Oh, this’s the same guy who was relocating and had the higher compression on cylinder #4 with valve lifter ticking noise and camshaft damage? And now he has misfires in cylinder #2? I remember he replaced only the switchable HLAs on cylinder #4, and his current problem could not be related to the switchable HLAs he just replaced? ....
In the interest of fair and honest reporting, he never did follow up in that first thread to tell us how many HLAs were replaced, or even that the work was done at all. He did however mention in his second thread that HLAs were replaced, but not how many of them.
IMO the switchable HLAs used on cylinder #1 and #4 are designed to be activated and deactivated at certain oil pressures. Mazda then had to modified the oil pressures via the software to avoid the rocker arm falling issue during the recall. Having some problems on these switchable HLAs in the long run isn’t surprised me as these HLAs are operating in the oil pressure range which isn’t designed for originally.
Mazda didn't say anything in their TSB about the relationship of oil pressure to the switchable HLAs, and I'm not going to speculate about it either, because that particular factor is not important to me. What Mazda did say, and what is VERY important to me, is this:
Some vehicle may exhibit a tapping noise from the engine during idling; etc., and synchronized to the engine rpm. The tapping noise may be caused by the switchable hydraulic lash adjuster (HLA), which may not work properly due to air bubbles accumulated in the oil passage in it. To eliminate this concern, the switchable HLA has been modified for increased oil supply to reduce air bubbles in the oil passage.
So in publishing the above statement, Mazda admitted that the original switchable HLAs were not allowing enough oil flow. And that's what's really concerning to me - the fact that all of our older CD vehicles have HLAs identified by the automaker to have an oil flow issue, and which have been replaced in the newer engines with HLAs that (presumably) allow proper oil flow.
When I initially read about this, I figured let's wait to see what the future developments on this will be. I was hoping that perhaps the air bubble ticking noise is benign, and perhaps it might be possible to just live with it - that is up until Trzebs' thread showed up.
His experience indicates that there are likely to be significant physical side effects taking place beyond just the noise, and that these air bubble issues will almost certainly need to be addressed by replacing the HLAs. The jury is still out on this, and more data needs to arrive before a definitive conclusion can be reached. But this is going to be an uncomfortable period of wait and see - for me anyway.