Occasionally I run into a strange issue when I switch to IAS mode during climb phase. Typically, I am not trimmed our right and I am above or below optimal climb speed (170 knots). So my regular practice is to select the NAV capture, Alt Capture and the IAS buttons on the FCC then adjust the pitch wheel to 170. The flight director fires up and shows an adjustment to capture this speed. At that time I will turn on the AP and the aircraft will make small adjustments to capture. However, if I have my climb set up right to begin with, trimmed out at ~170 when I initialize the IAS mode on the FCC, 170 is already showing as the set speed in the EADI. So I click on the AP and FD goes to the roof and the plane pitches to a stall. What is going on here, is this a bug or am I doing something wrong?

I had to double check. The AP IAS set speed doesn't follow your indicated airspeed if only HDG is engaged (at least on my installation). I have to manually set the IAS before engaging otherwise it will pitch up to slow down to the much lower preset. My technique is to first use V/S (preset at 1000-1200 fpm) and allow airspeed to increase to 170 then press the IAS mode button. That always seems to work for me.

You mention a much lower preset speed. Is there a default setting? if so, why is it so close to stall speed.