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I'm speculating, but the following makes sense to me. The figure below is a revised (by me) version of a figure from the patent. I suspect that the oil pressure variations involved in operating the locking pins in the HLA have the unintended side effect of interfering with the free flow of oil...

Oil pressure isn't what holds the lifter against the rocker. The large, axial-acting spring inside the HLA is what forces it into contact with the rocker. The conventional function of a hydraulic lifter in regulating (setting to zero) the rocker-to-valve clearance is still present in the...

Although the engine-wide oil pressure is regulated in response to a lot of engine parameters, the oil pressure change seen by the HLAs that turns CD on/off is controlled by a couple direction switching valves (number 46 and 47 in the schematic at figure 4). Here's a picture of those valves. I...

I found Mazda's patent (US20150377151A1) that describes the cylinder deactivation mechanism. Like any patent, it's not light reading, and there's an extra layer of difficulty because it's been translated from the original Japanese. However, if you're willing to slog through it, you'll get a very...

I'm not sure any of us completely understands how the HLAs work when switching between normal and cylinder deactivation modes. So I'm open to the possibility that the following reasoning is flawed, but here's how I see it. What little CD documentation exists online (see this page) describes a...

Those posts are about the feasibility of coming through the oil fill opening in the valve cover with a scope to look directly at the rocker arms. My idea is to remove the spark plug, stick the scope into the spark plug hole, and view the movement (or lack of movement) of the valves inside the...

Rather than having to remove the valve cover, wouldn't it be possible to use an endoscope or borescope (kind of like this) through the spark plug hole to check that both valves are opening? If its rocker arm is off, the valve will be closed when the other one is open.

Some people might have missed where the OP mentioned in his initial post that Mazda had confirmed 26 similar occurrences.

Actually, it [the rocker] relies on 3 points of contact at all times: valve, cam, and HLA. I don't see how oil pressure figures into keeping contact between the rocker end (at the HLA) and rocker roller (at the cam). Look at the diagram at the link in my previous post. There's a substantial...

I don't understand how low oil pressure could be the cause of the rocker arm falling off. If it was, wouldn't the rocker arm be likely fall off each time the engine is started, since oil pressure is essentially zero for the first turn of the camshaft? There's a drawing and explanation of what...