recently swapped 91b18a w/ man 5sp into a 90 da that had blown b18a and auto trans. after the engine and trans were installed i developed the surging idle trouble. i didnt have this trouble with this engine when it was in the other car so i am guessing it has something to do with the year differences or the auto to manual trans swap. i didnt change the manifolds are they different other than one vacuum port position? i tried to swap the iacv and the map with the 2 vacuum selenoids also made sure the coolant is full and there is no air in the system. i checked the trhottle cable for proper adjustment and have tried adjusting the min air rate screw no luck its idles great until warm then surges. i also have tried pinching off vacuum line to check for external leaks. also the 90 has a black box on passenger side firewall with 3 vacuum line running to it that the 91 doesnt have
i also tried switching computers . i searched this topic and didnt find help on my specific trouble any and all input is greatly appreciated

 

well first off those vac lines need to be plugged, this could be your problem, any leak however small can cause big things to happen on the BAD side....i had the same problem, my injectors had bad and cracked seals so i got new ones and it fixed my problem not sure if thats yours check em anyway