AEM 30-6905 Universal Programmable EMS-4 - Manual (Page 157)

Page 157 of 279 EMS-4 Install and Tuning Guide_Rev 1.6
High Idle RPM Offset Units: RPM, Description: The additional amount of RPM added anytime
the system goes into idle control. The RPM is added for the length of time specified in the Hi
Idle Wait Time option. This function is also used anytime the car is below the High Idle Above
VSS Value.
Idle RPM Trim Start Units: RPM, Description: Additional RPM added when the engine starts.
Uses the RPM Offset vs Start table to determine decay time.
Ign Trim Idle Units: Ignition Degrees, Description: Additional amount of ignition timing added or
subtracted that comes directly from the Ign Offset vs RPM table during idle condition.
Idle Tuning Procedure
The first step before tuning the IAC system is to determine the direction of the motor. The
language of the IAC motor is in percentage. This is not percent open or percent of airflow, it is
rather the full-scale percentage of the motor where 100% may be fully closed or fully open. Do
not assume that a larger idle percent gives a higher idle speed. Some factory units actually
decrease Engine RPM as idle percentage increases. It is very easy to determine which way
your specific IAC system works.

Open AEM Tuner and connect to the EMS.

Confirm that the throttle position is set properly (closed < 1%, WOT > 95%).

Confirm the AFR or that the vehicle has sufficient fuel for idling and that the

vehicle is at the normal operating temperature.

Open the Idle Tab and set Idle FB Below rpm to a conservative

3,000RPM and set Idle FB Above rpm to 400RPM. Set both Idle On If TP

Less and Idle Off If TP Over to a conservative 5%.
These settings will activate the idle circuit whenever the engine RPM is below 3,000
RPM and the throttle is below 5%. These settings are not necessarily drivable but
they will allow the vehicle to idle on its own so you can begin tuning.

Start the engine.

Get the vehicle to idle. This may require creative throttle movements to
stabilize the idle until it catches itself.

Confirm that an increase in the Idle% vs Target Table will increase RPM
rises.

If RPM decreases, select the Idle Invert option.

Shut off the engine.
Now that you know how the IAC motor responds, you can start setting up the idle
tables and idle options.

In the Idle Tab, set the option Idle FB Min to -50%
and Idle FB Max to 50%.

Set the options Idle FB Dead Band+ and Idle FB Dead Band- to 0.

Open the Idle Tab and set the entire Idle Target Base table to