Misfire caused by a misadjusted crank sensor (rubbing on flywheel)

Here, we’re diagnosing an intermittent misfire symptom, caused by an excessive crankshaft position sensor air gap. “Trash in, trash out” is how the saying goes, and this video is a perfect example. I’m also demonstrating the power of a lab scope, and the importance of verifying signal inputs before replacing parts.

Engine Performance Diagnostics chapter 21 page 20

Symptoms
- intermittent misfire
- no codes present

Fix
- adjust crankshaft position sensor air gap

Tests shown
- using an in-line spark tester to check for an ignition system issue
- checking an ignition coil primary current waveform with a lab scope and low amp probe
- checking camshaft and crankshaft position sensor waveforms for faults
- checking an ignition coil control signal (transistor external of the PCM)
- manually checking a crankshaft position sensor air gap

Tools used
- in-line spark tester
- Picoscope automotive 4 channel lab scope
- inductive low amp probe

Playlist
- (Chapter 21) Ignition inputs, cam and crank sensor
   • (Chapter 21) Ignition inputs, cam and...  

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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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