Using a KV tester
Using OTC's 3140 KV tester for quick Ignition diagnosis
89 Chev 5.7 TBI 79k Secondary KV off coil wire, meter mode of Tek THS710A. The plot would help for finding intermittents on the road under load. I am using this tester on the scope to provide images to show its benefit for KV tests. At the coil wire, (for enclosed coils, you will have to go on each individual wire) you will see the KV readings of all plug firings, go here first. Allow some time to get the lowest and highest readings, then you can go to the individual plug wires and view them to find the cylinders that are high or low.
In this case the high reading cylinder was number 4, the result of a open plug wire.
Most of the other cylinders were in this range.
These things are slick for quick tests on Secondary, on Dist, and DIS. Use them on your scope, or just a DMM with min-max feature. Sends mv/perKV signal.
See a case study on this Page.