I have seen many references to the benefits of advancing the timing on the 1.9l engine, so I decided to try it.  I found that if I advanced the timing at all, the idle would start to surge (jumping between about 1000 RPM and 2500).  Any ideas?

Some related info:  I have had a problem with the idle being rough.  The engine runs ok (passes emissions with more margin than any other car I have owned) but sounds kind of like it has a "hot" cam.  While setting the timing, I noticed that the timing would vary by a degree or so, several times a second.  I disconnected the idle stabilizer and adjusted the idle speed to spec (it dropped significantly and the timing variation stopped when I disconnected the stabilizer)  When I re-connected the idle stabilizer, the idle speed was right and the timing variation was gone.  I wonder if I have a bad idle stabilizer.

Bill