2016~2023: CX-9 41K spark plug change, found NGK plugs in the wild

[sm1ke]

Just changed plugs in my 2018 cx9. 134,000km. Old plugs looked fine. Dealer wanted $400 to do the plugs and clean fuel rail. Next time I will automatically remove the hose that interferes with inserting coil. Did rear diff and transfer case, serpentine belt. Noticed while I was in that area that the water pump and belt tensioner will need to be done in the near future.

How did the fluid change go? Did you lift front and rear at the same time to keep the car level while draining and filling?

Also, just so I can learn from your experience, would you mind explaining why the water pump and belt tensioner will need to be replaced on your car soon? Was the pump leaking?

 

[roundle1979]

Just changed plugs in my 2018 cx9. 134,000km. Old plugs looked fine. Dealer wanted $400 to do the plugs and clean fuel rail. Next time I will automatically remove the hose that interferes with inserting coil. Did rear diff and transfer case, serpentine belt. Noticed while I was in that area that the water pump and belt tensioner will need to be done in the near future.

What leads you to believe that the water pump is getting close, weeping?

 

[DustyB]

For the fluid exchange I used ramps on the front and floor jack to raise rear. Positioned floor jack on differential to lift backend. I just eyeballed level. It was close enough as I got all the fluid to drain from diff and ptu. The height was great as well as I was able to use the creeper easily. I only changed the serpentine belt as after I removed the under panels I noticed that the water pumped may have a small leak as I saw green fluid on the pump. Also the tensioner was sweating a small amount of hyd fluid. I didn't have the pump or tensioner so I left the water pump belt on - which looked in great shape anyway - as I needed the car the next morning. Once I get those parts I'll complete those jobs.

What leads you to believe that the water pump is getting close, weeping?

Yes

So for the last bolt, you're unable to tighten the bolt any further, and the coil pack feels a bit more loose than the others? It's possible that you crossthreaded the bolt that snugs the coil pack. You could probably remove the bolt and try using a thread chaser to repair the threads, but then you'd risk getting metal particles in places you don't want them.

This is just a temporary solution, but I would find a plastic washer that would fit between the bolt and the coil pack, something just thick enough to shim the bolt up against the coil pack. Cut them on one side so that you can slide one or more under the bolt without having to remove the bolt.

Remove at least one end of the closest hose that prevents easy access for installing the coil. I struggled for a bit with hose attached trying to seat the coil over plug. As soon as I removed the upper end - on plate above coils - I was able to align coil directly over plug and it slid on effortlessly. If the head of the coil where the bolt insets isn't on the bottom portion the plug isn't seated.

 

[roundle1979]

Finally got around to changing my 2018 CX9's plugs at 61K miles. I used the NGK DILKAR7M8 NKG Laser Iridium (from Amazon, $20 each). Installation is kind of a pain but it's do-able in about 20-30 minutes.

It was also really easy to remove the coils from the plugs (not my experience with some other makes). Old plugs came out in decent shape (gap and electrode suggest the plugs could have gone much longer). The color differences in photo are mostly attributable to lighting.

So far, no noticeable changes in idle or performance. Will report back on MPGs after a few tanks of fuel.

Alright, have done a few tanks, and still getting the same (crappy) 19-20 MPG combined.

Suspect that these factory plugs are fine for 80-100K.

 

[PTguy]

I put in new plugs at 40k and noticed slightly peppier performance. I track the mpg imprecisely on the display, usually 24-26. Your 19-20 mpg is either a bad calculation or something wrong with that car.

 

[youri]

I only changed the serpentine belt as after I removed the under panels I noticed that the water pumped may have a small leak as I saw green fluid on the pump.

Small leak is normal, large leak no.

See this tsb from mazda with regards to water pump being replaced prematurely.

https://static.nhtsa.gov/odi/tsbs/2024/MC-11000775-0001.pdf

 

[DustyB]

Small leak is normal, large leak no.

See this tsb from mazda with regards to water pump being replaced prematurely.

https://static.nhtsa.gov/odi/tsbs/2024/MC-11000775-0001.pdf

Thanks for the heads up and information. As per the TSB I would think this is normal and would not require a replacement. I will put the car back up on ramps and take a closer look at that area to confirm condition. Thanks again.

 

[roundle1979]

I put in new plugs at 40k and noticed slightly peppier performance. I track the mpg imprecisely on the display, usually 24-26. Your 19-20 mpg is either a bad calculation or something wrong with that car.

I never reset 'trip b' and reset 'trip a' at every fill up. It's pretty consistent.

We mostly do short, urban drives. I also have roof racks (Thule Aero Blades) installed year round.

 

[Candurin]

These are the only spark plug socket I will ever use:
View attachment 311783
View attachment 311784

No more rubber insert that can shrink, crack, fall out.
No magnets that can shatter.
No need for extensions that can get cockeyed or detach from the socket.

Only (patented) metal clips that grips the spark plug on the hex fastener head that will last forever, and work reliably even on a burning hot engine without fear of damaging the socket.
View attachment 311785

Professional grade, and not cheap, and easily costs as much as one spark plug or two. But if you don't want any headaches, buy it. If you're a mechanic, buy it.

I don't like to **** around with cheap tools any more unless I only can see them being used once. Good tools just makes working on cars much less frustrating and can keep you in good mood.

I realize you posted this awhile ago, but thank you for this. Picked up both sockets for around $70. I have zero issues buying quality, recommended tools!

The cost was easily justified as I’m going my wife’s CX-9 and my CX-5 at the same time.

These will definitely get use!

 

[sm1ke]

I realize you posted this awhile ago, but thank you for this. Picked up both sockets for around $70. I have zero issues buying quality, recommended tools!

The cost was easily justified as I’m going my wife’s CX-9 and my CX-5 at the same time.

These will definitely get use!

Since you ordered these recently, could you provide the part number for the longer socket? I just did the plugs on my CX-9 and it was annoying as heck when I'd finish tightening the new plugs in, and the extension would release from the socket before the socket came off the plug.

 

[Candurin]

Since you ordered these recently, could you provide the part number for the longer socket? I just did the plugs on my CX-9 and it was annoying as heck when I'd finish tightening the new plugs in, and the extension would release from the socket before the socket came off the plug.

Sure! Here's both part numbers as it was a bit difficult to decipher from the photos:

Ko-ken 3300C.180-14 is the 180mm (~7") socket

Ko-ken 3300C.250-14 is the 250mm (~9-3/4") socket

 

[bdlaey1976]

2018 CX-9 170k 2.5
So I got the code that said ignition coil pack cylinder two, figured I would replace that and all four spark plugs.
170k miles
Now I feel I have a knock I never had before.
Based on the spark plug, it also leads me to believe that the coil pack was probably fine.

Drive it with a knock
Or do I need to do something else next?

 

[roundle1979]

Drive it with a knock
Or do I need to do something else next?

That plug looks awful.

Is a piece of the electrode missing or is it just bent? That looks like mechanical damage vs detonation damage.

How is your compression? Any chance you have a borescope?

 

[bdlaey1976]

That plug looks awful.

Is a piece of the electrode missing or is it just bent? That looks like mechanical damage vs detonation damage.

How is your compression? Any chance you have a borescope?

My friend is going to bring over a bore scope and a compression tester this week.
But before I changed the ignition coil and the plugs, it had a horrible hesitation. Getting up to speed drove awful feeling like it wanted to stall.
I’ve done 100+ miles since the plugs and ignition coil. It drives so much better than before but I might still have some damage in there I guess.
My friend who said he could bring over the equipment, thought what I was hearing was coming from the valve cover.

 

[roundle1979]

Is the plug electrode bent or broken? If broken, definitely get the bore scope in there.

Driving 100 miles like that was probably not ideal. Hopefully the car was smart enough to cut fuel to the cylinder with the failed coil / plug.

I had a VERY old BMW many moons ago with VERY high compression pistons that would cause knock and pre ignition. I would occasionally destroy spark plugs and they would come out looking a bit like yours (w/ 'repositioned' electrodes).

Also, in my experience, if one ignition coil goes bad it is just a matter of time before others follow. If there's no engine damage, I'd probably replace the other three.