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Dangerous cylinder deactivation trouble on 2018 CX-5 and 6 models

I still wonder how the engine runs fine in idle with dislodged rocker arm... And how the arm is allowed to slip on the shaft. Perhaps, that lateral movement is by design to shut the cylinder off by missing the valve. And increased oil pressure is supposed to bring it back over the valve.
Ok, I think it now makes sense, if that's the case. Rocker arm slipped to de-activate the cylinder on the highway, then there wasn't enough oil pressure to get it back over the valve when full power is commanded. Fuel is injected, but no combustion. PCM hits panic button, lighting up the dash and invoking limp mode.
On restart the PCM commands full oil pressure, the arm gets back over the valve.
The rocker arm literally falls off. It was laying down by the valve port. The engine runs fine during idle and lower RPMs due to the fact that it has four valves per cylinder. The computer only senses a problem at higher revs. At this point it senses a lean situation on #4 cylinder (in my case) because one intake valve is not stroking. This is what makes this situation so deadly. You as the driver have no indication or idea that you have a problem until you are reving the engine and need the power and suddenly the computer senses trouble and throws the engine into limp mode. As my first post indicated, it happened to us when we were passing an 18 wheeler at night. This is what I was, and still am so furious about. We as the drivers of these vehicles have no idea something is wrong untill it is too late. This happened months ago and I am bringing this up now again because I just took our car in for an oil change and talked with the service manager about all of this again. He stated that since my car left and one other one they had to change the engine in, there has been nothing from corporate about this situation. Total silence!! So I figured I would try to see if I could get the word out to people about this since there has been no recall or really any action from Mazda. I am concerned that there may have been people already in accidents or possibly killed due to this issue. This could easily cause a head-on collision and at that point people would just think it was driver error or ignorance not knowing that the cause was mechanical failure.
 
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2018 CX-5 GT PP
Here we go, to the previous discussion about cylinder de-activation. All this nonsense for what, like 0.5 mph gain at the right conditions?
What does this have to do with the CD feature? The OP stated he was driving in conditions where it wouldn't have been on. He's describing something very different. Misleading title.
 

yugrus

Contributor
:
CX-5 GT
I wholeheartedly thank you for this effort. Looks like the proverbial "don't lose your face" Japanese attitude. Rocker arm falling off completely, eh... If Mazda has registered in automotive scale of things, this would have been a scandal...
 

yugrus

Contributor
:
CX-5 GT
What does this have to do with the CD feature? The OP stated he was driving in conditions where it wouldn't have been on. He's describing something very different. Misleading title.
I don't think so. He was on the highway, following the rig. Steady high-speed, low RPM situation. Cylinder deactivation must have been on before the ordeal happened.
 
What does this have to do with the CD feature? The OP stated he was driving in conditions where it wouldn't have been on. He's describing something very different. Misleading title.
It during cylinder deactivation that the rocker arm falls off. So once that rocker arm is off you have a serious situation that you have no indiction of. A few days later you may be driving and need to pass a vehicle. At this point you accelerate and the RPMs hit about 5000 and all of a sudden your car goes into limp mode. You cannot rev the engine past approx. 2500 RPMs. Deadly scenario if your are stuck in the oncoming lane with oncoming trffic and no acceleration to get you out of the way.
 

yugrus

Contributor
:
CX-5 GT
Two rocker arms operate two intake valves. One falls off the shaft. Another one operates its valve in idle and low-power operation. Everything is cool and dandy. But when you request full power, it is nowhere to be found, because the second intake valve is closed shut.
 
Please, if you have one of these vehicles 2018 cx-5 or Mazda 6, your car has cylinder deactivation and you need to take it in and have them remove the valve cover and visually inspect to make sure all is well. And demand they reflash your PCM! The 2019s also have cylinder dactivation unless you have the Turbo engine. Remember, they told me that one of their two PCM suppliers has the wrong program. This means that it is possible that half of or maybe more than hal off all of these vehicles are driving around with this problem and people don*t even know it. Which means that even if you don*t drive one you could end up meeting one in your lane someday.
 
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Two rocker arms operate two intake valves. One falls off the shaft. Another one operates its valve in idle and low-power operation. Everything is cool and dandy. But when you request full power, it is nowhere to be found, because the second intake valve is closed shut.
This is exactly right. Now you understand what I am saying.
 
This is exactly right. Now you understand what I am saying.

Its sounds strange, but the rocker arm is not attached to anyrhing in this engine. It is *pinched* between the cam and the lifter at one end and the valve stem at the other. Any slop on either end allows for the cam lobe to peel the rocker arm off and throw it down.
 
bought a new 2019 beginning of april and not once has anyone from mazda said
anything to me about this cylinder de-activation. I didn't even know about it till
just now reading this thread !
I don't think I would have bought it had I known..... , same with getting
harley.. but you can activate/de-activate that on hd easily enough....
If you bought the grand touring reserve or signature model, your vehicle has turbo and no cylinder deactivation. All others do
Thought the engine was acting wierd when driving around town......slow speeds.
Thought is was just the gearing ........but it makes sense that it is the de-activation
kicking in .........

thanks op for making me aware of this....

Is there a website to view the service bulletin ?
If you bought the grand touring reserve or signature model then you have the turbo and no cylinder deactivation. All other models do
 
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yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg. Plano, TX
Contributor
:
Plano, Texas, USA
Two rocker arms operate two intake valves. One falls off the shaft. Another one operates its valve in idle and low-power operation. Everything is cool and dandy. But when you request full power, it is nowhere to be found, because the second intake valve is closed shut.
I was about to say that it must be just one of 2 intake rocker arms on cylinder 4 fallen off during cylinder deactivation cycle when the hydraulic lash adjuster releases its lock pin with low oil pressure. I still don't understand how the rocker arm simply would fall off the position during CD cycle, as oil pressure is supposed to be low to release the lock pin and disable the hydraulic lifter, and the rocker arm supposed to be still in position during such situation. I believe Mazda either didn't tell the truth to OP, or Mazda hasn't figured out the root cause of this problem. Again, like EPB TSB, this seems to be a hardware design issue, and it has nothing to do with software which controls the oil pressure. I doubt the "fix" on PCM firmware would truly fix this, just like Mazda's initial attempt of trying to change EPB control module firmware on 2016 CX-5.






Mazda SkyActiv-G 2.5L Cylinder Deactivation_01.jpg Mazda SkyActiv-G 2.5L Cylinder Deactivation_02.jpg Mazda SkyActiv-G 2.5L Cylinder Deactivation_03.jpg Mazda SkyActiv-G 2.5L Cylinder Deactivation_04.jpg
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg. Plano, TX
Contributor
:
Plano, Texas, USA
Its sounds strange, but the rocker arm is not attached to anyrhing in this engine. It is *pinched* between the cam and the lifter at one end and the valve stem at the other. Any slop on either end allows for the cam lobe to peel the rocker arm off and throw it down.
Wow, there's nothing to hold rocker arms in place? What a genius design!
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg. Plano, TX
Contributor
:
Plano, Texas, USA
What does this have to do with the CD feature? The OP stated he was driving in conditions where it wouldn't have been on. He's describing something very different. Misleading title.
One of the intake valve rocker arms on cylinder 4 which is the subject of disabled cylinders during cylinder deactivation cycle had fallen off but it didn't produce any CEL error code. The vehicle drives normally in low rpm but once the power is needed, the engine can't keep up and forces it to the limp mode. It's dangerous indeed under certain circumstances, especially the driver doesn't know there's a problem

The rocker arm won't fall off the position when the hydraulic lash adjuster is fully functional. Cylinder deactivation disabled the PLA with low oil pressure releasing a lock pin. But once it happens, the rocker arm potentially would fall off.

No, it has everything to do with Mazda's cylinder deactivation!

I hope OP had a picture posted showing a rocker arm is lying in bed of cylinder head ;)
 
I was about to say that it must be just one of 2 intake rocker arms on cylinder 4 fallen off during cylinder deactivation cycle when the hydraulic lash adjuster releases its lock pin with low oil pressure. I still don't understand how the rocker arm simply would fall off the position during CD cycle, as oil pressure is supposed to be low to release the lock pin and disable the hydraulic lifter, and the rocker arm supposed to be still in position during such situation. I believe Mazda either didn't tell the truth to OP, or Mazda hasn't figured out the root cause of this problem. Again, like EPB TSB, this seems to be a hardware design issue, and it has nothing to do with software which controls the oil pressure. I doubt the "fix" on PCM firmware would truly fix this, just like Mazda's initial attempt of trying to change EPB control module firmware on 2016 CX-5.






View attachment 220808 View attachment 220809 View attachment 220810 View attachment 220811
From what they told me, you are correct on the lowering of pressure to release the latch pin, but it still maintains some pressure on the lifter as to not totally drop out. If this pressure is too low, the lifter will fall too far and present a gap between itself and the rocker. This is just enough slop to allow the rocker to be dislodged. Supposedly the right programming makes sure there is the correct pressure to not allow this to happen.
 
One of the intake valve rocker arms on cylinder 4 which is the subject of disabled cylinders during cylinder deactivation cycle had fallen off but it didn't produce any CEL error code. The vehicle drives normally in low rpm but once the power is needed, the engine can't keep up and forces it to the limp mode. It's dangerous indeed under certain circumstances, especially the driver doesn't know there's a problem

The rocker arm won't fall off the position when the hydraulic lash adjuster is fully functional. Cylinder deactivation disabled the PLA with low oil pressure releasing a lock pin. But once it happens, the rocker arm potentially would fall off.

No, it has everything to do with Mazda's cylinder deactivation!

I hope OP had a picture posted showing a rocker arm is lying in bed of cylinder head * ;)

I do have the pictures somewhere in all of my paperwork. I will look for it later tonite and post if i find.
 

shadonoz

SkyActiv Member
Contributor
:
State of Jefferson
:
2017 CX-5 GT AWD+
I do have the pictures somewhere in all of my paperwork. I will look for it later tonite and post if i find.
Looking forward to them.
This is mind boggling.

Why would they have to rebuild the engine? Is a repair to the valve train too difficult/impossible at the dealers?
I'm having a hard time visualizing the rocker arm just floating around loose in the head!
 
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Looking forward to them.
This is mind boggling.

Why would they have to rebuild the engine? Is a repair to the valve train too difficult/impossible at the dealers?
I'm having a hard time visualizing the rocker arm just floating around loose in the head!
When my car did this Mazda corporate was wanting all engines experiencing this issue sent back to Japan. So they replaced my engine. Not sure how they will handle it now. And yes, it had fallen off and was just sitting there.
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg. Plano, TX
Contributor
:
Plano, Texas, USA
Looking forward to them.
This is mind boggling.

Why would they have to rebuild the engine? Is a repair to the valve train too difficult/impossible at the dealers?
I'm having a hard time visualizing the rocker arm just floating around loose in the head!
If the rocker arm can be easily falling off the position when the oil pressure to hydraulic lash adjuster is low releasing the lock pin, and the updated PCM firmware has raised the oil pressure to solve issue, why can Mazda simply just put the rocker arm back for a much simpler fix? I suspect there's more involved and Mazda has to use a new engine hoping the same problem won't happen again.
 

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