WHAT'S UP GUY'S. HERE GOES I HAVE A 91 Z28 CONV. I WAS TRYING TO SET MY TIMMING AND I DID IT THE WAY IT IS IN THE GM MANUEL. TURNED THE CAR ON DISSCONNECTED THE BROWN AND BLACK WIRE (PASSENGER SIDE). SET TIMMING TO 6 DEGREE
TURNED CAR OFF DISCONNECTED BATTERY AND PLUGED IN THE BROWN AND BLACK WIRE. THE DISTRIBUTER WAS TIGHTEN DOWN AND BATTERY WAS CONNECTED. WHEN I RESTARTED THE CAR THE TIMMING WAS ON 16 DEGREES. THE TIMMING WAS MOVING UP AND DOWN. SO I UNPLUGGED THE BROWN AND BLACK WIRE AND IT WENT TO 6 AGAIN. SO TRYED TO SET IT WITH OUT DISCONNECTING THE BROWN AND BLACK WIRE AND IT SET AT 6 BUT I DON'T THINK IT IS SET RIGHT. IT KEEPS MOVING UP AND DOWN AND WILL NOT STAY SET. HAS ANY ONE HAD THIS PROBLEM? AND MY CAR IS STILL RUNNING HOT. NEW TERMOSTA AND WATER PUMP. ENGINE IS 2 WEEK'S OLD ON REBUILD. FANS ARE WORKING. THANK'S

 

The movement of the timing (slightly) should be normal. As the RPMS increase, more advance is also added (done by the PCM). Now if it's steady w/out the connection made, your ignition system should be fine...if it bounces around TOO much with the connector on, then it's PCM related.