How To Identify Failing Spark Plugs in Your Mazda

Mazda spark plugs come with a factory recommended change interval of 100K-120K miles. However, sometimes spark plugs might go bad earlier due to, oil contamination, carbon buildup, or something else.

When a spark plug fails, some or all of the following issues will arise:

  • Poor drivability
  • Trouble starting the engine
  • Increased fuel consumption
  • Sluggish acceleration

A bad spark plug or two won't blow up your engine or anything drastic, but it will really affect the way your engine performs. If you want to keep your engine in tip top shape, replace your spark plugs as soon as they go foul.

Finding Your Spark Plugs

The best way to identify a bad spark plug is to visually inspect it. See below for an overview of how you can access your spark plugs. The steps may vary a bit, depending on the Mazda model you have.

  1. Pop the hood and then prop it up.
  2. There's a black cover in the middle of the engine. Remove it. It may be bolted down with screws. Otherwise, it'll just pop right off.
  3. Underneath are electrical connectors that connect to the spark plug ignition coils. Disconnect all of them.
  4. Remove all of the ignition coils. To do this, remove the bolts holding the coils down. A good rule of thumb is to take out one ignition coil at a time so you don't mess up the firing order or accidentally drop a bolt into another chamber.
  5. Now you can see the spark plugs in the combustion chambers. Grab a spark plug socket and then remove one of the spark plugs.
  6. Examine the spark plug and then put it back into the combustion chamber.
  7. Repeat steps #5 and #6 with the rest of the spark plugs.

What Does a Fouled Spark Plug Look Like?

When you have a spark plug in your hand, you need to look for signs that the spark plug is no longer functional. Here's what you have to look for:

  • Dull black carbon deposits on the insulator, electrodes, and shell
  • Oily deposits on the insulator, electrodes, and shell
  • Yellowish or brownish cinder-like insulator deposits on the insulator, electrodes, and shell
  • Melted electrode
  • Electrode erosion
  • Any cracks or corrosion
Plug closeup

Notice the oily deposits on the spark plug? That means the spark plug needs to be replaced. Photo credit: Robert Couse-Baker under the Attribution 2.0 Generic (CC BY 2.0) license

Replacing Your Spark Plugs

You don't have to bring your Mazda to a shop to have your spark plugs replaced. If you're able to check your spark plugs without any issues, you can certainly replace them yourself. The process is basically the same, except you would be putting in new spark plugs instead of your old ones.

If you're looking for replacement spark plugs, we have some pretty great prices for genuine OEM spark plugs. Check them out here!