How to Replace Spark Plugs

Introduction

Using the right tools, almost anyone can deal with this maintenance item. Spark plugs should be changed every 30,000 miles, usually when your car is getting a major tune-up. If your car has faulty spark plugs you will experience trouble starting the car.

By: eHow Cars Editor

Length: 3:27

Comments: 25

View more articles by this author

Flag | RSS

(96)

Add to Favorites

URL:
Embed:

Instructions

Text Size: – +

Print Article

Difficulty: Moderate

Tips & Warnings:

Your socket set should have a "spark plug socket" (usually with a little padding/grip inside it) just for spark plugs.
Make sure the car is off and let the engine cool before changing the spark plugs.
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 badly or not at all. If you must take all the wires off at once, label them with white correction fluid or with masking tape and a marker.

Removing the Old Spark Plugs

Step1

Pull the hood release lever located under the dashboard.

Step2

Walk around to the front of the car, reach under the hood, find the latch and squeeze it. Open the hood.

Step3

Find the spark plugs, located in a row along one side of the engine (on an in-line 4-cylinder engine) and attached to thick wires, called spark plug wires. Cars with V-shaped engines (which can have 4, 6 or 8 cylinders) will have spark plugs and spark plug wires on both sides of the engine.

Step4

Change 1 spark plug at a time, always putting the plug wire back on before changing the next spark plug (see warning below).

Step5

Pull off one spark plug wire where it attaches to the plug. There is a little rubber boot at the plug end of the wire; pull on this part. Pulling higher up on the wire can damage the spark plug wire and cause it to separate.

Step6

Blow or wipe away any dirt or debris around the spark plug. You do not want anything to fall into the cylinder while the spark plug is out.

Step7

With the spark plug socket and a 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. Ratchets with flexible heads are especially helpful for hard-to-reach spark plugs.

Step8

Check the spark plug to make sure it needs replacing. A good spark plug should be lightly coated with greyish brown deposits. If heavy deposits are present, if the spark plug is black or if the electrode or core nose are damaged, the plug needs to be replaced.

Gapping the New Spark Plugs

Step1

Find the chart listing the proper "gap" for your plugs in your car's repair manual. The spark plug gap 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.

Step2

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

Step3

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 (the metal part at the very top) against a hard service.

Step4

After adjusting, measure again. Repeat this procedure until the gap matches the specification listed in your car's manual.

Step5

Repeat with each plug.

Installing the New Spark Plugs

Step1

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

Step2

Tighten the plugs with a socket wrench until snug. Do not overtighten.

Step3

Replace the spark plug wires. Usually, you will hear a soft pop when the plug wire snaps onto the plug.

Step4

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.

Comments

dvinyard said

Flag This Comment

on 7/19/2008 They forgot the most important part>>>>>>>>>> USE A TORQUE WRENCH AND TORQUE THE PLUG DOWN TO THE CORRECT TORQUE SETTING. Undertorqueing and overtorqueing both have serious consequences (FROM NGK.COM):

"Torque is one of the most critical aspects of spark plug installation. Torque directly affects the spark plugs' ability to transfer heat out of the combustion chamber. A spark plug that is under-torqued will not be fully seated on the cylinder head, hence heat transfer will be slowed. This will tend to elevate combustion chamber temperatures to unsafe levels, and pre-ignition and detonation will usually follow. Serious engine damage is not far behind.

An over-torqued spark plug can suffer from severe stress to the Metal Shell which in turn can distort the spark plug's inner gas seals or even cause a hairline fracture to the spark plug's insulator...in either case, heat transfer can