Thread: Ignition timing jump when checking timing with light.
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Old 10-25-2011, 09:34 PM
Wags391 Wags391 is offline
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Question Ignition timing jump when checking timing with light.
1992 S10 Blazer, 4.3L, 4x4, TBI (Z)

I was checking my timing with my timing light tonight, and I noticed that it has a little jump in it every couple of seconds. The timing mark would be dead on for a bit, then jump. I couldn't tell if it was jumping advanced or retarded, but it wouldn't not stay on TDC consistently for over 10 seconds. What could be causing this? I assume it has something to do with the ECM controlling the spark, but what would make it go off like that?

Thanks,

Jason
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