I threw the timing light on the Blazer tonight and verified that the base timing was indeed set at 0 degrees (with the timing lead to the ECM disconnedted).

When I looked at the stock bin table, at 30Kpa and a 700 rpm idle ti shows 26.02 degrees. Is this what the ECM advances the timing to at idle? If so this seems a little excessive to me. Or am I interpreting the table wrong?

 

You need to subtract the bias value off. This may be as high as 20 degrees. Then again, it also depends upon which bin editor you are using along with which definition file. Some editors/files will sub the bias off for you.

My guess is that it isn't, check the timing with the light while the EST is connected.

RBob.

 

I did that, and the timing was off the tab! By extrapolation I figure that the timing at idle is about 14 degrees BTDC. The scale only goes from 0 to 8 degrees btw.

I was watching my IAC counts after checking the base timing and when the burbling quit and the idle slowed down to the commanded rpm of 700 they dropped from the low 40's down to the mid 20's. I'm sure that there is a connection somewhere, but for some reason it’s just not clicking yet. I’m sure that as I learn more my questions won’t seem so desperate.

P.S

I'm using Tuner Pro 4.13 and the 7747 mine.ecu along with a stock (starting over) AKAJ bin.

 

Look at the constant "Initial Spark Timing". The way I understand it that value should be the same value as the mechanical timing without the EST connected. If I am incorrect I am sure someone will correct me....

 

So if I understand what you are saying, is that with the EST disconnected, the idle timing should be o to 2 degrees BTDC? Then dial the timing curve in using the spark advance table?