You're likely looking for one of two things:
* Base Timing: This is a starting point for the ignition timing, often set when the engine is first started cold. It's typically around 0-10 degrees BTDC (Before Top Dead Center), but this is a very rough estimate and can vary slightly depending on the specific ECM calibration. You cannot reliably determine this value without specialized tools.
* Ignition Timing Adjustment: You *cannot* adjust the ignition timing on this engine in the same way you would on a carburetor-equipped engine. The ECM controls it, and any attempts to manually adjust it will likely damage the engine or the ECM itself.
If you're having an issue with your 1999 Chevy Suburban's performance, do not attempt to adjust the timing yourself. Take it to a qualified mechanic who has a scan tool capable of reading the ECM data. They can diagnose the problem and determine if the ignition timing is indeed an issue. Incorrect timing will show up in the diagnostic trouble codes (DTCs) stored in the ECM's memory.
