I'm looking around for some more detailed information regarding the IAC and idle spark control routines. I'm specifically dealing with a 1996 LT1 OS 16214399 which seems to have unpredictable idle quality when coming to a stop. Using TC, I have spent some time moving some of the dashpot tables around, softening the idle control PID, increasing and decreasing the mph threshold for idle control, however there still seems to be something else influencing the transition to idle that I can't figure out. Once the vehicle stops the idle is solid although a bit lopey (about 224@.050?). The fuel trims at idle and part throttle are within a few percent. The basic dashpot function and idle spark feedback tables appear to be fairly straight forward. What I'd like to understand with certainly, is how the ecu decides to go into closed loop idle control. Does the vehicle simply look to be below the vehicle speed threshold for idle control with the throttle closed, or is there more to it that that such as a MAP threshold? Possibly someone has disassembled this area of the code and can shed some light on this topic or would not mind sharing the disassembled code . Any input is appreciated.
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