more fun with the "mini-me"

well, I got the civic running, it ran great... until I was coming home from work and now it won't idle, as long as I keep the rpms up it runs great, but if it gets under 1200 or so, it just shuts off. my first guess is the IAC, but like i said in my earlier post, I know squat about hondas, so I wanted to ask advice... reminder the car is a 90 with a d15 block from a 95 and a d16 head from a 96. I don't think that either is Vtech-at least I don't see anything resembling a metal thimble on the distributor or any solenoids of the injectors... the block was originally turbo, but all that is left is the tube coming out of the pan. thanks in advance for any advice...