OK, i've searched high and low both in posts and over and over on the engine for an answer. i give up and am asking for help.

specs
D16Y8 in a '93 civic
OBD1 harness
stock P28 ECU
manual IM with 2-wire IACV
FITV on TB
new Blox TPS set @ 0.5v closed

symptoms
idle is smooth when FITV is active, but when the engine warms up, the idle begins to surge.
if i unplug the IACV, the idle smooths back out.
i have tested the IACV by putting 12V to it and the solenoid clicks like it is supposed to.
i have checked and rechecked for vacuum leaks, nothing.
the gasket between the IACV and the IM is new, the TB gasket is new, the PCV is new.
i have bled the coolant system extensively with no luck.
throttle cable is adjusted correctly.

EDIT: i finally figured it out last night. i narrowed it down to a vacuum leak between the throttle body and the intake manifold. it had a brand new D16Y8 OEM honda gasket there, but i went ahead and got another one. put it on and same problem. tried some liquid gasket sealant along with the new OEM gasket and same problem. took it back off, cleaned the surfaces, and checked to make sure they weren't warped with a straightedge...flat as a 12 year old. so i got out some Felpro make-your-own gasket paper that i had and traced and cut out my own gasket. slapped it on there and she purrs like a kitten.

the gasket paper was a little thicker than the OEM gasket, so i guess that helped out. also, the gasket i traced was from a D16Z6, so it was a little different than the D16Y8. i was using a D16Z6 throttle body, so maybe i should have tried that gasket from honda. oh well, it works now.


Modified by DelSolDon at 6:20 PM 1/26/2008


Modified by DelSolDon at 7:33 PM 1/31/2008

 

i had a problem with this swap before, test if the normal IACV works buy just hooking it up and hanging, and see if it changes, with mine, i just let it hang in the open and blocked it off

 

ok, here's what i tried today:
changed TB and IACV

the IACV i used was a known good one. still though, even if the IACV is unplugged, there is air sucking thru the top port on the TB.

another thing i tried today was that i put my finger over the IACV hole and even my whole hand over the TB inlet and the idle drops a little and smooths out, but the engine should stall out, right?

that leads me to think that there is a vacuum leak somewhere, but i can't find it for the life of me. TB gasket and IM gasket are brand new. i'm about to toss a grenade in this mafukka

 

yeh, when you cover the throttle body, it should stall, maybe there is a major vacuum leak

 

If your hunting for a vac leak, you can't beat a can of brake cleaner. Spray the **** all over the manifold and see if/when/where the engine responds to it. It never fails at the shop.