How To Change Spark Plugs in Jeep Cars

by Contributing Writer

Plugs become cold-fouled -- often referred to as carbon-fouled. This usually happens if one or more of the wires are defective, if the air cleaner element is clogged or you drive only short distances. Leaking valve guide seals, worn piston rings and cylinder wear also foul plugs. Over time, the gap gets bigger on the electrodes -- this is normal wear and tear, but the plugs must be replaced to ensure proper running conditions.

Under The Hood:

 How To Change Spark Plugs in a 2007 Jeep Compass

Check the gap between the ground and center electrodes on all four new spark plugs, using a spark plug gap tool. The specified gap for the 2.0-liter and 2.4-liter engine is 0.038 to 0.043 inches. If the gap is wider and narrower than the specified amount, adjust the gap using the spark plug gap tool. Do not attempt to adjust the gap on platinum or double platinum spark plugs.

Grab the front of the plastic engine cover, on both corners, and pull it upward to disengage the clips holding it in place. Grab both corners of the rear part of the engine cover and pull it up until the clips disengage. Remove the cover from the engine and set it in a secure location.

Unplug the wiring harness from the top of the ignition coil pack, by pressing the locking button and pulling the harness from the coil pack. Remove the coil pack securing bolt, using a ratchet and a Torx-bit socket. Remove the coil, by pulling it upward with a slight twisting motion.

Remove the spark plug from the engine using a ratchet, 6-inch extension and a spark plug socket. Pull the spark plug from the socket and insert a new spark plug in the spark plug socket until the rubber insert grips it firmly.

Hand-tighten the spark plug into the engine, using a spark plug socket and 6-inch extension. Attach a torque wrench to the 6-inch extension and spark plug socket, and apply 20 foot-pounds of torque to the spark plug.

Reinstall the coil pack on the spark plug and press it downward until it "clicks" into place on the spark plug. Tighten the coil pack bolt to 6 to 7 foot-pounds, using a torque wrench and a Torx-bit socket. Reconnect the wiring harness onto the coil pack.

Repeat Steps 3 through 6 for all four spark plugs.

Reinstall the plastic engine cover and press all four corners down to lock the clips in place.

Items you will need

  • Four new spark plugs

  • Spark plug gap tool

  • Ratchet

  • Torx-bit socket set

  • 6-inch extension

  • Spark plug socket

 How to Change the Spark Plugs for a 1998 Jeep Wrangler TJ

The 4.0-Liter Engine

Check the gap between the center and ground electrodes on all six new Champion RC-12LYC, or equivalent spark plugs, using a spark plug gap tool. The correct gap for the 4.0-liter's spark plugs is 0.033 to 0.037 inches. Use the spark plug gap tool to make the gap wider or narrower, as needed.

Find the coil rail assembly on the top center of the engine's valve cover. Remove the four coil rail-retaining bolts, using a ratchet and socket. Pry upward on the coil rail, using a 12-inch pry bar, to free it from the spark plugs. Slide the locking tab on the wiring harness -- on the rear of the coil rail -- toward the passenger's side of the Wrangler to unlock it. Press the locking button on the coil rail wiring harness and pull the harness away from the coil rail. Pull the coil rail off the top of the engine, exposing the spark plugs below it, and place it in a secure location.

Remove one spark plug, using a ratchet, 6-inch extension and a spark plug socket. Pull the spark plug from the spark plug socket and push a new plug into the socket until the socket's rubber insert holds the plug in place.

Hand-tighten the spark plug into the engine, using a 6-inch extension and spark plug socket. Connect a torque wrench to the 6-inch extension and tighten the spark plug from 26 to 30 foot-pounds.

Repeat Steps 3 and 4 to replace the remaining five spark plugs.

Plug the wiring harness back into the receptacle on the rear of the coil rail. Slide the locking tab toward the engine to lock the harness into place. Line the coil rail boots up with the tops of all six spark plugs and press the coil rail downward until it seats on the spark plugs. Tighten the coil rail-retaining bolts from 20 to 21 foot-pounds, using a torque wrench and socket.

The 2.5-Liter Engine

Check the gap on the base of all four new Champion RC-12LYC, or equivalent spark plugs, using a spark plug gap tool. The prescribed gap on the 2.5-liter engine is 0.033 to 0.037 inches. Adjust the gap on any incorrectly gapped spark plugs by widening or narrowing the gap with a spark plug gap tool.

Trace a spark plug wire until you reach where the thick rubber boot connects the wire to the spark plugs. Grab the rubber boot and pull upward with a slight twisting motion to remove the spark plug wire.

Inspect the spark plug wire for any visual defects, including cracking, splitting, burning or brittleness. If any defects exist, replace all four spark plug wires one-by-one, as you replace each spark plug. This helps you retain the correct firing order.

Remove the spark plug under where the spark plug wire once was, using a ratchet, 6-inch extension and a spark plug socket. Pull the old spark from the spark plug socket and push a new RC-12LYC , or equivalent spark plug into the socket until the socket's insert holds it in place.

Use the spark plug socket and 6-inch extension to hand-tighten the spark plug into the engine. Attach a torque wrench to the 6-inch extension and tighten the spark plug from 26 to 30 foot-pounds of torque.

Repeat Steps 2 through 5 to replace the remaining three spark plugs in the Wrangler's engine. Replacing the spark plug one-by-one keeps you from mixing up the Wrangler's firing order.

Items you will need

  • 6 new Champion RC-12LYC, or equivalent, spark plugs (4.0-liter)

  • Spark plug gap tool

  • Ratchet

  • Socket set

  • 12-inch pry bar

  • 6-inch extension

  • Spark plug socket

  • Torque wrench

  • 4 new Champion RC-12LYC, or equivalent, spark plugs (2.5-liter)

  • Spark plug wires (optional)

 How to Replace Spark Plugs in a Jeep Patriot

Pop the hood and locate the spark plug wires at the base of the cylinder head, right by the exhaust manifold on the engine. Grab the closest wire to you and pull it off of the plug using a twisting and pulling motion.

Install he spark plug socket onto the ratchet and extension, then unbolt the spark plug from the cylinder head. Pull it out and discard it.

Gap the replacement spark plug using the spark plug gapping tool. Slide the tool between the electrode at the end of the plug and the tip until the gap between the two matches the specifications listed by Jeep in the Patriot's handbook that comes with the vehicle.

Install the replacement plug into the cylinder head, tightening it place using the 3/8-inch ratchet, extension and spark plug socket.

Repeat Steps 2 through 4 for each spark plug on the engine, working one at a time so that you don't confuse the plug wires in the process.

Items you will need

  • 3/8-inch ratchet and extension

  • Spark plug socket

  • Spark plug gapping tool

  • Replacement spark plugs

 How to Replace Spark Plugs on a Jeep Liberty

Adjust the gap on the replacement spark plugs. At the tip of the spark plug that enters the cylinder head is a small metal piece shaped like a hood. The tip of the hook hovers just above a metal circle on the bottom of the spark plug. These two metal pieces are called the electrodes. The distance between these pieces is referred to as a “gap.” The gap determines the length of the spark when the spark plug fires. Before the new plugs can be installed, the gap must be adjusted to .035-inch with a feeler gauge. Select the blade of the feeler gauge which represents .035-inch, then insert the blade between the two metal pieces. Bend the hook-shaped piece toward the plug until the proper gap is reached.

Remove the spark plug wire for any one spark plug. There is no particular order by which the plugs must be replaced. However, it is important to replace only one spark plug at a time to avoid crossing the spark plug wires. Grasp the rubber base of the spark plug wire, where the wire connects to the spark plug, then firmly pull the wire off of the plug. Do not pull the actual spark plug wire, as the wire may pull out of its rubber base. If the wire is stubborn, twist the base of the wire before pulling it off of the spark plug.

Remove the spark plug with either a 10 or 13 mm spark plug socket, depending on the engine, attached to a socket wrench by turning the spark plug in a counterclockwise direction.

Insert a replacement spark plug into the cylinder head, then twist the plug into the cylinder head by hand until it cannot be twisted further with reasonable effort. Tighten the spark plug into the cylinder head with the spark plug socket by 1/4 of a turn. Take care not to over tighten the plug, which may cause the it to break.

Press the rubber base of the spark plug wire onto the top of the replacement spark plug until the wire clicks into place. Follow the same procedure for the remaining spark plugs.

Items you will need

  • Feeler gauge

  • 10 or 13 mm spark plug socket

  • Socket wrench

 How to Replace Spark Plugs on a 2001 Jeep Cherokee

Measure the gap on the new spark plugs with the plug gap gauge and adjust if necessary. Check all of the new plugs at the same time. The proper plug gap is 0.035 inches on four-cylinder and inline-six models, and 0.045 inches on V6 models.

Remove the plug wire from one spark plug by pulling on the boot. Do not pull on the wire.

Remove the spark plug by turning it in a counterclockwise direction with the spark plug socket.

Thread the new plug into the plug hole by turning it clockwise with your fingers. Tighten the plug completely by turning it in a clockwise direction with the spark plug socket. If a torque wrench is available, tighten the plugs on the four-cylinder and inline-six models at 27-foot-pounds and the plugs in the V6 at 22-foot-pounds.

Replace the spark plug wire by pushing the boot back over the plug until it clicks into place. Replace the other plugs in the same manner. Replace one plug at a time to avoid mixing up the plug wires.

Items you will need

  • Spark plug gap gauge

  • Spark plug socket

  • Ratchet

  • Torque wrench (optional)

 How to Replace the Spark Plugs in a 2002 Jeep Grand Cherokee Laredo

Unplug the wiring harness connectors from the coils by pushing downward on the release lock on the top of the connector, then pull the connector off the coil. Unbolt the coils, using the appropriate socket, then pull the coil off the plug.

Blow air around the spark plug, ensuring all debris is removed from the base of the plug, so it doesn't fall into the cylinders.

Remove the spark plug, using the spark plug socket.

Insert the new spark plug, and screw it into the head by hand as far as you can. Tighten the plug firmly, but no more than 28 foot-pounds of torque. The torque wrench is not necessary, as long as you don't over-tighten the plugs.

Reinstall the coil, and tighten the retaining bolt firmly. Plug in the wiring harness connector. Repeat for all plugs.

Items you will need

  • Set of sockets

  • Canned air or air hose/compressor

  • Spark plug socket

  • Torque wrench (foot-pounds, optional)