Timing jump at idle

[Bob Valentine]

I'm trying to figure out why my timing varies +/- about 4 degrees.    I've
flattened the table for several cells around in gear idle, 625rpm.  MAP
stays rock-steady at 35kpa.    Injector pw varies from 2.55-2.6ms.  The
idle is reasonably smooth no surging or misfire, but would be smoother with
the timing stable.

With the timing connector pulled and a timing light on the crank, the mark
stays even on 6deg.   The mark moves and follows the scantool with the EST
hooked up.  I changed the distributor (and module) since the one in the
motor had a slight bit of end play - no difference, same symptoms.   Plug
wires are routed as far from the harness as possible.    Disconnected the
alternator to rule out AC noise, no difference.  

Is this "normal" or is something going on?  

-> Bob Valentine
-> bob at tecmark.com

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