Hi, I just got done swapping in a newer d16z6 (probably from a 96 or newer) into my 1995 civic lx. It starts up and stays running, revs up beautifully but went it comes back down, it bounces between 750 - 1250 rpm but it will eventually level off and sit right around 700 rpm within about 30 seconds. Also, when it first starts up after sitting all night, it idles @ 1500-2000 rpm and will eventually come back down to about 750 rpm after a couple minutes. I was thinking vacuum leak but I went thru everything and it looks good. While I was doing to the swap, i threw in a new clutch, fidanza flywheel added some poly motor mounts. I did have to take some parts off the d15b7 like the injectors and the alternator since they had different plug connections. Also, for the time being i currently have it running off the stock p06 ecu but I was under the impression that this shouldn't be a problem.

what are your theories????

 

Well the p06 is probably your first problem. Second when you said that your car idles high in the mornings thats normal any car idles high for a couple of minutes while it reaches normal temp. Also the jumping idle must be related to you running that p06.

 

i figured that the high idle in the morning was normal. And i figured that the crazy idling was from the p06.