jr.
Randy McCoy Jr.




How to change coil pack and spark plugs.

DTC: P0304

Estimated Time:

0.75 - Repair

0.50 - Diagnostic

Tools Required

  • T-30 torx bit
  • 5/8 spark plug socket
  • 3/8 drive extension
  • 3/8 ratchet
  • spark plug gapping tool

Parts Required

  • spark plugs
  • coil pack


INTRO: For this job, the customer stated that the vehicle would jump and not accelerate. Road testing the vehicle shows that the engine will not rise over 2,000 RPM. A DTC shows to be P0304 (cylinder 4 misfire).

DIAGNOSTIC: Removing the cylinder 4 coil pack shows that the coil pack was broken. In this case, the coil pack was duct taped at some point by someone else. The duct tape did not hold the coil pack together and is not recommended for repairing a coil. Bad coils should be replaced with a new coil pack.

REPAIR (Removal): Remove the cover on the top of the engine. This can be done by pulling upward on it. There are rubber bushings holding this on. Removing this exposes all four coil packs. To remove the coil pack, use a T-30 torx bit to remove the retaining bolt holding down the coil pack. Remove the electrical connector on the coil pack. Now you can pull the coil out of the hole. All four coil packs have the same process for removing them. Once coils are removed, use a 5/8 spark plug socket to remove the spark plugs in the hole that the coils came out of. An extension and a ratchet will be necessary for getting down inside of the hole. If you do not have a spark plug socket to hold the spark plug, use a magnet to retrieve the spark plug from the hole. It is recommended to replace all spark plugs when replacing a coil. It is good to maintain the spark plugs for power and fuel efficiency.

REPAIR (Installation): Before installing the new spark plugs, make sure to use a spark plug gapping tool to gap the plugs to 0.044. After this, the spark plugs are ready to be installed. This can be done using the spark plug socket. Anti-seize can be used on the treads if desired. If this is not available to you, drop the socket down the hole and use a deep well 5/8 socket to start the spark plug into the cylinder head. Tighten the spark plugs until they are snug. Do not over tighten and strip the threads!!! Install the coil packs by pushing them down onto the spark plugs. Connect the electrical connector to the coil packs in the same orientation they were taken off. Install the retaining bolt with the T-30 torx bit. Reinstall the engine cover by lining up the rubber bushings with the mounts and press down to secure the bushing to the mounts. This completes the install.

TIPS: To test a bad coil, swap the suspected bad coil with a suspected good coil. In this case, coil 4 was suspected to be bad. Coil 4 and coil 2 can be swapped. After swapping the coils, have the DTC (check engine light) be erased. This can be done at most local auto part stores. Drive the vehicle until the computer goes through the drive cycle and turns the check engine light back on. Have the codes read again. If the DTC says the misfire is on cylinder 2, then the coil is the bad part because the problem followed the coil. If the DTC still says cylinder 4 misfire (or whatever cylinder had the misfire originally) then the problem is not the coil. The problem could be in the wiring going to the coil or it could be the spark plug. 2013 JEEP PATRIOT 4 CYLINDER SPARK PLUG AND COIL PACK REPLACEMENT-4ff6 #1-

This is one way to quickly and easily test a coil pack.