I've just adjusted the timing on my 95 Civic (SOHC 1.6L PGM-FI). I
warmed it up to operating temp, jumped the 2P connector and checked the
timing at 750 RPM. Then I made the necessary adjustment.

I've had no problems with setting the timing, but I noticed something.
I had supposed that the jumper was there to stop the ECU from "messing"
with the timing, but that it was not necessary for *reading* the
timing. Of course I checked and adjusted with the jumper on just to be
sure, but I found that when the jumper is not connected, timing at 750
RPM is retarded by a several degrees.

Is this normal behavior? Can anyone enlighten me as to why it does
that?

Thanks in advance.