Tune-up/Replacing Engine Spark Plugs

The key maintenance parts that require service for a tune-up are the air and fuel filters, spark plugs and oil change. In this section I will show you how to replace spark plugs.

Tools for the job

You will need the following tools to perform this repair;

• 3/8″ ratchet
• 5/8″ sparkplug socket
• 3/8″ extension 12″ long
• 10mm socket

Here is a 2004 Chevrolet Malibu with a 2.2 liter EcoTec 4 cylinder engine

This engine puts the spark plugs in from the top. The EcoTec cover on the top is a coil cover that has to be removed

Locate the electrical connector for the coil at the right end of the cover

Unplug and slide the connector off

Next locate the hold down bolts for the coil cover

There are 4 bolts to remove (10mm bolts)

Ignition Coil

The ignition coil is the part that supplies a large amount of voltage to the spark plug in order to ignite the air and fuel mixture inside each cylinder.

Make sure to lift the coil assembly strait up to avoid damaging the 4 long spark plug resistors that attach the coils to the plugs.

With the coils removed you can see the access holes for the spark plugs

Spark Plug Sockets

The two main spark plug socket sizes are 5/8” and 13/16”. There are rubber inserts inside of the plug socket to prevent damage to the porcelain spark plugs when installing them. Most tool kits purchased today come with these two sockets.
There are other special application spark plug sockets, but these two are the most common in the industry.

This particular socket is a 5/8” wobble socket and I’m using a 1 ft. locking extension to help and keep the socket from sticking in the plug hole after installing the new plugs.

Loosen and remove the old spark plugs

Locating Tune-up Parts

If you need to purchase spark plugs, avoid going all over town to find them. Refer to the parts link and use one of the auto parts stores to locate spark plug types, cost, and store locations to save you time and find the best deals.

Here is a comparison of the old and new spark plugs.

The wear parts of the spark plug are the tip and the electrode. Over time, the spark jumping the gap wears away at the metal. This increases the distance that the spark has to jump. If the distance increases the spark gets hotter which can create wear on the aluminum pistons within the engines.

Here is one type of spark plug gapping tool. This one starts at .020” and goes to .100”

All spark plugs have recommended gap specifications that need to be set. When purchasing your sparkplugs ask your parts person to look up the gap specification.

Slide the tapered tool into the gap and turn until the desired specification is met.

Install and tighten the new spark plugs.

Re-install the ignition coil assembly and electrical connector.

Start up and check the idle and running quality of the engine to finalize the repair.

More Tune-up Articles

For more tune-up articles, refer to the following sections to see how to complete your tune up.

How to change an air filter
How to clean a throttle body
How to change your oil and filter
Maintain your fuel system

Comparison Pricing

Do it your self
$4 to $15 per plug depending on the type, vehicle, and number of cylinders.
This 4 cylinder was $6 each x 4 = $24 plus tax

Repair shop costs
$15 to $25 per plug with mark up and approx one hour shop labor @ $80
This 4 cylinder could cost you $128