As fare as I understand the IAC, it is actually a bypass for air from your intake to make it down in your engine. When you are idling your throttle plates are pretty much closed, but the engine still needs air, so the valve open ups the bypass to let more air in and keep the engine from dieing.

91 Trooper LS, 5 Speed Manual
3.4L Engine w/4.3L Throttle Body
Snorkel, 31" Pro Comp MT Tires, 2"lift,
ProComp ES9000 shocks and steering stabilizer

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