In the field, a weak spark condition usually results in ignition coil replacement. However, there’s also the chance of an igniter issue causing poor saturation and prematurely limiting current flow in the coil windings. Rare, but possible, and it’ll burn you if you’re not aware of it. This is where the low amp probe and a lab scope shines during diagnostics.

Engine Performance Diagnostics chapter 22 pages 1025

Symptoms
intermittent stall, hesitation, misfire
intermittent hard start

Fix
replace ignition coil igniter

Tests shown
how to use an inline spark tester to identify an ignition issue
how to use a low amp probe to view a coil current waveform
how to use a lab scope to view a coil primary voltage waveform
analyzing a coil current waveform, identifying current limiting
using lab scope triggers during testing

Tools used
inline spark tester
Picoscope automotive 4 channel lab scope
inductive low amp probe

Playlist
(Chapter 22) No Spark Troubleshooting, Ignition Coil & Module Testing
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For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
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