Ignition Coil Diagnostics
So one of my coils did indeed frag earlier this year. it started out as a funky idle sometimes, clearing up with revs. then progressed to horrible loping idle, barely drivable home (thank god only two blocks away). I troubleshot by pulling first one coil wire off (U.S. 32-v has two coils) then the other. voila, found the dead side, ordered a new pair of coils and crossed my fingers.
Ohm tested per manual but surprisingly the suspected bad coil checked out. no matter, the car couldn't run and was reminded by the list that an ignition coil is not a resistor ;) Old coil makes nice paperweight once you clean it up.
Installed new coils and ta daa - one happy shark again. burned out coils are not uncommon to the 928, plus I was playing with some big plug gaps at the time so may have pushed the old ones to the limit and beyond, YMMV.
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