so i just swapped in, an obd1 d16z6 engine into my 1996 civic si which means i converted to obd1. everything went well, car fired right up and drove amazing (thanks again for everyones help). now my idle is high around 1900 when cold and 1200-1300rpm when warmed up and sometimes bounces up and down like a vaccume leak. i cant find a vaccume leak. o and i swapped the intakes so i still have the y8 manifold and before the swap my idle was perfect at about 800. is this something to do with the obd1 conversion or is it an actual idle problem i have to diagnose?

 

Is your Iacv hooked up right? Is it clean? I assume you have a FITV too? did you check it?

 

Check your iacv. Any cels?

 

And if you have some brake cleaner let your car run and spray on and around intake mani if your rpms drop you have a vacuum leak

 

What throttle body? Does it have an FITV?

 

^ im with this guy

 

FITV:

Fast Idle Thermo Valve. This valve is on the d16z6 but not on the Y8. It has a plunger device that allows a faster idle to warm up the car until the thermostat opens.

DIY write up

 

I agree if u r using the z6 throttle body this will cause the high idle. U can fix this by getting a longer hose and bypassing the plunger on the bottom of the throttle body or use ur Y8 Throttle body.

 

as said i kept the full y8 manifold on it and TB with it. ok th for all the input

 

Did the Y8 manifold come from a 99-00 Civic with the fuel injection air control system?

 

I would say do this first. I had a IACV CEL pop up, i cleaned it and it wasnt enough for me. I had to get a new one!

 

Or you can just do a simple vacuum leak test like said earlier. It doesn't cost you anything but bout two minutes. Just take a few pliers and squeeze the hoses going from air intake to engine and see if rpms drop. If they do there is your problem.

 

I am currently having the same problem with the same engine in a 93 civic ex except my problem is much worse. When I start the car it revs out at 3 grand sometimes higher after its warm it still is around 1700. I suspect a bad intake manifold gasket but will definitely check the iacv.