Don't know about on thr rst, but some iscv control the full range of idle right down to zero.
If it were mine I would check the co when hot is ok, then junk the iscv and add ifnecessary a stop on the throttle linkage somewhere to set a idle speed = end of worries, if mapped nicely/correctly after a few seconds will idle on it's own from stone cold.
Mapped a saxo friday no iscv on that one, idles from stone cold 100% perfectly, aftermarket ecu emerlad K3.
My cossie idles perfect from cold, at 950 unless I want a faster idle such as when warming car in winter then switch to different warm up map(switch) idle cold is either 1500rpm or on other 3rd map 1900rpm
tabetha