Post ignition coil observations

Maybe it's like a waxed car car goes faster, but I swear the mpg has gone up by a few.
For as much as a couple years, the car has had a slight miss at idle as evidenced by the exhaust having "bup" evey few seconds.
That's gone for at least now, and the rpm range has a more turbine-like smoothness. Also, it maybe just the contrast to my trusty old CRX Si I was driving all week, but the car pulls like a freight train.

I suppose the "bup" can indicate the eventual failure of a coil, and wonder if an analyzer can narrow it down to the cylinder. That'd be neat, as a preemptive changeout could be done way before failure.
But not like this:

"Ive just picked up a fault in the AE35 unit"



Edited 2 time(s). Last edit at 04/28/2024 05:15PM by Laz. (view changes)

The #5 coil might've gone because of heat stress from the loose pre-cat below it, but...
(and not definitively knowing what path exhaust gases take) there was no soot on the coil, nor any adjacent surface. With direct injection, quite a lot is produced, as evidences by the tail pipes. Perhaps air was being pulled in, causing the O2 sensor to "see" a lean condition, and enriching the fuel-air mixture, the result being a relatively high fuel consumption. With the tightened sensor, the system is taking proper readings, leading to the better mpg.