I pulled the connector off one of my old ignition coils. The engine sound did not change much while in park (the rpm dropped to about 600), so I went in and shifted car to drive. Of course the entire car began to shake, so after 3 seconds I quickly put it back to park and turned the key off. As a result of this test, no misfires were stored in memory for affected cylinder and CEL did not appear (no pending codes either). I've repeated the same test again (same cylinder to activate "2 trip detection logic", but scanner again read everything as normal afterwards. This is why it is so difficult to pinpoint which coil is failing if miss is intermittent. BTW the CAT temperature was low during this test.
Tomorrow I'll put my last new coil and will report any significant changes.
(The idle quality is OK but lower than it used to be 4 years ago)

 

In the first few years of OBDII, any misfires would set a CEL light and code. (This, on many manufacturers' cars) <--- late 1990s

After many customer complaints, most manufacturers changed the threshold for code activation (some with software updates via TSBs) so that it took a greater number of misfires before the ECU would turn on the light.


So, that is why you are experiencing your issue.


That is also why I replaced all 4 coils at once when our Fit started seeing issues. (Didn't want my daughter to complain to Mom, LOL!)

 

Report so far:
The car did not transform into Corvette but up-shifts at lower RPMs now and shifts are not that hard;
The body vibration (not misfire, just vibration from engine running) is still present
I pulled the EGR valve; it was covered with some sort ow brownish deposits (not tar like stuff I saw on many older cars); the valve head had some ridge around its sealing flange.