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Wish they would just have a option to disable cylinder deactivation as I see zero MPG gains from the previous engine. Maybe they can fix the jerky low speed issue too.

Jun 27,2019
Manufacturer Recall Number 3719F
NHTSA Recall Number 19V-497
Recall Status Recall Incomplete, remedy not yet available

Summary

On certain subject vehicles, the powertrain control module (PCM) software controlling the hydraulic valve clearance adjuster may operate improperly when transitioning from cylinder deactivation to full cylinder activation modes while driving, due to inappropriate control logic of the PCM. As a result, an intake valve rocker arm may come out of position and make contact with internal engine parts, which may cause an engine misfire and loss of power and/or Malfunction Indicator Light (MIL) illumination.

Safety Risk

In the worst case, engine damage may occur, resulting in engine stall while driving without ability to be restarted, which may increase the risk of a crash.

Remedy

A Mazda dealer will reprogram the PCM with improved hydraulic valve adjustment control software, so that it may operate properly when transitioning from cylinder deactivation to full cylinder activation modes while driving.
 

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Ouch.

"Make contact"? Uh..... that would be called catastrophic engine damage.

One of the worst possible outcomes for a situation like this is valve/piston contact. That can and does, in many engines, lead to a valve dropping thousands of miles later on.

I hate to put this out there, as I love Mazda, but if I owned one of these vehicles I'd sell it NOW unless they are going to extend unlimited mileage warranty coverage against top-end failures including all consequential damage. IF you drop a valve like this it is highly likely to wipe out the engine entirely, and no, 60,000 miles is nowhere near enough coverage especially if you're halfway through the warranty period already -- which is likely for some of these vehicles.

Damn.
 

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I have not heard of a cylinder de-activation system out there, amongst all of the mfrs, that works trouble-free. I don't like them at all. Conceptually I don't like them. However good Mazda engineers are, when they came up with a de-activation system for a 4 cyl engine (the first such system) it REALLY gave me pause. I am not surprised. I hope for Mazda's sake this is not a mega-issue for them... (and for the owners, too, of course).
 

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Cylinder deactivation didn't improve gas mileage significantly, what was it 1mpg improvement on the highway?


What a waste of effort.
 

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It's not done for the window sticker number, it's done to satisfy the jackwads at the EPA and in Washington DC generally who keep insisting on more and more miles driven per gallon of fuel consumed.

You eventually run out of straight-line engineering ways to do that and have to resort to either tricks or deleting models since the "bin" is across your offerings; if you want to sell larger cars, which are of course heavier and have more frontal area (thus get lower fuel economy) you are forced into trickery of various sorts.

My view of the correct answer to this dilemma requires only about 3.5% of the American population to take the same decision, but it appears that what motivated people in 1776 here is long since dead, buried and forever gone.
 

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Man I can't find more info about this anywhere, those numbers return nothing on Google. To be fair though, it is only days old...
 

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I don't care which mfg. we're talking, I would never own a car with cylinder deactivation.

Never

The suggestion, while I'd bet money will never happen to have Mazda extend the warranty is a good one and the only thing that would help me sleep better at night.




.
 

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Reading this - this is no casual matter it would appear (and I'm not surprised). They speak of engine replacement if damage is found; no less than engine replacement 😐.
 

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We rented an F150 in Florida two weeks ago for work. Drove all over the state visiting multiple job sites. It's hot, like really hot (I'm from Michigan originally lol). The truck had cylinder deactivation which would cycle the A/C compressor off at each stop. What a terrible invention!


Fortunately, Ford had enough forethought to include a button on the dash you could press that defeated the deactivation "feature", but you had to remember to press it every time you started the truck. You would think Mazda could add a button to turn off the deactivation without too much trouble.
 

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Cylinder deactivation didn't improve gas mileage significantly, what was it 1mpg improvement on the highway?


What a waste of effort.
1mpg here, 1mpg there...do this for a few years and it adds up.

As cars become more and more fuel efficient, it becomes more difficult to significantly increase MPG with incremental improvements like adding cylinder deactivation.
 

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1mpg here, 1mpg there...do this for a few years and it adds up.

As cars become more and more fuel efficient, it becomes more difficult to significantly increase MPG with incremental improvements like adding cylinder deactivation.

If 1 mpg makes a difference better not drive, instead walk/cycle/public transit.

I can understand choosing a car that doesn't require premium fuel as some parts of the world that makes 50 cents/gallon price difference.
 

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@GWL -- It's not the buyer, it's the government that mandates minimum fuel economy standards across your fleet.

Yes, I understand, LeManSteve wrote, "1mpg here, 1mpg there...do this for a few years and it adds up."


Chrysler Hemi had issues with dropping valve seats for 2005-2007, like this the engine was too costly to fix.
 

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There's no real "fix" if you have valve train damage. The problem is that rockers don't break on their own. The break, typically, because the valve hits the piston and *something* has to give. The weakest thing does. IF that happens, however, there's hidden bad news. Frequently the bad news is that the valve stem is compromised. So you "fix it" and 10k miles or so later the valve stem fractures, the head drops into the cylinder, and destroys the engine.

This is why Mazda is replacing engines; they KNOW what is going to happen if they don't.

Thus if you EVER suspect valve/piston contact, for any reason, you remove the head and go through the whole thing. Well, that's expensive. So they don't. But if you have it happen to you out of warranty, well, you're screwed. If you can do the work yourself then the cost of the actual head work isn't ridiculous, but if not, then bend over because this is not cheap, at all.

Don't buy cars with this garbage. That's all.
 

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It seems to me that there was no great fan-fare about Mazda bringing-in this system, in 2018, to the normally-aspirated 2.5 litre engine. And, also, the pendulum-type flywheel that accompanied it - on the Auto Transmission. The manual transmission cars did not get this, only the automatics. To some degree, it seems like it was sprung on the market, and that people were un-aware.

Following this, I wonder how durable the A/T will be with that "innovation".

Mazda is wont to try new technologies, it seems.

Not saying that announcing this would have stopped most people... but for me, a Luddite, well you know the answer. Sorry, I like Stupid, Simple.
 

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Honestly, I'm not all that surprised. Cylinder deactivation is just another breaking point to the engine. Start-stop is another BS technology that doesn't do much but gives more anguish over the long term.

The reliability, efficiency, and power of modern engines are already very impressive, it's ridiculous all the gymnastics these automakers are trying to do to chase that 1 extra MPG.

This is one aspect where Toyota's conservative approach to new tech for improved reliability works in their favor.
 
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