I had been having severe cold start issues. My IACs were maxed out at 310 and I drilled my TB hole to 1/4", still to no avail. After some searching I finally realized what the problem might be -- when I ported my TB I also filled in that area for the IAC and IAT inlets, of course I drilled a hole to allow air into both areas, but it occured to me it might not be big enough.

I took my drill and doubled the hole for the IAC side and fired her up. Sure enough, even when totally cold (and humid, that seems to make it worse) it shot right up to 1000rpm (what I set it at for this temp range) and stayed put. No surging or anything else.

Woo hooo!!!

Just thought I would share this in case anyone was having a similar problem.

 

How big are your IAC holes now? I think I drilled mine 3/16"
on both IAC and PCV ports when I epoxied & ported my TB.
Haven't had cold start issues. Did you notice any reduction
in engine cold surging (if any was there before)?

 

It's slightly larger than 1/4". I added 2* timing at idle to eliminate the cold start surging.

 

what is surging?

 

rpm's hunting at idle is an IAC's inability to stabilize , and spose it could be called surging at idle