Mine was a loose/high resistance connector right on the negative side of the coil

Obviously looking at it , you sure in the hell couldnt tell when it had full insulation/rubber over terminal end

Didn’t figure it out until I took an ohm meter on the wire itself and had the wife wiggle and bend and move the wire around

And then when I finally took/peeled the insulation off you could see the dark area

Was a bad connection I would assume since new , as it progressively got worse over the years