Replace Your Spark Plugs

01
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Why Do You Need to Change Your Spark Plugs?

Hands holding spark plug
Thinkstock/Stockbyte/Getty Images

Lots of things have changed in recent decades when you talk about the "tune-up." Back when the phrase was coined, you had to get under the hood with screwdrivers and do things like adjust ignition points, replace condensers, set engine timing and change your spark plugs. Wait, we can still change the spark plugs! Most cars still have a spark plug or 8 in there someplace.

The condition of your engine, even your driving habits can affect the life of the plugs. But hey, they're cheap, so replacing them every so often can't be a waste of money. And while you're in there you can inspect your plug wires

Be sure to follow these directions in order, however, because a mix-up can be very confusing to fix.

02
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Get Your Tools Together

This is a special spark plug socket.
Check out the rubber holder inside. Matt Wright

You'll need the following tools to get the spark plug installation done:

  • Ratchet wrench
  • 12-inch socket extension
  • Spark plug socket for your car

It's not too complex, but don't forget to follow the directions in order!

03
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Locate Your Spark Plugs

The view of your spark plug wires from above.
These are 4-cylinder engine plug wires. Matt Wright

Locate the spark plugs. If you follow those thick, rubbery wires under the hood, you'll find the spark plugs (one at the end of each wire.) If you have a 4-cylinder engine, your four spark plugs will be at the top of the engine in a row in front of you. If you have a V8, you'll have to reach down on both sides of the engine to get them out, four on the left and four on the right. If you follow the wires you'll find the plugs.*

*If you follow your spark plug wires, only to discover they lead into an abyss that is unreachable, follow these steps to access the buried spark plugs.

04
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Spark Plug Wire Removal

One wire removed.
Remove your wires one at a time!. Matt Wright

Resist the urge to reach for those spark plug wires and pull them all out at once. Spark plugs fire in a specific order, and it's a lot easier to replace them one at a time without getting them mixed up.

Starting at the end of the row, pull the wire off the end of the spark plug by grasping it as close to the engine as possible then pulling. You might have to give it a little wiggle to get it off. If you have a 4-cylinder engine with the plug wires going into the top, your plugs might be at the bottom of a hole. If this is the case, just pull straight up at the reinforced base and you'll pull a long rubber boot out of the hole.

05
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Removing the Spark Plug

A spark plug in special socket.
The socket will hold onto the spark plug. Matt Wright

Now that you have one plug wire off, put your spark plug socket and the extension on your ratchet. If you look inside the spark plug socket, you should see some black foam or rubber on the inside end. This is important because it holds onto the spark plug while you maneuver it in and out of the engine.

If for some reason your socket doesn't have the gripper in there, you can improvise. Cut off a half inch or less of electrical or masking tape and stick it onto the inside of the clean socket. This will make the socket grip a little more tightly on the spark plug so you can hold onto it.

With your ratchet wrench set to loosen (that's counter-clockwise) slide it over the end of the plug, being sure to push it on as far as it will go. Now remove the old plug.

06
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How Does the Spark Plug Look?

Ugly plug, pretty plug.
Old fouled spark plug (left), and new plug. Matt Wright

Take a look at the old plug. It should be a little dirty on the end, a little black with a little soot, the key phrase being "a little." If it's white or oily, this could indicate other problems so make a note of how they're looking. Also, check to see if the porcelain insulator is cracked.

Finally, take a look at how the end you pulled the plug wire off is set up. Some will just be threaded like a screw, and others will have a large metal cap on the end. Be sure your new plugs are set up like the old ones were.

07
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In With the New Plug

In with the new.
Carefully install the new spark plug. Matt Wright

With the wire end of your plug set up like the old one, you're ready to put it in the car.

But don't I have to set the gap with one of those fun tools?

These days you order plugs specifically for your car, and they come already gapped. I know some die-hards out there will strongly disagree (here come the e-mails) but I have never opened a new spark plug and had to reset the gap, never!

Put the plug (wire end of the plug in the socket) and holding just the extension, push it all the way in. Now carefully guide the spark plug into the hole. Try not to bang it on anything because this can screw up the gap or damage the plug. Begin to screw in the new plug by hand. Starting them off by hand instead of using the wrench will keep you from accidentally cross-threading one of the plugs. Screw it in by hand until it stops, then put the wrench on the end and tighten it snugly. If you have a torque wrench, you can torque it to spec, but if you don't, just make it tight without overdoing it. The metal in there is soft and can be damaged by over tightening.

Put the plug wire back on.

Now is the time to inspect for worn or broken spark plug wires, and if they're bad, replace your plug wires.

08
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Finishing Up and Testing it Out

New spark plugs and running great!
Install new spark plugs and you're ready to go!. Matt Wright

Repeat all the steps one plug at a time until you've done them all. Now start it up and listen to the purr!

*If you decided not to listen and pulled all the wires off at once, you might have mixed up the plug wires. You'll know if you did because it either won't start, will run really rough, or if you're very unlucky you'll hear a deafening backfire. Now you have to go and look up your engine's firing order, correspond that to the points on the distributor cap after you set the engine to Top Dead Center and put them all back on. Doesn't it sound easier to replace them one at a time?

While you are in there staring at everything, it might be a good time to inspect your plug wires. Safety first. Installing new plug wires is another simple job, and can be done at the same time even. You're done!

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Your Citation
Wright, Matthew. "Replace Your Spark Plugs." ThoughtCo, Mar. 20, 2017, thoughtco.com/replace-your-spark-plugs-281751. Wright, Matthew. (2017, March 20). Replace Your Spark Plugs. Retrieved from https://www.thoughtco.com/replace-your-spark-plugs-281751 Wright, Matthew. "Replace Your Spark Plugs." ThoughtCo. https://www.thoughtco.com/replace-your-spark-plugs-281751 (accessed September 25, 2017).