How to Change Your Spark Plugs

You can fill your engine up with gas, and in fact you really need to from time to time. But without spark plugs, all the gas in the world wouldn’t do you any good. The gasoline in your tanks is injected into your cylinders, where your spark plugs live. In a sequence, each spark plug gives off a small electric shock, creating a small, controlled explosion. These explosions within each cylinder lift each cylinder’s piston, and this motion is harnessed, allowing your car to move. But over time your spark plugs will wear out and offer a much smaller spark, or none at all, wreaking havoc on your gas mileage and performance.

Lucky for you, spark plugs are relatively inexpensive, and easy to replace at home. It takes just about an hour (for a four cylinder vehicle) and will easily save you $100 or more in labor.

You’ll need a ratchet wrench, a 12-inch socket extender, and a spark plug socket (these are often included in your ratchet set – you can also grab one at most hardware stores or auto parts stores).

It’s also important to remember that it’s best to replace all of your spark plugs at the same time. Your “Check Engine” light might go on to tell you that your vehicle is experiencing a “Cylinder 3 Misfire” or something along those lines, but if you’re going to replace number 3, you really should replace them all. Your engine won’t run as well with some old plugs and some new.

And besides, if one has just gone out, chances are the others will soon follow, so you might as well knock this project out in one afternoon, rather than coming back to it later.

First thing’s first, find where your spark plugs are. This is where your owner’s manual comes in handy. On a 4-cylinder engine your spark plugs will usually be on top of or on the side of your engine, lined up in a row. A V6 or V8 engine will probably have them separated evenly on each side of your engine.

Some vehicles will have engine covers that you’ll need to remove to see the spark plug wires, which you’ll then have to trace back to find the plugs themselves. Again, check your manual. There you can also double check how many you have, what size of socket you should use, and how they are numbered.

Once you’ve located your first plug, gently pull the wire plug from the engine. Don’t yank it – grip it firmly, as close to the engine as possible, and slowly work the cable out. This cable is your spark plug lead and being too forceful with it could ruin it. And that will be a harder repair, don’t do it to yourself. Keep in mind it’s best to go one at a time. That is – remove and replace one spark plug, before moving on to the next. Otherwise you’ll end up with all 4-8 of your spark plug leads dangling around, and you might not remember where each one attaches – having your spark plugs fire off in the right order is imperative, so why risk incorrectly rewiring them?

If you simply must remove them all at once, grab some masking tape and number each one as you go.

Put your extension and socket onto your ratchet, and go fishing! When you get your socket over the old plug, you can loosen it up and pull it right out. This socket is designed to do this easily, in fact many are magnetic. But if your old plug doesn’t want to get pulled out, try spraying some compressed air in there to clean it off a little.

Go ahead and take a look at the old one once you get it out. Hopefully it has a little bit of soot on the end. If it looks oily or white on the end you might have some more serious problems with your engine’s cooling or ignition timing.

Your manual will tell you which ones you want. It’s best not to try to save a few bucks here by opting for a cheaper version – your manufacturer chose the right ones for a reason.

Place your spark plug in your socket and carefully guide it in to place. It’s not hard to break or bend these, so you want to be gentle, even going so far as to tighten it by hand at first (using your hand on the extender). Once you’ve got it in place you can switch back to the ratchet to tighten it further.

It’s important to note: you want it tight, but not too tight. Excessive torque is not the goal here, and in fact that could be damaging to your new plug. But, when it feels like it’s in place and not going anywhere, put your spark plug lead back in place, make sure the edges are sealed and that’s it!

One down, 3-7 to go. Just repeat these steps on the remaining plugs and you’ll be ready to go. Fire up that engine and enjoy a smoother ride, better gas mileage, and an all-around healthier machine.