Idle Speed Control (ISC)

The ISC is basicaly the choke for an EFI system although it works much differently. It controls how much air enters the engine when your not pressing the go pedel.
It bypasses air around the throttle plate.
It Controls idle speed.
Acts as a dashpot during deceleration preventing stalling.



The "IDLE IN GEAR" needs to be around 100 RPM lower than the "ISC MAXIMUM_CLOSED_THROTTLE_IDLE". If it is not then the timing is used to control the idle. My timing at an idle was moving all over the place until I had these parameter more than 100 apart. What I found was that the ISC was not able to control the idle due to the limit on the "ISC MAXIMUM_CLOSED_THROTTLE_IDLE" be lower than the "IDLE IN GEAR", which enabled the timing to control the idle. After adjusting the "ISC MAXIMUM_CLOSED_THROTTLE_IDLE" to 100 RPM's greater than the "IDLE IN GEAR" I found that I had a steady idle and a steady timing of 15 degrees.