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

  1. #31
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    Quote Originally Posted by Go Hawks View Post
    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.

  2. #32
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    Quote Originally Posted by joemazdacx5 View Post
    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
    Last edited by Go Hawks; 05-04-2019 at 01:22 PM.

  3. #33
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    Arrow Dangerous cylinder deactivation trouble on 2018 CX-5 and 6 models

    Quote Originally Posted by yugrus View Post
    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.jpgMazda SkyActiv-G 2.5L Cylinder Deactivation_02.jpgMazda SkyActiv-G 2.5L Cylinder Deactivation_03.jpgMazda SkyActiv-G 2.5L Cylinder Deactivation_04.jpg

  4. #34
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    Arrow Dangerous cylinder deactivation trouble on 2018 CX-5 and 6 models

    Quote Originally Posted by Go Hawks View Post
    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!

  5. #35
    Registered Member yrwei52's Avatar
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    Arrow Dangerous cylinder deactivation trouble on 2018 CX-5 and 6 models

    Quote Originally Posted by COmtn View Post
    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

  6. #36
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    Quote Originally Posted by yrwei52 View Post
    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.jpgMazda SkyActiv-G 2.5L Cylinder Deactivation_02.jpgMazda SkyActiv-G 2.5L Cylinder Deactivation_03.jpgMazda SkyActiv-G 2.5L Cylinder Deactivation_04.jpg
    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.

  7. #37
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    Quote Originally Posted by yrwei52 View Post
    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.

  8. #38
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    Quote Originally Posted by Go Hawks View Post
    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!
    Last edited by shadonoz; 05-04-2019 at 05:06 PM.

  9. #39
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    Quote Originally Posted by shadonoz View Post
    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.

  10. #40
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    Arrow Dangerous cylinder deactivation trouble on 2018 CX-5 and 6 models

    Quote Originally Posted by shadonoz View Post
    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.

  11. #41
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    Arrow Dangerous cylinder deactivation trouble on 2018 CX-5 and 6 models

    Quote Originally Posted by Go Hawks View Post
    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.
    I thought Mazda has figured out what happened and came up a fix on PCM software. If they need your engine to research the problem in Japan, that indicates Mazda still hasn't figurd out what's going on to your engine and many others.

  12. #42
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    Quote Originally Posted by yrwei52 View Post
    I thought Mazda has figured out what happened and came up a fix on PCM software. If they need your engine to research the problem in Japan, that indicates Mazda still hasn't figurd out what's going on to your engine and many others.
    I agree. I feel they should recall all of the vehicles that have cylinder deactivation (CX-5 and 6), reflash the PCM, and do a visual inspection to make sure the rocker is in place at least. But it has been almost 6 months since my engine was replaced and I tried for a long time to ge them to recall and still nothing has been done. I guess my voice isn*t loud enough.
    Last edited by Go Hawks; 05-04-2019 at 07:04 PM.

  13. #43
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    so I have a 2019 sport cx5 , how would I try and replicate this failure
    what steps to try and follow ?

    have cx5 in sport mode or normal mode ?
    cruise control on ?
    what speed ?
    then what , just give it gas ?

    just wondering , If I should be complaining to mazda about 'CD' ..
    thanks

  14. #44
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    My guess is that some engines were not assembled correctly or bad parts were used, in order for a rocker to fall off. The spring tension will keep it in place. Maybe a spring broke. And it blows my mind that an engine can run with a rocker sitting under the valve cover somewhere and the valve stuck open. Did you hear any loud noise at any point come from the motor?

  15. #45
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    Quote Originally Posted by Go Hawks View Post
    I agree. I feel they should recall all of the vehicles that have cylinder deactivation (CX-5 and 6), reflash the PCM, and do a visual inspection to make sure the rocker is in place at least. But it has been almost 6 months since my engine was replaced and I tried for a long time to ge them to recall and still nothing has been done. I guess my voice isn*t loud enough.
    The PCM story can't be the problem. Maybe they are flashing it to disable cylinder deactivation.

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