While reading the FSM,I noticed they talk about an open or closed circuit when doing diagnostics, what do those terms mean? Also the reasonI was checking them is that the 92 LT1 started missing at low RPM, in 6th gearyesterday, but did not show any codes this morning.any advise would be appreciated.

 

They were probably referring to open or closed loop. When your engine is started cold, it is in open loop. After coolant temp reaches operating temp and O2 sensor reaches approximately 600 degrees, it is supposed to go into closed loop. In closed loop, the ECM leans out fuel pulse width, so the engine will be more efficient by watching O2 readings, coolant readings, MAT readings.