I'm now thinking there may be a more pervasive electrical problem causing the Herky Jerky symptoms (chuggle). The system voltage always shows up kind of ragged in the scans. Take a look at this:
suspicions: Since events seem to be preceded by drop in road speed, could it be a sudden increase in drive-train resistance? Or, ref voltage effects on speed sensor?
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Does anyone know if this kind of fluctuation is normal on one of these GM CS-130 alternators?
Ed