Ok, I just had a b18c1 USDM engine with about 115k swapped into my car. Its a 96 obd2 and is running a p72 obd2 ecu. There are no check engine lights.

Heres the problem:

I start the car and it idles at around 1500 for a little bit, then when I press the throttle itll drop all the way down to 100 rpms and it'll start fluctuating and almost die. When I step on the throttle and go up to 3k it drops all the way down and dies. Then when I start it up, does the 100 rpm idle thing, and can not hold a smooth idle at all. It's really frustrating.

What I've done so far:
Clean the IACV put it back (didnt help)
Replaced the IACV with one that was working (didnt help)
The spark plugs and wires are fine, I took them from my old swap that was running fine. Dizzy was working fine on the old swap just a week ago.

I really dont know where to go from there! It has no ecu codes, and the one time I drove it it ran ok, but once I came to an idle, it dies!

 

idler screw? fuel pressure? dirty injectors not spraying fuel properly? just trying to throw ideas out there also you mentioned spark plugs and wires are fine did you double check each one is getting good spark even though it was good on your prior swap

 

I had the same problem a while back when I did my swap. It turned out to be my dizzy

 

sounds like tps and map plugs are switched !

 

Is the ignition timing correct?