On the 2nd leg of a long cross country trip, I noticed that CHTs were running noticeably higher than usual on climb out.  After leveling off at 6,500msl, CHTs were uniformly running approximately 40+ degrees higher than normal.  Upon landing, the problem was eventually traced to one of my PMag ignitions that, was going to full advance at idle (39degrees). This was a failure mode of electronic ignitions that I hadn't considered before.  Given the engine seemed to be running fine otherwise, I didn't try switching off one ignition in flight, which likely would have pinpointed the problem.

 

Regards,

Clark Baker