How to change your vehicle's spark plugs

If you’ve never changed spark plugs before, it probably appears more difficult than it really is. But in reality, changing spark plugs on most vehicles is a relatively easy task requiring few tools and little mechanical experience. Truth be told, this is a job that nearly anyone with basic mechanical skills can do. Follow along as we show you step by step what's involved.

	Things you need:
	New spark plugs that fit your vehicle’s engine
	Consult your owners manual or dealer on correct type. If you don't have an owners manual the correct plug number is usually printed on a sticker in the engine compartment.
	Gap gauge - let's you set the correct gap
	A few tools - Spark plug wrench - generally
	a wratchet wrench and a socket. You may also need extensions and swivels depending on access to your vehicle's plugs.
	Anti-seize lubricant (optional but recommended)
Grease rag or old cloth to wipe hands clean

Never work near an engine when it is warm or hot! Besides the obvious that you might burn yourself, most modern engines use electric cooling fans which can, and often do, come on even after an engine has been shut off. Let the engine cool for an hour before working around it. For added protection remove the negative battery cable.

Basic Steps
1) Locate your engine’s spark plugs.
If you’re not sure where the plugs are, locate the sparkplug wires (long rubbery wires about 1/4” in diameter) and follow them down the side of your motor. If your engine is a 4 cyl. you’ll have 4 wires leading to the spark plugs. If your vehicle has a 6 cyl., look for 3 thick wires on each side of the engine (if it’s a V6). The spark plugs are at the bottom end of each wire.

2) Remove the spark plug wire from the spark plug.
Firmly grab the rubber boot at the bottom end of the spark plug wire and gently pull it away from the spark plug. Make sure you are pulling on the boot of the wire and not the wire itself. If the boot and wire seems to be stuck to the spark plug (which often happens) try firmly twisting the boot side/side to loosen the boot from the spark plug. If you have hard-to-get-at plugs and can barely reach the spark plug wire boot, consider purchasing an inexpensive spark plug wire puller available at most automotive parts stores.

Note: When you are finished changing the plugs, each wire must be reattached to it’s original location. In other words, don't let the wires become mixed up. It's a good idea to either remove one or two plug wires at a time, or mark the wires with a piece of tape and marker to mark their location.

3) Removing each spark plug.
Take your spark plug wrench (socket/ratchet) and carefully loosen each spark plug (turning to the left). It’s a good idea to support the back of the wrench when loosening so as not to ‘push’ or ‘pull’ on the plug as you are turning it. If the plug is hard to get at you may need to use an extension or even a ‘swivel’ to gain better access. Observe the color of the tip of each plug as you remove it. A spark plug can tell you a lot about the condition of your motor. See Spark Plug Tech

4) Prepare new plugs for installation.
Use a gapping tool to properly set the spark plug gap. The “gap” is the distance between the ground electrode (the metal end that sticks out) and the center electrode. To determine what the proper gap should be look in your owners' manual. On most vehicles the gap is also printed on the emissions sticker located in the engine compartment.

Find the thickness on the gapping tool that corresponds to your vehicle’s recommended gap and insert the tool between the two electrodes. If the fit is either very loose or too tight, carefully bend the electrode to the right gap. Never pry the electrodes apart by sticking the tool between the two electrodes - you could damage the inner electrode. Rather, use the slot on the back of the gaping tool to do the bending. Check the gap again and re-bend the electrode as necessary until the tool just fits between the two electrodes. Set the gap for all the new plugs.

5) Apply anti-seize compound on the threads of each plug.
Anti-sieze compound while not absolutely necessary is highly recommended. The idea behind using anti-seize compound is to prevent the spark plug's threads from “sticking” or corroding to the threads of the engine. When this happens the plugs become extremely difficult to remove next time and may even damage the threads on the engine (which would require another repair). It is particularly important with engines with aluminum heads. Don't use grease in place of anti-sieze compound because it won’t withstand the high temperatures.

6) Install new spark plugs.
Carefully install each new spark plug and turn at least 2-3 times by hand (turning right) before tightening the rest of the way with the spark plug wrench. If the plug does not turn in easily by hand, back it out and try again. - you don’t want to accidentally cross-thread the spark plug. Finally, tighten firmly but not excessively tight. If you have access to a torque wrench, consult your manual and tighten to specs.

7) Reinstall spark plug wires
Be sure each spark plug wire is firmly attached to the correct spark plug that it was removed. Push the wire onto the spark plug, until you feel it "click" into place.