DIY Network

Tricked Out WEB EXTRA: How to Change and Gap Spark Plugs A quick-and-dirty guide to the proper care and feeding of spark plugs. From "Tricked Out" episode DTRK-305

Changing spark plugs isn't rocket science, but it is something that--if done improperly--will not only compromise your engine performance, but can also cause damage. Here are some basic things you need to know.

First, be sure you let the engine cool fully before changing the spark plugs.

Tip: It's recommended that you change one spark plug at a time, putting the wire back on after you're done. If you pull all the wires off at once, you may put them back on the wrong spark plugs; this changes the firing order, and your car will run poorly or not at all. If you need to remove all the wires use tape and mark each wire and its location.

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Removing Your Spark Plugs

• Change one spark plug at a time, putting the plug wire back on before changing the next spark plug.

• Pull the spark plug wire where it attaches to the plug grabbing the rubber boot at the end of the wire. Pulling higher up on the wire can damage the spark plug wire and cause it to separate.

• Clear away any dirt or debris around the spark plug. This will help in preventing anything from falling down into the engine.

• With a spark plug socket and ratchet, remove the spark plug by turning it in a counterclockwise direction. You may need an extension for your ratchet if the spark plugs are deep-set or not directly accessible.

Gapping Your Spark Plugs

• Find the chart listing the proper "gap" for your plugs in your car's repair manual. The information may also be on the sticker on the inside of the car's hood. The parts store can provide you with this specification as well.

• Insert the spark plug gapping tool in the gap between the metal center electrode and the metal side electrode of the plug's tip.

• Look at the tool's ruled edge and find the gap's measurement. If it is too big, bend the spark plug's end with the tool to widen the gap. To make the gap smaller, push the side electrode against a hard service.

• After adjusting, measure again. Repeat this procedure until the gap matches the specification.

• Repeat with each plug.

Note: Spark plug gap specifications are listed in inches and/or millimeters. The gapping tool will have inches on one side and millimeters on the other.

Important: Make sure you buy the right spark plugs for your car based on its model, make and year.

Installing The Spark Plugs

• Before installing the spark plug apply a small amount of anti-seize lubricant to the spark plug threads. This will prevent corrosion and seizing and will assure easier disassembly.

• Hand-tighten each spark plug. If you feel any resistance, stop and start over to prevent cross-threading.

• Tighten the plugs with a socket wrench until snug. Do not over-tighten.

• When replacing the spark plug wires coat the inside of the boot with a generous amount of boot release (silicone grease available at your auto parts store). This will make it easier to remove the boot next time. Usually, you will hear a soft pop when the plug wire snaps onto the plug.

• Start the engine. Listen. If the engine runs roughly or doesn't start, make sure the wires are pushed all the way onto the new plugs.