In this guide, you will find step-by-step instructions on how to change the spark plugs on a Mazda with a four-cylinder engine. These instructions apply to the inline 4 engine found on Mazda 2, 3, 5, 6, 323, Protege, etc.

Replacing spark plugs on a Mazda engine requires a few basic tools and two hours of labor.

Symptoms

• Check Engine Light On
• Poor Engine Performance
• Decrease in MPG
• Engine idles roughly
• Mazda engine misfires
• Hesitation during acceleration
• Fault Codes for cylinder misfire such as P0300, P0301, P0302, P0303, P0304.

What you will need

Replacing the spark plugs on a Mazda requires a few basic tools and parts.

Tools Required

• Spark Plug Socket
• 4-inch extension
• 3/8 Ratched
• 10mm socket

Parts Required

• Mazda Spark Plugs
  The two options we would recommend are:
  1. NGK Iridium Spark Plugs. If you are looking for the best aftermarket spark plugs for Mazda a good choice are NGK Spark Plugs for Mazda. They come pre-gapped for Mazda and also have great reviews from Mazda owners.
  2. OEM Mazda Spark Plugs
     OEM Mazda sparks plug at the dealer cost over $20 per spark plug. If you prefer OEM spark plugs buy them online to save money.

Procedure

The following instructions show you how to change spark plugs on a Mazda four-cylinder engine.

This is one of the most common Mazda engines found on Mazda 3, Mazda 5, Mazda 6, CX-5, CX-7.

1. Park vehicle. Park you Mazda on level ground. Allow the engine to cool down.

2. Pull the hood release and open the hood.
3. Disconnect the negative battery terminal. The negative terminal is difficult to reach due to the small space between the battery and the firewall.  
4. Remove the engine cover. Check for bolts on top of the engine cover. If no bolts are present, grab the engine cover with both hands and lift it up. In this Mazda, there are no screws to secure the cover. Only tabs underneath the engine cover. 
5. Unplug the electrical connector from the ignition coil. Press on the small tab then pull. Do this for all four coils.
6. Remove the 10mm bolts that secure the coil in place. Pull the coils out.

7. Remove Spark Plugs.  Use the spark plug socket, extension, and ratchet to remove the spark plugs from your Mazda. 
8. Use a magnetic pickup tool to pull out the spark plugs.

9. Install new spark plugs. Install new spark plugs on your Mazda.  
10. Tighten the spark plug finger-tight until it reaches the cylinder head.
11. Torque the spark plugs to 20 ft.lb. Verify torque value for your engine. 

12. Reinstall Ignition Coils. 
13. Reinstall coils and connect the electrical connectors.

14. Reinstall Engine Cover 
15. Replace the engine cover.
16. Start the vehicle and ensure it is running properly. 

Mazda Spark Plug Replacement Interval

The recommended interval spark plug replacement for most Mazda vehicles with a 4-cylinder engine is every 75,000 miles. This value can vary depending on the spark plug type installed in the engine. Check the owner's manual to verify. 

Copper spark plugs on older Mazda vehicles need to be replaced every 30,000 miles.

Torque Specifications

Tighten the spark plug to:

• 15 lb. ft. - 14mm spark plugs.
• 20 lb. ft. - 18mm spark plugs.

Spark Plug Gap

Mazda factory spark plug gap is typically in the .045 to .057 range.

Iridium spark plugs such as Denso Iridiums for Mazda come pre-gapped at 0.044 and should not be changed.

NGK Spark Plugs for Mazda come pre-gapped at 0.054. Do not gap iridium spark plugs.