Thanks to both responders so far. Those are great tests, and I do question the integrity of the harmonic balancer. I had read about the timing mark wandering under the strobe, and didn't see anything of the sort. That's when I stopped. I will try checking the piston head for TDC and verify crank mark and cam orientation.

If that tests correct I'll try pulling the sensor. The harness looked weak in a few places, and I've had an itch to replace it anyway. I did read in the 700 FAQ that if the coolant sensor feeds an overheat condition the ignition computer will advance timing to compensate. Has anyone tried this test before?

Thanks much-
Dylan