🔧 Supra - Spark Plug Replacement

On your Supra, replacing the spark plugs restores smooth idle, strong acceleration, and helps prevent misfires under boost. This job is done from the top of the engine by removing the ignition coils and swapping the plugs one-by-one.

Difficulty Level: Intermediate | Estimated Time: 1.0-2.0 hours

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⚠️ Safety & Precautions

• ⚠️ Do this on a fully cool engine to avoid burns and to protect the aluminum cylinder head threads.
• ⚠️ Keep dirt out of the spark plug holes—debris can damage the engine.
• ⚠️ Do not use anti-seize on these plugs unless the plug maker specifically requires it (most modern plugs are nickel-plated and are installed dry).
• ⚠️ Ignition OFF, key away from the car while connectors are unplugged.

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🔧 Required Tools

You'll need the following tools for this repair:

• 8mm socket
• 10mm socket
• 3/8" drive ratchet
• 3/8" drive torque wrench (10–60 Nm range)
• 3/8" drive extension set (3", 6")
• 14mm 12-point thin-wall spark plug socket (magnetic or rubber insert)
• Trim clip removal tool
• Pick tool
• Compressed air blow gun
• Shop vacuum
• Flashlight
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (OEM-equivalent for Supra 3.0) - Qty: 6
• Ignition coil boot set - Qty: 6 Optional if boots are torn/oil-soaked

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📋 Before You Begin

• Park on level ground, set the parking brake, and let the engine cool completely.
• Open the hood and remove any loose items so nothing falls into the engine bay.
• Use shop vacuum to clean dust/leaves around the top of the engine before you open anything.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Use your hands to pull straight up on the engine cover to release the rubber grommets.
• Set the cover aside where it won’t get stepped on.

Step 2: Access the ignition coils

• Use a flashlight to locate the 6 ignition coils on top of the valve cover.
• If any small harness retainers/clips are in the way, release them with a trim clip removal tool (a pry tool that pops plastic clips without breaking them).

Step 3: Unplug each ignition coil connector

• Work one cylinder at a time so nothing gets mixed up.
• Use a pick tool to gently help lift the connector lock if it’s tight (do not force it).
• Pull the connector straight off the coil.

Step 4: Remove the ignition coils

• Pull the coil straight upward while wiggling gently.
• Tip: Twist slightly to break the seal.
• Set the coil aside in order.

Step 5: Clean the spark plug wells

• Use compressed air blow gun to blow out debris around each spark plug hole.
• If you see loose dirt, use a shop vacuum to remove it first.

Step 6: Remove the old spark plug

• Install the 14mm 12-point thin-wall spark plug socket on a 3/8" drive extension and 3/8" drive ratchet.
• Turn counterclockwise to loosen, then remove the plug straight out.
• Inspect the plug tip for heavy deposits or oil.

Step 7: Install the new spark plug (start by hand)

• Put the new plug into the 14mm 12-point thin-wall spark plug socket so it won’t drop.
• Thread it in by hand using only the extension (no ratchet at first) until it seats smoothly.
• Tip: If it doesn’t spin easily, back out and retry.

Step 8: Torque the new spark plug

• Use a 3/8" drive torque wrench (10–60 Nm range) (a tool that tightens to an exact setting so you don’t strip threads).
• Tighten the plug to Torque to 23 Nm (17 ft-lbs).

Step 9: Reinstall the ignition coil

• Push the coil straight down onto the plug until fully seated.
• Reconnect the coil electrical connector until it clicks/locks in place.

Step 10: Repeat for all cylinders and reassemble

• Repeat Steps 3–9 for the remaining 5 spark plugs.
• Reinstall any harness clips you removed using the trim clip removal tool.
• Press the engine cover back on until all grommets snap into place.

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✅ After Repair

• Start the engine and let it idle for 30–60 seconds. It should run smooth with no flashing check-engine light.
• Take a short test drive and check for hesitation under light acceleration.
• If you get a misfire/check-engine light, recheck each coil connector is fully seated.

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💰 DIY vs Shop Cost

Shop Cost: $450-$900 (parts + labor)

DIY Cost: $90-$220 (parts only)

You Save: $360-$680 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.0-2.0 hours.

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🎯 Ready to get started?

HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.