COP Power Balance Test

Insight please. I've done power balance tests on computer controlled COP secondary ignition systems simply by momentarily unplugging the harness connector from each coil to find the problem cylinder. However, I last week purchased "The Hands On Vehicle Testing Reference" from AES Wave. In the book the author states that while it is ok to unplug the connector with the engine running, he stresses to NEVER "replace this harness with the engine running as a resulting voltage surge could spike the computer." The author states that after removing each connector shut the engine off, then replace the connector, then restart the engine and go to the next connector to disconnect. Have I been doing this incorrectly and risked a voltage spike to the computer by unplugging each connector and reconnecting with the engine running?

Nope, you're fine. That is typical book type information. Think about the almost 400v primary spike that is occurring in these coils. How does unplugging it cause more of a spike than that?!

Thanks for the response. I kind of suspected as much. Kind of like the old "Never use a test light on a computer circuit."

Yeah, that stuff still gets perpetuated among technicians, even today.