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Discussion Starter · #1 ·
Hi everyone, I have two questions regarding the 2021 Mazda 3

Cylinder Deactivation - how can I verify that the car I am looking at does not have this? it is a 2021 AWD select Hatchback and I've seen online that it doesn't have it but is there any way to verify this while in the car?

Direct Injection - I've seen that Mazda has mitigated DI issues by keeping it at a hotter temperature... but I am still concerned about carbon buildup. it seems that the only car with dual injection is a Toyota Camry... should I be concerned about this? How would I even tell that it needs to be cleaned before it's too late and causes engine issues? am not good with cars and don't know how to look inside.

I was hoping for an extremely reliable car and this looks so much better than any Toyota of similar class but want to make sure that this isn't a concern. All these posts about Walnut Blasting have me scared. I've seen posts about Mazda's going over 200k miles as well.
 

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Hi everyone, I have two questions regarding the 2021 Mazda 3

Cylinder Deactivation - how can I verify that the car I am looking at does not have this?

Direct Injection - I've seen that Mazda has mitigated DI issues by keeping it at a hotter temperature... but I am still concerned about carbon buildup.
Here are my answers, to the best of my ability:

CD - In the infotainment, go into the menu "Information," then "Fuel Efficiency Monitor." When you see the graph of your fuel economy, turn the knob and a few sub-menus will show up. If there is a sub-menu like "engine status" (I don't remember exactly what it's called) that will display either 4 or 2 cylinders, the vehicle has CD. If there is no such sub-menu, you're in the clear.

DI - From my research, as long as the valvetrain components don't endure sustained periods of time in the carbon-buildup temperature range, the lack of fuel flowing over the valves shouldn't be an issue. The 2.5L's track record seems to match up with that assumption, considering it's been in use for many years without known buildup issues. I've seen videos explaining carbon-buildup and seen Mazda's engineers explaining their engine design regarding it, and I don't think you should be concerned. There's no easy way of inspecting for carbon-buildup since there's no easy way to look at your valve stems; but you can suspect it as a contributing factor if your engine isn't running smoothly.

My 2019 had a lot of issues (nothing major), but my 2021 Turbo seems to have all of the issues ironed out, at least during my half-year of ownership. I certainly expect my car to last 200,000+ miles.
 

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Unfortunately, the only way to really tell is as daniellee003 mentioned above.
From what I have researched, in Canada none of the Mazda 3's have CD
In the US, the higher end models (Premium trim) MAY have it, and AWD models MAY have it.
The base, SE and Preferred FWD models do not have it.
 

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Not sure about CD, but for DI it really isn't a problem. Many manufacturers use DI and have done so for years. It's been a rocky road, but overall they have it figured out now. Both Honda and Toyota use DI as does Hyundai. Ford does as well and has been playing with it for years.

Most modern DI uses an extra injector in the intake to get a bit of fuel on the valves. Mazda (to my knowledge) is the only one that solves it by heating up the valves. It's not perfect, but it's close. Carbon buildup that actually causes any problem is virtually unheard of. Might be an issue if you're only taking short trips in city.

I got curious and pulled the intake off to inspect and clean at 120k kms. Yes there was carbon, but not a lot. Cleaning it out made no difference at all. I documented here in a thread if you're curious.


On the flip side, I helped a good friend do the same job on his 2012 Hyundai accent which is also DI. That thing was a hot mess. So much oil in the intake it was rediculous. It was like a pile of black mud in there. It ran like a new car when we were done, but you know we will have to do it again one day.
 

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Carbon buildup anecdote: I bought a 2015 Mazda 3 with the Skyactive 2.0 at a salvage auction a few years ago, so I have no idea how it was driven or maintained. The car had only 25k miles on it, and had been in a front end collision. Drove the radiator back into the intake manifold and cracked it (in addition to a lot of other parts, but that's another story). In any case, when replacing the intake manifold, I noticed a LOT of carbon buildup. I'm talking like 3x the buildup that zero-gravity showed in this thread. Chunks of carbon hanging on the walls, and a thick coating on the valve stem nearly all the way up to the valve seals.

In any case, I was on a deadline to get the car back on the road, and didn't have time to clean the valves. I put the car back together and we drove the car for a year before I sold it with all that carbon still on the valves, and maybe more. But maybe not much more, as I'm more rigorous about maintenance/quality oil, and most of our driving was longer highway trips of at least 30 minutes. I'd always intended to do the CRC spray, or even take it apart again and clean it by hand, but I never got around to it. The car always ran fine, and the fuel economy was fine: the wife got ~40mpg as she drives conservatively, I got ~32 because I drive like I stole it :devilish:.

So, I have to say that carbon buildup is a thing with DI engines, particularly if you do lots of short trips or use crappy oil that you run too long before changing. But at the same time, I have to confess that even the significant buildup that I saw still didn't create any noticeable effect.
 

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I have a 19 Mazda3 AWD with CD and have no problems. I had a few small first year problems that drove me crazy but were not big deals in hindsight.

My son drives my 15 Mazda3 with 100,000 miles and was perfect when I gave it to him. I see no reason it won’t run another 100,000 plus miles. I wouldn’t consider giving him my wife’s newer Subaru with less miles.

My daughter drives a 16 Mazda2.

All the Mazdas have basically the same engine and transmission. They have refined it over the years and it is as good as it gets. In my opinion.

None of the Mazdas have needed anything except basic maintenance. I actually think they would have been great even if we limited the maintenance to an oil change every 50,000 miles. Don’t try this it ain’t worth trying.

I buy Mazdas because I like the way they drive and because they are incredibly dependable. I don’t think there is anything more dependable on the market.

Look at the consumer reports ranking which reflects a similar opinion.
 

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Discussion Starter · #7 ·
Not sure about CD, but for DI it really isn't a problem. Many manufacturers use DI and have done so for years. It's been a rocky road, but overall they have it figured out now. Both Honda and Toyota use DI as does Hyundai. Ford does as well and has been playing with it for years.

Most modern DI uses an extra injector in the intake to get a bit of fuel on the valves. Mazda (to my knowledge) is the only one that solves it by heating up the valves. It's not perfect, but it's close. Carbon buildup that actually causes any problem is virtually unheard of. Might be an issue if you're only taking short trips in city.

I got curious and pulled the intake off to inspect and clean at 120k kms. Yes there was carbon, but not a lot. Cleaning it out made no difference at all. I documented here in a thread if you're curious.


On the flip side, I helped a good friend do the same job on his 2012 Hyundai accent which is also DI. That thing was a hot mess. So much oil in the intake it was rediculous. It was like a pile of black mud in there. It ran like a new car when we were done, but you know we will have to do it again one day.
I actually saw your posts while I was searching! They were really helpful. hopefully it's ok to not worry about any sort of valve cleaning unless I notice a reduction in performance?
 

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I actually saw your posts while I was searching! They were really helpful. hopefully it's ok to not worry about any sort of valve cleaning unless I notice a reduction in performance?
That was my exact conclusion. If there are no symptoms, ignore it. If you do have problems well so long as you can get a large compressor it's a cheap and easy tool to make. The walnut blast isn't expensive either.

Glad you got some use out of my posts. I was hoping someone would.
 

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Performance and fuel economy began to drop off in my 2014 2.5 cx5 at about 55k. I always figured it was due to carbon build up, but it could have been caused by lots of things. All factory recommended service was done on schedule. I traded it at 65k without ever knowing for sure what was the cause. It's not like it had a miss or was hard to start, unless you were very familiar with the car as I was, you would not know it was not performing as well as it once did so I got a good trade in price.
 

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The new gen Mazda 3 has a lot of unresolved annoying issues that Mazda simply can not fix. Read all the threads here on this forum and you will see a lot of frustrated people complaining about squeaks, rattles, a/c problems, software issues etc. The juice ain't worth the squeeze.
 

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I actually saw your posts while I was searching! They were really helpful. hopefully it's ok to not worry about any sort of valve cleaning unless I notice a reduction in performance?
Worry less about stuff w/ known, unpricey solutions(walnut blast). The minor issues the current gen owners bring up are nothing compared to CVT woes other makes give.
On my 7th year of Skyactiv ownership. Once you try 1, you'd welcome more. The work fleet currently has 4 Skyactivs, multiple buddies have 2 or more in their garages...All loyally in service, none have gone thru walnut. All solid & reliable.

Sent from my SM-G970F using Tapatalk
 

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The new gen Mazda 3 has a lot of unresolved annoying issues that Mazda simply can not fix. Read all the threads here on this forum and you will see a lot of frustrated people complaining about squeaks, rattles, a/c problems, software issues etc. The juice ain't worth the squeeze.
Read other brands forums and you’ll find lots of similar issues.
Do tell which brand you recommend?
 

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The new gen Mazda 3 has a lot of unresolved annoying issues that Mazda simply can not fix. Read all the threads here on this forum and you will see a lot of frustrated people complaining about squeaks, rattles, a/c problems, software issues etc. The juice ain't worth the squeeze.
You’d be right if the OP was looking for a 2019 3.

Issues were ironed out over the 2020 and 2021 models; I can attest to this having owned both a 2019 and 2021.
 

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The new gen Mazda 3 has a lot of unresolved annoying issues that Mazda simply can not fix. Read all the threads here on this forum and you will see a lot of frustrated people complaining about squeaks, rattles, a/c problems, software issues etc. The juice ain't worth the squeeze.

Orange juice ?
 
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