Lumina V6-191 3.1L VIN T MFI (1993)
Electronic Spark Timing: Description and Operation
PURPOSE
To reduce spark knock (detonation) by retarding timing advance.
OPERATION
The Electronic Spark Control (ESC) system is comprised of a knock sensor and the ECM. The ECM monitors the ESC signal CKT 496 to
determine when engine detonation occurs. When the knock sensor detects detonation, the ECM retards timing in small increments of 2° (up to 10°)
to reduce detonation. This allows the engine to use maximum spark advance to improve driveability and fuel economy. Retarded timing can also
be a result of excessive valve lifter, pushrod or other mechanical engine or transmission noise.
