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EngineMedium

Spark Plug Replacement

Worn spark plugs cause misfires, poor fuel economy, and hard starting. New plugs restore ignition efficiency and smooth engine operation.

Time
1–2 hours
Interval
Every 30,000–100,000 miles
DIY Cost
$20–$80
Shop Cost
$100–$250

Tools & Supplies Needed

Video Guide Coming Soon

Step-by-step video walkthrough for this procedure

Step-by-Step Instructions

1

Gather tools and let the engine cool

You'll need a spark plug socket (5/8" or 13/16" depending on plug type), ratchet, extension, torque wrench, and anti-seize compound. Work on a completely cold engine.

2

Remove the ignition coil or plug wire

Disconnect the electrical connector from the ignition coil. Remove the coil bolt and pull the coil straight up out of the well. On older vehicles, twist and pull the spark plug wire boot.

3

Remove the old spark plug

Use the spark plug socket with an extension to unscrew the plug. If it's very tight, apply penetrating oil and wait 10 minutes. Turn slowly to avoid breaking the plug in the head.

⚠️ Warning: On aluminum heads, only remove plugs when the engine is cold to avoid thread damage.
4

Gap and install the new plug

Check the gap on the new plug with a gap tool — match the spec on the underhood sticker. Apply a tiny amount of anti-seize to the threads. Thread in by hand first, then torque to spec (typically 12–18 ft-lbs).

💡 Pro Tip: Always start spark plugs by hand to prevent cross-threading in the aluminum cylinder head.
5

Reinstall the coil and test

Push the ignition coil back into the well, reinstall the bolt, and reconnect the connector. Repeat for all cylinders. Start the engine and listen for smooth idle.