Violent engine shake

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18 CX-5
It's been 4 months since I courageously gave 2018 CX-5 a try, thanks to the encouraging feedback from users like Xeler8ing, Anchorman, and more, withh their assurance that the second generation CX-5 can be trouble free at least for some car owners. Indeed I'm very happy with the car so far.

I wanted to thank other members like yrwei52 too for cautioning others about the potential issues with cylinder deactivation. It's always better to be aware and to keep an eye. In fact my eyes are wide open in this regard. lol

One incident worth mentioning is perhaps a ONE-TIME violent shake of the engine at a traffic light. Car was in D and stopped using foot brake. Car was shaking so violently (as if it were resonating with source of excitation) that my wife thought I was playing with the brake! Never experienced such on the 15 or 16.5 CX-5 at all!

My first thought/fear was CD, but then dismissed the idea later because the problem never occurred again. (Assumption: if it were carbon deposits due to CD I guess the problem wouldn't go away, right?)

The second suspect, still my current theory, is the fact that the section of the road happens to be sloped, though very gently. Google search reveals similar experience of engine shake when car is resting on an inclination, although most people reported that it happens when car is uphill. In my case it was downward dip, so I'm not 100% comfortable to conclude my experience is "normal" yet. Still a mystery.

Anyone with similar experience with their 2nd gen CX-5?
 
My new CX-5 is barely older than yours and never exhibited the problem that you described. Cylinder Deactivation seems to work very well, despites what yrwei52 says.
 
Mazda CD comes on between 25mph and 50mph under light loads. Think about 1100 RPM in 5th. For those with gen1 this is flat steady state 30 mph. I am beginning to think this is an extremely conservative system which wont show any gains to 90% of drivers but those who know might be able to get 2mpg benefit. Take your car to the dealer. We have all had that one moment. Mine was when 4 lights came on and never had an issue again wrt it.
 
I wanted to thank other members like yrwei52 too for cautioning others about the potential issues with cylinder deactivation. It's always better to be aware and to keep an eye. In fact my eyes are wide open in this regard. lol
Actually the drawbacks of cylinder deactivation is well documented. It*s mainly on long-term reliability issues. I keep my cars forever that*s why I have concerns on CD and canceled my plan getting a new 2018 CX-5 due to the sudden introduction of the CD by Mazda.

I also prefer simplicity instead of complexity. CD, like turbo, increases complexity. You have more probability of failed or unstable components in CD system which may cause violent engine shake at stop light like you*ve experienced. Newly introduced software/firmware related to CD would have bugs which could cause the issues like yours or some other 2018 CX-5 owners have been experienced with sudden rough idle at the stop light.

One incident worth mentioning is perhaps a ONE-TIME violent shake of the engine at a traffic light. Car was in D and stopped using foot brake. Car was shaking so violently (as if it were resonating with source of excitation) that my wife thought I was playing with the brake! Never experienced such on the 15 or 16.5 CX-5 at all!
With several other similar reports from 2018 CX-5 owners I suspect your problem very likely is cylinder deactivation related. You should report this to your Mazda dealer at your next stop, which will help Mazda to aware this issue and come up a solution however this issue seems minor at this time.

Anyone with similar experience with their 2nd gen CX-5?
Here*re a couple of recent reports on rough idle at the stop light from 2018 CX-5 owners:

Brand new Mazda - Has Rough Idle - feels like it needs a tune up

2018 mazda CX5 vibrate
 
So it's not just me getting this. Thanks! Could it be also due to a different suspension design in the new CX-5 that rough idle tends to be more noticeable, and in some cases amplified (back to the inclined slope theory)? I'm hoping any CD symptoms, if what I've experienced indeed falls under that category, would not show up so soon, after only months of ownership. I thought you also mentioned CD damages are more to do with long-term reliability.
 
45,000 miles on my CX5 touring and never had a "violent" engine shake. ed

To clarify, other than that SINGLE one-time incident where the engine shake was reminiscent of an engine stall just about to happen, I have no complaints about the 2018 CX-5 at all. Yes I can sometimes feel the engine while car is idle, but the experience is at par with the first generation CX-5 (whether 15 o 16.5), no difference.
 
So it's not just me getting this. Thanks! Could it be also due to a different suspension design in the new CX-5 that rough idle tends to be more noticeable, and in some cases amplified (back to the inclined slope theory)? I'm hoping any CD symptoms, if what I've experienced indeed falls under that category, would not show up so soon, after only months of ownership. I thought you also mentioned CD damages are more to do with long-term reliability.
My concern of long-term reliability issues from cylinder deactivation are well documented issues such as premature wear on position rings, fouled spark plugs, and excessive oil consumption. But your issue could be caused by newly introduced software/firmware bugs for CD, or any new CD components which's unstable or failing. Any new components could always introduce new issues if it's not been tested thoroughly. A recent example is new hydraulic engine mounts introduced to gen-2 CX-5, which caused major engine shake in sub-zero temperature.
 
45,000 miles on my CX5 touring and never had a "violent" engine shake. ed
Yeah, we haven't seen any reports about rough idle at the stop light from 2017 CX-5 owners either. That's why I feel the problem could related to cylinder deactivation which is introduced to 2018 CX-5.
 
Huh, had no idea that the 2018 had cylinder deactivation. I have a 2013 and I got to drive my mother in laws 2018 for three days. Never noticed it turning on or off.

My 2017 Honda Odyssey on the other hand, holy crap! I got really annoyed with the vibrations and noise, as well as a noticeable delay in power. Found all of the 2011-2013 horror stories of failed piston rings, fouled spark plugs, etc on Odyclub. Newer models needing new motor mounts after 60k miles. I installed the VCMTuner on my Odyssey and it drives like a brand new car and handles so much better. Works by putting a resistor in line with the coolant temperature sensor. The temperature reading is lowered just below the threshold that would allow cylinder deactivation (or as Honda calls it VCM).

Odyssey is a whole different animal as it has a V6 though. I wonder if the CX5 could be fooled by a similar trick with temperature reading to not allow the cylinder deactivation (not that I would recommend it by any means on the CX5 at this point, lol!).
 
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Huh, had no idea that the 2018 had cylinder deactivation. I have a 2013 and I got to drive my mother in laws 2018 for three days. Never noticed it turning on or off.

Same observation, ride is very smooth, can't feel any deactivation or re-activation at all. Also, it's been several months since the "violent" shake reported here, so it's pretty safe to assume it' a one-time experience only. I'm still convinced it had to do with that sloped ramp from the shopping mall where my car stopped. Also, it's probably my poor command of English, by "violent" I actually mean "very noticeable". Hope my inadvertent exaggeration has not discouraged prospective 2017/2018 buyers. As mentioned I'm very happy with the car.
 
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