I bought a timing light to check my spark timing; my vehicle is a 93' Mazda Miata and I am rotating the Cam Angle Sensor to advance or retard my timing. When I first used my timing light the engine was warm but not quite hot. I found out that my timing was retarded by about 3 degrees so I advanced it back to 10 degrees BTDC and took it for a test ride and after I got back I rechecked my timing and it seems to have advanced about 3 degrees so I retarded it back to 10 degrees. Now after the vehicle has cooled down I go again to test my timing and it seems like it is retarded back to where it was.
Now my questions are
why does the timing advance when the engine is hot? The rpm and engine load is the same so I don't think it has anything to do with that.
When should I adjust the timing? when it is hot or while it is warmed up?
When testing the timing while the engine is hot, the firing even seemed to be at a random angle every time like sometimes it was 12 others it was 14 does that signify anything?