How To Change Spark Plugs On a Mazda 3.0L V6

In the old days, changing spark plugs on your car, wasn't that big a deal, well not any more. You would think on how to change spark plugs on a Mazda 3.0L V6, wouldn't need a "How To" guide. But here you are, looking into how to accomplish this no so easy task. This article covers the Mazda 3.0L V6 from 2004 to 2008.


Spark Plugs On a Mazda 3.0L

The first thing you need to understand. This is one of those jobs where you are doing more than just changing the spark plugs. This job requires some disassembly of the engine. Which means, while you are there, there is other things you should replace while you are at it. Let’s dive into this really fun job and look at what all needs to be done.

What Else to Changing Spark Plugs on a Mazda 3.0L

Here is a quick layout what you will be getting into on changing spark plugs on a Mazda 3.0L. This layout will help you decide now if you even want to attempt it.

Some models of Mazda’s with the 3.0L may be more or less difficult. This article is based on the Mazda 6 and the MPV. Overall, they will all be about the same.

In order to get to the spark plugs on a Mazda 3.0L, you have to remove the upper plenum.

Spark Plugs On a Mazda 3.0L

The plenum has to be removed for the rear three spark plugs only. However, this is going to be your hardest task out of the whole project.

In order to remove any of the spark plugs. You first have to remove the coil packs that are mounted on top of the plugs.

Spark Plugs On a Mazda 3.0L

There is one more part that should be changed while you have everything apart. The PCV Valve, it is buried below the plenum. If there was ever a time to change the PCV Valve, this is it.

So, you can see, this isn’t an impossible task, but more than just a simple changing of the spark plugs on a Mazda 3.0L V6. All in all, you can do this job, completely unexperienced, in and around 3 hours.

How Often Do Spark Plugs on a Mazda 3.0L Need to be Changed

Many spark plugs today can go 100000 miles before needing to be replaced. However, on the Mazda 3.0L between 04 and 08. The answer would be to replace them every 75000 or every 60 months.

Coil packs can technically go 100000 miles, but there is a catch. When a spark plug starts declining in performance, it causes the ignition system to decline.

Just like in the old days when cars had distributors. When a spark plug starts building up resistance not being able to fire as good as it once did. The ignition backs up into the distributor cap, causing the cap and rotor to burn out sooner.

This applies to coil packs as well. When the spark plug starts to not fire as efficiently, it causes the coil packs to overheat and burn out.

So, as mentioned above, since you have so much to do to change the spark plugs anyhow. Keeping the plugs and the coil packs changed at the same time is the most logical way to go.

Now that you know that how declining spark plugs on a Mazda 3.0L can wear down the coil packs. I hope you understand why it is important to change both at the same time.

Always Replace in Pairs and Sets

There are some shops that shouldn’t even be in business, that will change just the failing plug or coil pack. Do not follow their practice of this stupid mindset.

Always change tune-up parts in pairs or sets. Meaning, no matter how many cylinders your engine has. Replace all spark plugs as a set. This includes coil packs or spark plug wires as well.

Understand, if one plug is starting to fail, that just means the others are right behind it. Imagine the expense on an engine like this Mazda 3.0L. Where you have to spend 3 hours to remove the plenum each time to replace the rear spark plugs.

It makes no sense to replace any parts like for tune-ups or brakes or even headlamp bulbs, one at a time.

You can learn more about this by reading my article on “Buying in Pairs to do the Job Right.”

Procedure to Changing Spark Plugs on a Mazda 3.0L

For ease for you to follow the steps, I have added a table of content. Not knowing your level of mechanical expertise, this can get you to the section you need most quickly.

Quick Steps

  1. 1
    Remove the plastic engine cover by loosening the (3) 10mm nuts. You will want to use a deep well socket.
  2. 2
    Pull the (3) hoses off from the back of the plenum. Two will take pliers to to squeeze the clamps on the hoses.
  3. 3
    Disconnect all the electrical connectors to the throttle body. Refer to the Video (2:14).
    You do not have to disconnect the electrical connector or the hose to the EGR Valve.
  4. 4
    Remove the (3) 8mm bolts to the EGR System Brackets to allow it to set aside, you do not have to remove it.
  5. 5
    Remove the (2) hoses from the Air Breather Tube and one from the Valve Body where the Tube connects to the Valve Body. Loosen the 10mm clamp bolt to the Air Breather Tube where it connects to the Valve Body and pull it back. Unfasten the Air Filter box top and remove the entire Air Breather Tube with the Breather Box Top. 
  6. 6
    Disconnect the wiring harness retainer clips along the front site of the plenum. Refer to Video (5:38)
  7. 7
    Remove the (8) 10mm Plenum bolts and set the plenum off to the front side. No need to remove, it is flexible enough to move around to allow you to get to the coil packs and spark plugs.
  8. 8
    Remove the electrical connectors to the coil packs. Remove the 8mm bolt on each coil pack, then twist and pull upward to remove. Note: This would be a good time to replace the PCV Valve. See Video
  9. 9
    Using an air hose or canned air, blow the holes where the spark plugs are out to remove any dirt or debris that can fall down into the cylinder once the spark plug is removed. Remove the spark plugs.
  10. 10
    Installing the new spark plugs. Gap your plugs first, they should be around .044in but some under hood stickers and manuals call for .052in. May want to check with you manual first. After gapping, coat the threads of the plugs with anti-seize compound before installing.
  11. 11
    Push new coil packs onto the spark plugs. Place a dab of di-electric grease in the hole of the coil pack and spray silicone lubricant on the out boot of the coil pack first.
  12. 12
    Replace the (6) o-rings on the plenum with new ones. Wipe the surface that the plenum bolts to down with a solvent to remove dirt and oils.
  13. 13
    Bolt plenum back down, refer to torque specs and bolt pattern below.
  14. 14
    Reassemble everything in the reverse order.

How To Video

Plenum Torque Specs

6ft-lbs to 9ft-lbs

72in-lbs to 108in-lbs

Recommend using an Inch Pound torque Wrench at 95in-lbs to 100in-lbs

Plenum Torque Bolt Sequence

how to remove mazda 6 intake plenum

Firing Order And Cylinder Location

mazda 3.0l cylinder location

Tools And Materials

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  • Derek Davis says:

    I wanted to take a moment to commend you on the outstanding quality of your blog. Your dedication to excellence is evident in every aspect of your writing. Truly impressive!

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