[T3] Timing Light

[Daniel Nohejl]

Here’s a weird one: I went to use my timing light today to verify a few things and something strange happened. As always, I hooked the light up to the + side of the coil and grounded it where I always do. Suddenly, the engine started misfiring every few seconds and I couldn’t get any accurate readings. 

The light has the capability to read dwell, voltage, timing/advance, and rpm and the only sane reading I could get was of the dwell. The idle speed numbers were way off, the voltage danced around, and the timing was impossible to read b/c of the misfiring. As soon as I disconnected the light, everything went back to normal. Hooked it back up and the misfiring started. Disconnected the light and all was fine. Rinse and repeat.

So before I hit up a FLAPS to buy a new timing light, is it possible that the light is exposing some latent issue in my ignition system or does this sound like an open and shut case of a timing light going bad? 

FWIW, this is the light. I’d been burned on cheap lights before (inductive pickup stops reading, wires crack, etc.) so I shelled out for this one and, well, probably got burned after a year of use:

https://www.amazon.com/INNOVA-5568-Pro-Timing-Light-Tool/dp/B000EVU8J8/ref=cm_cr_arp_d_product_top?ie=UTF8