That is the issue because the car is trying to lower the idle down, while you are bumping it up.
Do you have a reason for wanting a higher idle?
Basically thre idle set procedure is to unplug the IAC, adjust the throttle stop screw to desired engine RPM and then reset the cmputer and plug in the IAC. The IAC can raise the idle up (cold start, imminent stall, engine load) but can't lower it due to the throttle stop screw holding the plate open.
You can bump the idle up with the throttle screw, but if the idle is over 725RPM the computer will always trip the Code 13 as it's trying to lower the idle.
You may also come across a TPS code if the idle voltage is out of the 0.6V-1.1V initialization range.