Hey guys,
We have finally decided that we are going to replace the 4Runner with a Mazda CX-5. We went to a dealer on Sunday, and should be picking one up this week once we get everything in order. However yesterday afternoon I was at a filling station, and up pulled a woman in a CX-5, so I asked her how she liked the car. She said she loved it, but has had a few issues. Most alarmingly she said that Mazda replaced her engine after it failed. She wasn't very technical about the problem, but mentioned that she looked it up after the car died on her one day, and found it was a problem with the rocker arms. I did a little google search, and it appears that Mazda is/has recalled the 18 and 19 models for issues with the cylinder deactivation system. Should we be concerned about this? I am a pretty loyal Mazda guy, and know of a CX-5 with over 300k miles on the original engine, but it is a 15 model year. I know it's under warranty for a while, but we tend to own cars a long time, and I'd hate to buy a car with an unreliable engine.
Yes, you should be. I had no idea Mazda was doing that, but GM, Chrysler, Honda, and someone else have that tech, and they are all being sued over it.
We haven't finalized the deal yet. Should I not do it? I'm reading about a lot of issues with this that sound downright dangerous. Seems Mazda said it was a software problem, but digging deeper it seems like a bigger issue with the rocker arm falling out of position, and failing at higher rpm's when you are least expecting it.
I had no idea they had cyl deactivation, they only have 4 clys in that car...
fidelity101 said:
I had no idea they had cyl deactivation, they only have 4 clys in that car...
Apparently the CX-5's prior to 18 don't have CD, and the turbo engines don't have it at all, but the 18/19 N/A have CD. I'm getting nervous about this. Apparently there have been several engines where the rocker arms fall off on cylinder 4, and you don't realize it until you really rev the engine(like trying to pass someone), and the engine goes into limp mode. Mazda did a re-flash of the ECU to keep the oil pressure higher so as to keep the HLA(hydraulic lash adjusters) from collapsing, and and allowing the rocker to fall out of position. Problem is the rocker could fall off at any time ,and you won't know about it unless it falls somewhere that it's hitting something else. Mazda's fix I read is engine replacement if the rocker falls off, but that doesn't fix the design problem of the rocker that can still fall out (in my opinion). Maybe I'm worrying about this too much, but I don't really want to drop a bunch of money on a car, and then have to deal with engine troubles. It's the reason I'm buying a new car, to avoid car troubles.
I just read up about this a little, since my wife's 2018 CX-5 went in for an oil change last week and they performed recall work. From what I'm reading, when the deactivated cylinders come back online, the rocker could make contact "with other engine parts" (whatever they may be) and this causes the issue. With the ECU reflash, it changes when and how the cylinders come back online to avoid this. I would think that anything new would get the reflash before delivery, so it shouldn't be an issue.
Put it this way: my wife has put 25k on hers so far, and she drives it like it's a Spec Miata at full tilt most of the time. It hasn't blown up yet.
Tony Sestito said:
I just read up about this a little, since my wife's 2018 CX-5 went in for an oil change last week and they performed recall work. From what I'm reading, when the deactivated cylinders come back online, the rocker could make contact "with other engine parts" (whatever they may be) and this causes the issue. With the ECU reflash, it changes when and how the cylinders come back online to avoid this. I would think that anything new would get the reflash before delivery, so it shouldn't be an issue.
Put it this way: my wife has put 25k on hers so far, and she drives it like it's a Spec Miata at full tilt most of the time. It hasn't blown up yet.
I get that Tony, but what if that one time she's passing some slowpoke on a back road, and then the car goes into limp mode and she can't make it, causing a wreck? The whole rocker arm falling off thing is bothersome. I guess it doesn't even really give you a warning before it happens either. Kinda scary.
I think the answer is this "Honey we need to get a turbo one so the engine doesn't explode".
Aaron_King said:
I think the answer is this "Honey we need to get a turbo one so the engine doesn't explode".
If only that was in the budget.
In reply to Mazdax605 :
What I don't get is how it's just falling off. It has to make contact with something else to incur damage and break off, which is why they performed the reflash. Not saying that it won't happen with another one (or even ours), but I've hammered on ours just about every time I've driven it and nothing has happened in 25k miles of driving.
Tony Sestito said:
In reply to Mazdax605 :
What I don't get is how it's just falling off. It has to make contact with something else to incur damage and break off, which is why they performed the reflash. Not saying that it won't happen with another one (or even ours), but I've hammered on ours just about every time I've driven it and nothing has happened in 25k miles of driving.
Apparently the fall off because the only thing holding it in place is the HLA, and if it is collapsed due to low oil pressure(like every time you start the engine) the rocker can fall out because it is not locked in place by anything. Seems like a poor design, but not exclusive to Mazda.
Is there a way to get it deactivated in the cars ECU?
Aaron_King said:
Is there a way to get it deactivated in the cars ECU?
From what I've read so far, no it can't be deactivated, and even if it could I think the problem really lies with the rocker arm design, but I don't know that really.
Vigo
MegaDork
8/27/19 1:10 p.m.
I mean it sounds to me like "If you don't notice that 25% of your engine stopped working and then get into a situation where you need 100% of your engine you're gonna have a bad time". Knee jerk reaction to that is notice when your engine stops working properly. The chucking rocker arms out thing occurs on a variety of engines due to falling valve seats, cracking valvesprings, overheating valves due to poor seal or improper mechanical lash, etc etc. I mean yeah, it'd be nice if they designed it to not be able to fall off but i wouldn't say the ability to fall off during a mechanical failure is even a rare trait.
I think a used turbo at the same price as a new NA might be a good solution here. OR just not worry about it. The thought of the engine having 25% less power than it needs in an emergency situation sounds like a sales pitch for the turbo anyway. The turbo minus 25% is still more than 100% of the na. 
Have any of the manufacturers gotten this down? I remember earlier this decade GM trucks/cars having huge issues with stuff relating the CD.
I'm not a mechanical, or automotive engineer, but instead of doing all this wild stuff while the cams/rods/pistons will still be rotating.........just have the computer kill the fuel/spark to a few cylinders? Seems much more simple than playing with lifters and all that.
But again, I have no design experience in this so I'm sure it's much more difficult than what I'm thinking.
Vigo said:
I mean it sounds to me like "If you don't notice that 25% of your engine stopped working and then get into a situation where you need 100% of your engine you're gonna have a bad time". Knee jerk reaction to that is notice when your engine stops working properly. The chucking rocker arms out thing occurs on a variety of engines due to falling valve seats, cracking valvesprings, overheating valves due to poor seal or improper mechanical lash, etc etc. I mean yeah, it'd be nice if they designed it to not be able to fall off but i wouldn't say the ability to fall off during a mechanical failure is even a rare trait.
I think a used turbo at the same price as a new NA might be a good solution here. OR just not worry about it. The thought of the engine having 25% less power than it needs in an emergency situation sounds like a sales pitch for the turbo anyway. The turbo minus 25% is still more than 100% of the na.
Actually Vigo I think the problem lies with not 25% of the engine not working, but rather one valve of the 4 on that cylinder isn't working which doesn't rear its ugly head until you give it the boots. So in other words 50% of that intake on that one cylinder is not working. But to compound this the ECU doesn't do anything about it until you really need the power, and then it goes into limp mode with little to no warning. Maybe I'm wrong but that is what I've gleaned so far.
z31maniac said:
Have any of the manufacturers gotten this down? I remember earlier this decade GM trucks/cars having huge issues with stuff relating the CD.
I'm not a mechanical, or automotive engineer, but instead of doing all this wild stuff while the cams/rods/pistons will still be rotating.........just have the computer kill the fuel/spark to a few cylinders? Seems much more simple than playing with lifters and all that.
But again, I have no design experience in this so I'm sure it's much more difficult than what I'm thinking.
Just passing air through cylinders would not help- the big gain on this technology is to reduce the pumping losses, but if you keep pumping those cylinders, then you still get the pumping losses with no power gains. The deactivated valves allow the cylinder to be a spring, which is largely power neutral (not exactly, but not bad). Let alone the massive problem it would have with the emissions.
For sure, it it were that easy, everyone would have been doing it for decades.
Vigo said:
I mean it sounds to me like "If you don't notice that 25% of your engine stopped working and then get into a situation where you need 100% of your engine you're gonna have a bad time". Knee jerk reaction to that is notice when your engine stops working properly. The chucking rocker arms out thing occurs on a variety of engines due to falling valve seats, cracking valvesprings, overheating valves due to poor seal or improper mechanical lash, etc etc. I mean yeah, it'd be nice if they designed it to not be able to fall off but i wouldn't say the ability to fall off during a mechanical failure is even a rare trait.
I think a used turbo at the same price as a new NA might be a good solution here. OR just not worry about it. The thought of the engine having 25% less power than it needs in an emergency situation sounds like a sales pitch for the turbo anyway. The turbo minus 25% is still more than 100% of the na.
For the record the turbo engine doesn't use cylinder deactivation(CD).
alfadriver said:
z31maniac said:
Have any of the manufacturers gotten this down? I remember earlier this decade GM trucks/cars having huge issues with stuff relating the CD.
I'm not a mechanical, or automotive engineer, but instead of doing all this wild stuff while the cams/rods/pistons will still be rotating.........just have the computer kill the fuel/spark to a few cylinders? Seems much more simple than playing with lifters and all that.
But again, I have no design experience in this so I'm sure it's much more difficult than what I'm thinking.
Just passing air through cylinders would not help- the big gain on this technology is to reduce the pumping losses, but if you keep pumping those cylinders, then you still get the pumping losses with no power gains. The deactivated valves allow the cylinder to be a spring, which is largely power neutral (not exactly, but not bad). Let alone the massive problem it would have with the emissions.
For sure, it it were that easy, everyone would have been doing it for decades.
Gotcha, for some reason I wasn't thinking about the fact the cylinder would still be compressing air (and not making power out of it).
This sounds interesting, I'm bookmarking this so I can read up on how the system works tomorrow, if I have time.
I wonder if it's like the DOHC Neons where when the oil pressure would drop during high RPM use (well, technically there'd be full pressure of foam), the higher lash due to the collapsed HLA would cause the center of the rocker to break out and turn into a camshaft-operated valve keeper removal tool. Which didn't end well at all.
It sounds to me like Mazda is using a collapsing HLA like GM's DOD, and since OHC rockers are usually retained by nothing other than a little cup that sits over the HLA, I can see how this could result in badness.
What I don't see is "engine goes into limp mode". Generally there is no such thing as "limp mode" other than when the electronic throttle control throws its hands up and gives you 15%. Most likely, the engine is giving you "just sucked a valve and now E36 M3's all busticated" mode.
In reply to Knurled. :
Either way, given the lawsuits that are against everyone who sells them, it seems to be a cycle beater vs. something the customer really can appreciate. Especially when it's the EU basic cycle.
If you got 10% more fuel economy, it might be worth the money. And if you got 15%, it might be worth the money and the lowered reliability and crappy driveability. But I can assure you that neither is possible with standard "displacement on demand" and isn't really possible with the new DOD system that GM now has, where the off cylinders cycle around. I would avoid it at all costs....
In reply to alfadriver :
I have disabled DOD on a couple GMs, no fuel economy difference was noted. I don't know if this is because the DOD is only good for getting economy on the test loop, or if the people driving the trucks instinctively give it more throttle to keep kicking it back out of V4 mode.
Confession: Part of the reason I like the idea of an LS4 swap is that I want to play with DOD, just to tinker.
alfadriver said:
In reply to Knurled. :
Either way, given the lawsuits that are against everyone who sells them, it seems to be a cycle beater vs. something the customer really can appreciate. Especially when it's the EU basic cycle.
If you got 10% more fuel economy, it might be worth the money. And if you got 15%, it might be worth the money and the lowered reliability and crappy driveability. But I can assure you that neither is possible with standard "displacement on demand" and isn't really possible with the new DOD system that GM now has, where the off cylinders cycle around. I would avoid it at all costs....
Avoid the Mazda CX5, or CD on anything at all costs?
What's funny to me is I asked about the Mitsubishi Outlander (GT V6) a few years ago and basically everyone said that it was worthless and old school and to avoid. I liked that it was simple and an older proven drive train. Now this isn't saying that a Mitsubishi is a good choice, but I don't think it's a terrible choice compared to these troubles.
Knurled. said:
This sounds interesting, I'm bookmarking this so I can read up on how the system works tomorrow, if I have time.
I wonder if it's like the DOHC Neons where when the oil pressure would drop during high RPM use (well, technically there'd be full pressure of foam), the higher lash due to the collapsed HLA would cause the center of the rocker to break out and turn into a camshaft-operated valve keeper removal tool. Which didn't end well at all.
It sounds to me like Mazda is using a collapsing HLA like GM's DOD, and since OHC rockers are usually retained by nothing other than a little cup that sits over the HLA, I can see how this could result in badness.
What I don't see is "engine goes into limp mode". Generally there is no such thing as "limp mode" other than when the electronic throttle control throws its hands up and gives you 15%. Most likely, the engine is giving you "just sucked a valve and now E36 M3's all busticated" mode.
I think from what I've read with the limp mode is that a rocker arm has fallen out of position (but not making any noise). Now you have 1 intake valve on that cylinder is not operating. At low rpms/loads the ECU doesn't see this as a problem. Now you give it the boots getting on the freeway, or passing someone on a two lane road. Now the ECU sees that cylinder is only half working and throws it into limp mode as it doesn't know why one cylinder is not working properly, but it knows that it is. There are pictures I've seen on threads regarding this of an otherwise perfectly fine rocker arm sitting in the bottom of the head minding it's business.
