40,000 Mile Spark Plug replacement on 2016 CX-9

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Winnipeg Canada
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2017 CX-9 GT
Nice, how was the job? Fairly easy/straightforward? My CX-9 just hit 53k so I've got little more time before I change mine out.

Where did you order the plugs?
I got the plugs from Napa Auto parts right here in town. They actually had them in stock (RockAuto lists them as Currently unavailable). The dealership wanted $50 a piece but Napa sells them for $30. Not sure the Mazda logo on the spark plug is worth the extra $20 so I went with Napa. :)


It was mostly straight forward. If you see how it's done on the CX-5, it's a total breeze. The CX-9 however has stuff in the way that you need to move. I wasn't sure exactly which bolts were needed to be removed, but there's about 5 on a metal plate that sits right over spark plugs #2, #3 & #4. Also, some hoses keep you from moving it enough, so I had to remove another 2 bolts. I should take a photo and post here exactly which ones were needed to be moved. Aside from that, it's straight forward.

So I didn't use any thread anti-seize as NGK recommends against it. I did use dielectric grease on the boot of the plug. Oh, I also disconnected each spark plug wire from each ignition coil, just to make it easier to pull out the coils, although probably not necessary. I took the liberty to also put some dielectric grease around the spark plug wire connector housing, but not on the electrical conductors themselves. This will help keep moisture out and make it easier to disconnect if needed in the future. Ya, I like to take my time with these little jobs and do these little extra things that probably don't matter much.

Btw, I did notice a bit of oil on one of the plugs I pulled out. Not a lot, and it's mostly just on the end of the plug although the electrodes themselves looked clean. I believe that was plug #4. I might want to pull that plug again in about 6 months and inspect it, see if that's a real issue or not. Oil on the plugs could indicate a bad piston ring or valve guide. But it's so little that I'm not overly concerned right now. Mazda did inform me that the prior owner did the oil changes on time, so that's a bit reassuring.
 
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Winnipeg Canada
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2017 CX-9 GT
Here's is a photo of the plug I was talking about:

PXL_20210303_195902895.jpg


As you can see, the one on the left has slightly more oil and it looks more wet compared to the other one.
 
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Ottawa, Ontario
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17 Mazda 6 GT
From that video that guy puts a ton of anti-seize on the threads. Put as little as possible. NGK recommends to NOT use anti-seize on the threads because the threads are specially plated to prevent seizing. However, if you DO use anti-seize, be sure to reduce the torque applied (they recommend by 20%) because the anti-seize reduces the amount of thread friction but not the thread tension. Torque wrenches aren't affected by tension, so you could damage your head if you're not careful.


Also, I didn't notice him using any dielectric grease on the plug boot. The purpose of that is to seal it in and prevent moisture. Be sure to use that, it's cheap and a really good idea.
Be a little leery of what people post on YouTube. According to the posters, it's gospel of course, but reality is somewhat other than that.
Most of these posters are not trained or professionals. They are just shade tree weekend warriors hoping to make a buck or two on YouTube.
For example, just look at the videos of guys doing rear brake jobs on newer Mazdas with EPB.
Most of them don't put it into maintenance mode or even seem aware that it's part of the process.
Lots of disinformation and improper procedures out there. Be careful.
 

helbigtw

T-Rav
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PA
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08 CX-9 GT FWD
Glad to see good information on new units. I cross threaded the last plug on my v6 because I didn't wait overnight to let the motor get completely cool. Had to buy a whole pile of new Motorcraft plugs to basically re-thread the hole. 24k miles no ejection thankfully. Weekend warriors learn from their mistakes.
 
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2016 Mazda CX-9 GT
Well this weekend I decided to replace the spark plugs on my own this time. The first time the dealer did them at 40K. I am at 86K now. All went smooth until I was bolting down the bolt that held the third ignition coil down. I had it almost secure and the bolt started tightening but still not securing the coil enough. I thought there may have been grit in there and went one more turn and the bolt snapped. It must have not been going in right. This was a stupid mistake on my part.
Thank goodness the coil packs sit pretty tight. I am no mechanic and I did not want to try to remove the broken bolt on my own. For now, I just used a little bit of gasket sealant around the edge and where the bolt broke to hold it in place. So far that has worked.
I assume the entire valve cover would have to be replaced which I didn't want to tackle nor pay for it yet.

The other thing I notice now is definitely more power. No delay in acceleration but I did notice more of a "whoosh" sound when accelerating and in certain gears I hear what sounds like a blow off valve. Is there anything on the rail that one unbolts and move out of the way when accessing the spark plugs that may have come loose? I don't have any codes and the car is running fine. Not sure if it's just something I have not noticed before.
 

sm1ke

Work In Progress..
Moderator
Contributor
:
Canada
:
'18 CX-9 Signature
Well this weekend I decided to replace the spark plugs on my own this time. The first time the dealer did them at 40K. I am at 86K now. All went smooth until I was bolting down the bolt that held the third ignition coil down. I had it almost secure and the bolt started tightening but still not securing the coil enough. I thought there may have been grit in there and went one more turn and the bolt snapped. It must have not been going in right. This was a stupid mistake on my part.
Thank goodness the coil packs sit pretty tight. I am no mechanic and I did not want to try to remove the broken bolt on my own. For now, I just used a little bit of gasket sealant around the edge and where the bolt broke to hold it in place. So far that has worked.
I assume the entire valve cover would have to be replaced which I didn't want to tackle nor pay for it yet.

The other thing I notice now is definitely more power. No delay in acceleration but I did notice more of a "whoosh" sound when accelerating and in certain gears I hear what sounds like a blow off valve. Is there anything on the rail that one unbolts and move out of the way when accessing the spark plugs that may have come loose? I don't have any codes and the car is running fine. Not sure if it's just something I have not noticed before.

I would definitely try to keep an eye on that bolt to make sure it doesn't back out. It might be a good idea to have shop look at the broken bolt to see if they can extract it. Maybe you won't need a new valve cover?

Did you disconnect the battery while changing the plugs? The difference in the way the car runs could possibly be due to the ECU relearning your drive patterns (if you did disconnect the battery).
 
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2010 CX-9 GT
There are multiple ways to remove a sheared off bolt. If you aren't comfortable trying one a mechanic could probably get it out without having to resort to replacing the valve cover.
 
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2016 Mazda CX-9 GT
I would definitely try to keep an eye on that bolt to make sure it doesn't back out. It might be a good idea to have shop look at the broken bolt to see if they can extract it. Maybe you won't need a new valve cover?

Did you disconnect the battery while changing the plugs? The difference in the way the car runs could possibly be due to the ECU relearning your drive patterns (if you did disconnect the battery).
No, I did not disconnect the car battery. The car is running fine other than hearing the intake of air more and what sounds like a BOV sound. It has died down a bit now that we have been driving it for a few days.
 
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2016 Mazda CX-9 GT
There are multiple ways to remove a sheared off bolt. If you aren't comfortable trying one a mechanic could probably get it out without having to resort to replacing the valve cover.
That's my next step. I don't want to take it to the dealer as we know they will go the expensive route.
 
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Winnipeg Canada
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2017 CX-9 GT
Older cars didn't even have that bolt. *shrug* If the plug isn't firing right you'll get a misfire code. If so, you really should fix it. But otherwise, probably not a big deal.