🔧 Ascent - Spark Plug Replacement

On your Ascent, the spark plugs sit on the sides of the flat (boxer) engine, so access is tight but doable with the right socket and extensions. Replacing worn plugs helps prevent misfires, rough idle, and poor fuel economy, and keeps the turbo engine running smoothly.

Difficulty Level: Intermediate | Estimated Time: 1.5-3.0 hours

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⚠️ Safety & Precautions

• ⚠️ Work on a fully cool engine; the turbo area gets extremely hot.
• ⚠️ Disconnect the negative battery terminal to prevent accidental shorts.
• ⚠️ Do not pull on wiring; always pull on the connector body.
• ⚠️ Keep dirt out of the plug wells; blow them out before removing plugs.
• ⚠️ Don’t use anti-seize on modern plated spark plugs unless the plug maker specifically requires it.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 10mm socket
• 3/8" ratchet
• 3/8" torque wrench (10-30 ft-lbs range)
• 3/8" extension set (3", 6", 10")
• 3/8" universal joint swivel
• 14mm thin-wall spark plug socket (magnetic or rubber insert)
• Flathead screwdriver
• Needle-nose pliers
• Trim clip removal tool
• Compressed air blow gun
• Feeler gauge set (wire type)
• Dielectric grease
• Flashlight

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs (OEM-equivalent spec) - Qty: 4
• Throttle body gasket - Qty: 1 (only if you remove throttle body for access)

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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 completely (at least 1 hour after driving).
• Use a 10mm socket to disconnect the negative battery terminal and move it aside so it can’t spring back.
• Plan to replace plugs one cylinder at a time so connectors and coils don’t get mixed up.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover and open up working room

• Pull up to remove the engine cover (it’s held by rubber grommets).
• Loosen intake duct/hose clamps using a flathead screwdriver.
• Remove any intake ducting/airbox snorkel pieces that block access using a 10mm socket and trim clip removal tool.
• Take a quick photo before removing hoses.

Step 2: Access the ignition coils (one side at a time)

• Locate the ignition coils on the left and right sides of the engine (one coil per cylinder).
• Press the connector tab and unplug the coil connector by hand (use needle-nose pliers only if needed, gently).
• Remove the coil hold-down bolt using a 10mm socket.
• Twist the coil slightly, then pull it straight out.
• Torque to 8 Nm (6 ft-lbs) when reinstalling the coil bolt.
• If it feels stuck, twist—don’t pry hard.

Step 3: Clean the spark plug well

• Use a compressed air blow gun to blow out dirt/debris from the spark plug well.
• This prevents grit from falling into the cylinder when the plug comes out.

Step 4: Remove the old spark plug

• Install the 14mm thin-wall spark plug socket on a 3/8" extension and 3/8" ratchet.
• Use the 3/8" universal joint swivel if the angle is tight.
• Break the plug loose, then unscrew it the rest of the way and lift it out with the spark plug socket.
• If it feels abnormally tight the whole way out, stop and work it back-and-forth gently to avoid thread damage.

Step 5: Check and prep the new spark plug

• Check the plug gap using a feeler gauge set (wire type) and confirm it matches the plug manufacturer spec for your Ascent.
• Do not force-bend fine-wire iridium electrodes; if the gap is off, exchange the plug.
• Apply a small amount of dielectric grease inside the ignition coil boot (dielectric grease is a non-conductive grease that helps prevent moisture and makes future removal easier).

Step 6: Install the new spark plug (prevent cross-threading)

• Place the new plug into the 14mm thin-wall spark plug socket.
• Thread it in by hand first: use only the extension with your fingers (no ratchet yet) until it seats smoothly.
• Set your 3/8" torque wrench and tighten the spark plug to 21 Nm (15.5 ft-lbs).

Step 7: Reinstall the ignition coil

• Push the coil straight onto the plug until fully seated.
• Install the coil bolt using a 10mm socket, then tighten to 8 Nm (6 ft-lbs) using the torque wrench.
• Reconnect the coil electrical connector until it clicks.

Step 8: Repeat for the remaining 3 cylinders

• Move to the next cylinder and repeat Steps 2–7 until all 4 plugs are replaced.
• Do one plug at a time to avoid mix-ups.

Step 9: Reinstall intake parts and reconnect the battery

• Reinstall all intake ducting/clips using the 10mm socket and trim clip removal tool.
• Tighten hose clamps using a flathead screwdriver.
• Reconnect the negative battery terminal using a 10mm socket (snug, do not over-tighten).
• Reinstall the engine cover by pressing it down into its grommets.

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✅ After Repair

• Start the engine and let it idle for 1–2 minutes.
• Listen/feel for a smooth idle—no shaking or sputtering.
• If you have a check-engine light or misfire after the job, re-check that every coil connector is fully clicked in and every coil is fully seated.
• Take a short test drive, then re-check that intake clamps are tight (no hissing/air leak sound).

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💰 DIY vs Shop Cost

Shop Cost: $350-$650 (parts + labor)

DIY Cost: $60-$180 (parts only)

You Save: $170-$590 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-3.0 hours.

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🎯 Ready to get started?

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