This guide explains how to properly set the throttle body stop screw (curb idle) to achieve the correct idle air control (IAC) position on drive-by-cable throttle bodies using Sniper, Terminator X, and Holley EFI systems. Start with the engine fully warmed up and verify your target idle speed. Then monitor the IAC percentage while adjusting the curb idle screw. The goal is to achieve an IAC position between 2–10%, with 3–5% being ideal. If IAC reads 0%, the throttle blades are open too far and must be closed slightly. If it’s above 10%, open the throttle blades slightly to bring it back into range. This ensures the IAC has enough control authority to maintain a smooth, stable idle.

A critical step in this process is ensuring the TPS reads 0% at idle. If throttle adjustments cause the TPS to rise above zero, the ECU exits idle mode and locks the IAC in a “hold” position—preventing further effective adjustments. When this happens, a TPS reset is required before continuing. Once dialed in, the engine should idle smoothly at the target RPM, even if the IAC passage is briefly blocked. Watch the full video for a step-by-step walkthrough and learn how to properly calibrate your system for consistent, reliable idle performance.