🔧 Cherokee - Spark Plug Replacement

On your Cherokee, the spark plugs ignite the air/fuel mix. Worn plugs can cause rough idle, misfires, poor MPG, and hard starts. This job is mostly careful disassembly and reinstalling parts to the correct torque.

Difficulty Level: Intermediate | Estimated Time: 1.5-3 hours

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⚠️ Safety & Precautions

• ⚠️ Work on a cold engine; plugs thread into aluminum and can strip when hot.
• ⚠️ Disconnect the negative battery cable if you’ll be unplugging many connectors near the engine.
• ⚠️ Do not pull on wiring; press the connector lock tab and pull the plastic body.
• ⚠️ Keep dirt out of plug wells; blow debris out before removing any plug.
• ⚠️ Avoid anti-seize on modern plated plugs unless the plug maker requires it.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 10mm socket
• 8mm socket
• 3/8" ratchet
• 3/8" torque wrench (10–30 ft-lbs range)
• 6" socket extension (3/8")
• 12" socket extension (3/8")
• 5/8" spark plug socket
• Trim clip remover
• Small flathead screwdriver
• Feeler gauge set (for spark plug gap)
• Compressed air nozzle
• Flashlight
• Magnetic pickup tool

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (OEM-equivalent iridium) - Qty: 4
• Dielectric grease - Qty: 1

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📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Open the hood and let the engine cool fully (at least 1 hour).
• If disconnecting the battery: use a 10mm socket to remove the negative terminal and isolate it so it can’t spring back.
• Assumption: Spark plugs are accessed from the top after removing the engine cover and intake ducting; some builds may require moving the upper intake/air resonator slightly for clearance.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Grip the cover firmly and pull upward to release the rubber grommets (no tools on most covers).
• Set it aside where it won’t get stepped on.

Step 2: Remove the air intake duct (for working room)

• Use an 8mm socket to loosen the hose clamp(s) on the intake duct.
• Unclip any attached breather/PCV hose using a small flathead screwdriver to gently lift the lock (if equipped).
• Lift the duct out and set it aside.

Step 3: Unplug and remove ignition coils (one cylinder at a time)

• Each cylinder has an ignition coil on top of the plug. (The coil is the pencil-shaped unit that snaps onto the spark plug.)
• Press the electrical connector lock tab and unplug the coil connector.
• Use a 10mm socket with a 6" extension to remove the coil hold-down bolt.
• Twist the coil slightly and pull straight up to remove it. Don’t pry on the plastic.

Step 4: Clean the spark plug well

• Use a compressed air nozzle to blow out dirt around the plug before loosening it.
• Use a flashlight to confirm the well looks clean and dry.

Step 5: Remove the old spark plug

• Install a 5/8" spark plug socket on a 12" extension and 3/8" ratchet.
• Turn counterclockwise to loosen, then spin it out by hand with the ratchet.
• Lift the plug out carefully; use a magnetic pickup tool if it doesn’t come up easily.

Step 6: Check and prep the new spark plug

• Check the gap using a feeler gauge set. Typical gap is around 0.043 in (1.1 mm) on this engine; use the spec provided with the plugs if it differs.
• If the plug is iridium, do not bend the tiny center tip; adjust only if the plug maker says it’s allowed.
• Apply a very small dab of dielectric grease inside the coil boot (this helps prevent moisture/corrosion; it’s non-conductive).

Step 7: Install the new spark plug

• Thread the plug in by hand first using the spark plug socket and extension only (no ratchet) to avoid cross-threading.
• Once finger-tight, use a 3/8" torque wrench to tighten the plug: Torque to 20 Nm (15 ft-lbs).
• If it doesn’t thread easily, stop and realign.

Step 8: Reinstall the ignition coil

• Push the coil straight down until you feel it seat on the plug.
• Install the coil bolt using a 10mm socket, then tighten with a torque wrench: Torque to 9 Nm (80 in-lbs).
• Reconnect the coil electrical connector until it clicks.

Step 9: Repeat for the remaining cylinders

• Repeat Steps 3–8 for the other 3 plugs, working one coil/plug at a time to avoid mixing anything up.

Step 10: Reinstall the intake duct and engine cover

• Reinstall the intake duct and tighten the clamp(s) using an 8mm socket.
• Reconnect any hoses/clips you removed.
• Press the engine cover back onto its grommets.
• If you disconnected the battery, reconnect the negative terminal using a 10mm socket and tighten snugly.

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✅ After Repair

• Start the engine and let it idle for 30–60 seconds; it should be smooth.
• If the check engine light flashes or it runs rough, shut it off and recheck coil connectors and coil seating.
• Take a short test drive and verify normal power and no warning lights.

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💰 DIY vs Shop Cost

Shop Cost: $250-$450 (parts + labor)

DIY Cost: $40-$120 (parts only)

You Save: $210-$330 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-2.5 hours.

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