Electronics can break down, and maybe you did have a coil getting weak. Did you test the values across the terminals to see if it measured within spec? This is helpful info to have, as I've been noticing more people than usual with bad coils. Coincidence? or maybe the coils start getting flakey after 10-15 years. We've been noticing fuel pumps have been causing problems lately as well, so maybe coils are on their last legs at this point.

unless you've disabled closed loop, the AFV should be "correcting" itself, unless you have a out of spec O2 (or other) sensor providing false readings to the ECM. These can be tricky to ferret out, especially when a part is functional enough to work, yet malfunctioning just enough to cause a problem.