SprayinCX

first of all i have a 96 civic dx. i just got swapping a y8 manifold onto my stock dx engine. i am using the stock Manuel dx ecu. i am also using the stock dx throttle body. that way i can keep my 3 wire iacv. now for the question.

my idle keeps jumping up and down from like 1.5k to 3k. i have done the following:

checked for vacuum leak
checked all connections
made sure that the iacv connector is reading the right voltages/ ohms
reset ecu

the only thing that i haven't done that i can think of is clean the iacv. my question is, how do you clean a 3wire iacv?

SprayinCX

so does anyone know how to clean a 3 wire fast idle valve?

Daedus

That is a common problem associated with the y8 IM swap. Aside from the obvious vacuum line problems, check to see if your IM is bolted down tightly and that the new gasket is in good condition. To me, what you're describing has to be vacuum related somewhere.

If it goes away when fully warmed up, it's just a symptom of the IAT sensor being bypassed.

No idea on 3 wire fast idle valve

Lord Helmet

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SprayinCX &raquo;</TD></TR><TR><TD CLASS="quote">so does anyone know how to clean a 3 wire fast idle valve?</TD></TR></TABLE>

use brake cleaner on the screen, comes right off with no residue at all.

SprayinCX

well i cleaned the iacv on the bottom of the TB. i retighted all the manifold bolts. i have rechecked all hoses and stuff. any more ideas.

does it matter that i am running the stock dx ecu. that is the motor i have.

maybe i should go ahead and put the y8 head on there as well. but i don't have a ecu to run it yet.

EE_Chris

Did you swap on a 99-00 Y8 manifold that has the air injection holes just above each intake runner and you forget to seal them off?

SprayinCX

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EE_Chris &raquo;</TD></TR><TR><TD CLASS="quote">Did you swap on a 99-00 Y8 manifold that has the air injection holes just above each intake runner and you forget to seal them off?</TD></TR></TABLE>

i did have on of those on there and i did seal them off. then i changed it a 96-98 one and it still does it.

EE_Chris

If you cover up the hole leading to the IACV, what happens - don't bother unplugging it - it doesn't close down like the 2-wire types.

SprayinCX

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EE_Chris &raquo;</TD></TR><TR><TD CLASS="quote">If you cover up the hole leading to the IACV, what happens - don't bother unplugging it - it doesn't close down like the 2-wire types.</TD></TR></TABLE>

don't follow. what do you mean leading to the iacv? closing down?

jaycapz

This may sound REALLY DUMB! But, if you have a bad PCV valve on start up you get a rapid 1-3 second continous rev on startup, from 1-3K ... looping. Thats if the valve is stuck open that is.

Im dealing with a possible IACV problem myself, wish I had more info to offer!

Good luck.

EE_Chris

When extra air is introduced into the manifold, engine rpm increases.

Extra air has to bypass the throttle plate somehow but it has to be regulated (IACV job).

So, the IACV has an air passage that leads to it BEFORE the throttle plate (and then an exit AFTER the throttle plate) - its this hole that I'm asking you to cover.

When the idle surges, its typically due to the fuel-cut strategy that the Honda ECU uses (along with many other manufacturers). When engine rpm is above 1100rpm and the TPS shows &lt;.5v, the ECU cuts off the injectors (kind of like when going down a hill and you let off the throttle - helps save some gas).

So basically:

1100rpm + TPS &lt;.5v = fuel injectors off

So you're at a light idling, as engine speed increases above 1100rpm (from any unmetered source of air a.k.a. vacuum leak) and the ECU sees the TPS is &lt;.5v, it cuts off the injectors (notice I make no mention of vehicle speed - this strategy is independent of that parameter). As engine speed falls below 1100rpm, the ECU cuts the injectors back on but with a vacuum leak, engine speed immediately begins to rise again - and so the cycle repeats itself.

Now, with a 3-wire IACV, you can't simply unplug it like its 2-wire cousin - they operate and are constructed in a totally different configuration. With a 2-wire, you could unplug it, and it closes down thus sealing off that air passage. With a 3-wire, if you unplugged it, it could very well open up a bit more and increase engine speed - so again, cover up this hole. You'll probably throw an IACV code, but just reset the ECU to clear it.