I mean, I’m a flawless master mechanic, too. The straps on these plugs are pretty brittle though. I’ve broken one myself and I had the ceramic on another plug crack on me. It was more of an admission of guilt than an attack. My bad plugs were my fault.
So initially the spark plugs were tightened in this engine by the Mazda mechanic who built my engine using a torque wrench. Or all 3 of them actually.
Then they were tightened by me in the parking lot but I'm still sensible and I kind of know how to tighten a spark plug, these are not the first ones that I've changed on my car. However,only with this engine I've had this problem.
I've gapped all the spark plugs on my car since 2011, so it's a bit weird that suddenly in 2019 I started doing something wrong, on 4 sets of spark plugs.
Let's just say we can safely rule out any spark plug tightening or gapping problem.
Although I was tempted to assume that all the NGKs I had were in an ultrasound storm then what was the catch with the Densos? They cracked even worse and nailed the last stud in this engine's coffin.
This whole thing about the cracking ceramic though is really weird.
It indeed, especially that first the ceramic insulator was cracking on the coil boot side, not inside the cylinder. So the "type 2" insulator breaking described here:
http://www.ngk-sparkplugs.jp/english/techinfo/troubleshooting/04/index.html
Also what they say there kind of makes sense:
Normally, deposits do not penetrate into this gap. If the engine overheats, the engine's cylinder head may distort. This means that cooling of the combustion chamber will fail which in turn means that knocking will occur more easily. Repeated knocking leads to abnormal pressure and vibration in the combustion chamber. This abnormal pressure and vibration causes the deposits that have accumulated in the combustion chamber to scatter as fine particles and enter gaps in the plug.
So I'm thinking that the engine was knocking quite a lot in other situations and this is what was affecting the spark plugs. During WOT pulls everything looked normal.
When logging the only situations when I was seeing quite a few degrees of retard were the usual ones, when cruising right at those loads and engine speeds when the knock sensor is and then is not listened to: 0.4-ish load, 2500-ish RPM.
Because of this I started to think maybe I had a problem with some of the injectors which were swapped at some point but did not make the problem go away: one of the sets was used and I sent for cleaning and flow testing, the second one was from my car the original set which I also sent for cleaning and flow testing to the same company.
Then it's the WMI. Maybe if one of the nozzles does not atomize properly then those drops can expand suddenly after the combustion occurs. If they end up in the spark plug area then they may be the cause for those deposits, just as well as the improper spray pattern of the DI injectors could be causing similar issues (but these were properly tested in a specialized facility though).
Then there's the CS cam shafts with the wider opening. Maybe these in conjunction with the Crower valve springs cause some harmonics or vibrations that lead to these issues shortly after a new spark plug is installed.
My biggest fear now is that I will rebuild the engine and end up with the same issue because of something else which I will put back on the car without knowing that caused the issues.
Right now I'm deciding between buying a fully built engine from SP63 or rebuilding the other block I have. My machinist just messaged me and told me that the old block can be bored to 88mm and used again.
) or I will need it for my CX7.
