Changing Spark Plugs (L15A VTEC)

I did the switch on my 2007 Honda Fit Sport, and I know this DIY will work for most any GD3 with the L15A VTEC engine. I do not know at this time if it will be exactly the same on the GE8 L15A i-VTEC engine. It should be pretty close. The i-DSI L series engines found in JDM vehicles will have a different course of action since they have 8 plugs to worry about.

So first off, here are the tools you will need:

  • 10mm socket
  • 5/8″ Spark Plug Socket
  • Regular Ratchet and a Torque Wrench
  • Dielectric Grease
  • Anti-Seize or other lubrication
  • Ice cold beverage of your choice

Here we have tools and parts needed. I forgot to get some anti-seize for the plugs, so I used some Castrol synthetic oil I had in the garage.
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I went with some E3 DiamondFire plugs. I have heard so many good things about these new plugs. Every test I have seen, they make real power on both an engine and chasis dyno. sometimes as much as 12-14hp! They are also able to be used in forced induction and nitrous applications, which of course you can’t do with platinum plugs. I got mine from Summit Racing High Performance Car and Truck Parts l 800-230-3030 for less than $5 each.
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I figured out afterward, that I didn’t really need to remove the cam cover, but I had already done it. You can skip that step since it would appear that it really doesn’t get in the way much.
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Looking on the rear of the engine above the exhaust manifold heat shield, you will see the 4 coil packs with blue wiring harness clips attached.
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You will now use the 10mm socket and ratchet to remove the 10mm bolt holding the coil pack onto the head.
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And now you want to unplug the blue wire harness from the coil pack. You can then pull the entire coil pack out of the spark plug well.
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Now you will use the 5/8″ spark plug socket with a medium extension in order to reach all the way down into the spark plug well to the spark plug. By using an actual spark plug socket instead of a regular socket, the rubber o-ring inside will grip the plug and allow you to pull it out of the head after loosening.
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There are many references you can check in order to properly read a plug and it’s performance. This plug is functioning great. And the engine is neither running too lean, nor too rich. The light tan coating around this plug, with no oily residue means this engine is running very good. Considering I only have 19,000 miles, and I run Royal Purple Race Oil, and other than my SSR Intake and muffler delete, I have no other performance mods, this is too be expected.
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I was a bit surprised to see that the OEM Honda plugs were Denso Iridium. Nice, expensive, high quality plug! No wonder they last 100,000 miles before replacing.
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And here we compare the Iridium plug with the E3 DiamondFire plug.
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The E3 plugs come pre-gapped. If you have to gap your plugs, then .044″ is the recommended gap size. It is at this point you will want to coat the threads with either anti-seize or a quality oil to ensure that you get proper torque when installing the plugs. Also make triple sure the washer is on the plug. Iron heads have a tapered seat plug, and aluminum heads use a washer type plug.
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When installing the new plugs, you want to start with just the extension without the ratchet. You will want to be careful to not cross-thread the plug into the head. Remember this Honda head is aluminum and you can very easily tear up the threads of this rather soft metal. So be careful and take your time. Tighten the plug down finger tight. You will want to then finish it up with a torque wrench to around 15ft/lbs. I have tried to locate an exact spec, but I have not been able to yet. I do know that most Honda aluminum heads require a spark plug torque of between 13-20ft/lbs. Be careful to not strip out the threads by putting the nut-buster super-grip tightening wrench of death to it.
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Now you will need the dielectric grease to coat the interior of the coil pack. This will ensure good conductivity between the coil and the plug. It will also keep moisture out. Use a generous amount.
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Now re-install the coil pack onto the spark plug.
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You want to be sure and also either use anti-seize on the coil pack retaining bolts or a quality oil, as I did in my situation.
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You will need to again be careful to not cross-thread the bolts into the aluminum head. Again torque them down to around 10-15ft/lbs.
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Remember to re-attach the blue wire harness clip to the coil pack.
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You will want to repeat these steps for the other three plugs.
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Triple check to make sure everything is torqued down correctly and that all coil pack connectors are connected. Then reinstall the cam cover if you removed it like a dummy like me!

Finish off your ice cold beverage and enjoy your new plugs!!

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