2lude4u

Ok, I swapped an H23A into my EF hatch using Hasport mounts in the spring & ever since have have a high idle that I can't get to drop down, along with fix some start-up issues. I'll first describe the set-up since any of these factors could be an issue.

Euro wagon H23A block
Well ported H22 head with Crower 3 cams
Blacktrax Stage 3 manifold
STR 68mm throttle (I think this is the problem)
No IACV or FITV
Hytech header
Custom 2 1/2" exhaust with only 4-15° bends
MSD ignition
Tuned with an AEM EMS
M2A4 trans w/ a Quaife & carbon synchros

Compression & Leakdown are both good

It does not seem to have any vacuum leaks

Ignition at
1000 rpms- 23
1300 rpms- 28
1600 rpms- 33
2000 rpms- 37

AFR at warm up is 14.7 (I need to richen that up a little). AFR after the car is warm is around 14 (& lean this out).


So here's the problem-

If I coldstart the car without applying some gas it will briefly start (1/2 sec.) then die, so I have to give it some gas (hold it at around 2000 rpms) for 1-2 minutes for it to warm up. Then it will find itself resting at 1750-1900 rpms at idle throughout the rest of the time that I drive it. If I let off of the gas after say only 30 seconds of warm-up the idle will drop to around 1000 rpms, seem to struggle a little for 2-6 seconds, choke then die.

During warm starts, I don't always have to apply gas. It will start up, almost die, catch itself then go up to 1750-1900 rpms. Oh, on colder days the idle seems to be a little higher than warmer days.

Since this T-body does not have an idle adjustment screw. I have adjusted the throttle plate on the T-body to be closed as much as it can be in an effort to reduce the idle rpm's. I don't think any air is getting past the plate at idle. It's all going through the hole in front of the plate. If I use my finger to block that hole it dies of course. I have to cover almost 2/3 of the hole with my finger for my idle RPM's to drop to what seems right.

Today I through a boost/vacuum gauge on it to see if the vacuum readings can clue me in to anything. Vacuum at idle was between 16-17 Hgin (or whatever the measurement is), vacuum during cruising was 12-15, & vacuum during no throttle, ie engine braking was around 19. These vacuum #'s from what I know seem low, as in there should be a little more vacuum to be "normal".


The possible issues as I see it:
1. The STR T-body just plain lets too much air through it
2. The RPM readings are not accurate for this swap. Maybe 2000 rpms on the tach isn't 2000 RPM's. The engine speed does seem to be idling faster than it should be, but 1000 rpm seems to sound slower than it should maybe? The swap uses the original cable VSS of the hatch.
3. You tell me

Thanks for reading my long thread & any help you may provide.

mgags7

i originally had problems getting my str 70mm tb to idle right

firstly, i bet you have tried this, but there is a hex idle adjustment on the back....

what i ended up doing: make the hole that goes through to the IACV in the gasket smaller, i remade that shitty paper gasket outta real gasket paper, ported the opening myself, then cut my own gasket.....and then i screwed down the idle screw all the way....

these throttle bodies have a little cutout in the side of the butterfly so they can run the car without an IACV, that is whats letting in the extra air, so cut down the IACV and it should be good....

Hawkze_2.3

Does the idle go down if you push on the rotor on the TB to close the butterfly? Maybe the TB doesn't seal well or isn't adjusted right???.....

Attaus

You might get it to lower a little bit but the car will always be hard to coldstart with stage 3's.

2lude4u

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hawkze_2.3 &raquo;</TD></TR><TR><TD CLASS="quote">Does the idle go down if you push on the rotor on the TB to close the butterfly? Maybe the TB doesn't seal well or isn't adjusted right???.....</TD></TR></TABLE>

The throttle body plate can't close anymore than it currently does, it is CLOSED.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bb4ever &raquo;</TD></TR><TR><TD CLASS="quote">
firstly, i bet you have tried this, but there is a hex idle adjustment on the back....
</TD></TR></TABLE>

Where is that?
I've seriously looked everywhere on the T-body for idle adjustment methods. I've searched & it seems that the only way of adjusting idle with the STR T-body is by adjusting the throttle plate position which is done by using a hex wrench under the rotor which I have done & closed the plate all the way.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Attaus &raquo;</TD></TR><TR><TD CLASS="quote">You might get it to lower a little bit but the car will always be hard to coldstart with stage 3's.</TD></TR></TABLE>

I've had Stage 3's in my H22 Prelude & it didn't have any start-up issues. My start-up issues may be unrelated to the high idle, just a tune that still needs to be worked out, but I figured I'd mention them in case it is related.

Hawkze_2.3

Hmmmm...intake manifold gaskets are all good?

2lude4u

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bb4ever &raquo;</TD></TR><TR><TD CLASS="quote">

what i ended up doing: make the hole that goes through to the IACV in the gasket smaller, i remade that shitty paper gasket outta real gasket paper, ported the opening myself, then cut my own gasket.....and then i screwed down the idle screw all the way....

these throttle bodies have a little cutout in the side of the butterfly so they can run the car without an IACV, that is whats letting in the extra air, so cut down the IACV and it should be good.... </TD></TR></TABLE>

So are you saying you basically used a modified/custom gasket to effectively reduce the size of the hole that is in front the the throttle plate?


The intake mani-gasket is tight, I double-checked. It's the "insulating" type (hondata) that usually needs to be tightened a couple times anyways after initially using it. The gaskets for the IAB plates don't seem to have any vaccum leaks (I've felt around them during idle).

mgags7

Yes i cut my own gasket outta gasket paper and made a pretty small hole for the iacv, its the only hole in it at all

the adjustment is a 4 or 5mm hex key, and its countersunk on the back side, above the tps

wait why no iacv?? if you dont have one then just make a gasket with no hole in it at all

2lude4u

I have an IACV bolted in place, but I don't use it (don't want the coolant lines warming the manifold up). I haven't had an IACV hooked up on any of my Honda's for years with no problems. I'll reduce or block the hole for the IACV & see if it helps. It's more than likely the issue because it seems to be pulling a lot of air.

tacticalcustoms

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2lude4u &raquo;</TD></TR><TR><TD CLASS="quote">I have an IACV bolted in place, but I don't use it (don't want the coolant lines warming the manifold up). I haven't had an IACV hooked up on any of my Honda's for years with no problems. I'll reduce or block the hole for the IACV & see if it helps. It's more than likely the issue because it seems to be pulling a lot of air.</TD></TR></TABLE>

Do you want me to bring Phou Kong up? hehehe j.k sounds like your are still having problems man. If you need any help you should hit me up. I'm down to come check it out

mgags7

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2lude4u &raquo;</TD></TR><TR><TD CLASS="quote">I have an IACV bolted in place, but I don't use it (don't want the coolant lines warming the manifold up). I haven't had an IACV hooked up on any of my Honda's for years with no problems. I'll reduce or block the hole for the IACV & see if it helps. It's more than likely the issue because it seems to be pulling a lot of air.</TD></TR></TABLE>

the coolant lines on the IACV are just so it doesn't freeze in very cold temps, you can just disconnect them, if you look, all they do is go in and circluate in an empty chamber inside that little metal plate....so take those off then just let the IACV function normally

2lude4u

Ok I reduced the size of the whole it has helped drop the idle back down. It has also improved start-up, both cold & warm.

I haven't been able to totally work it out yet because I realized the STR T-body creates a vacuum leak (poor design) by not completely covering up the oblong hole on the manifold itself for the IACV. In the past I've been lucky to get it to seal up with some Honda-bond, but not this time around.

mgags7

true, the prelude intake manifold sucks for this tb.....when i portmatched an extra h23 plenum to my 70mm str, i was left with less than 1/8" of metal between the iacv port and the main hole....

also, it leaves that opening on the bottom, that used to be for the FITV, open, and it makes my intake whistle like a damn turbo when the air rushes over it, pretty annoying

2lude.....consider using that thick pepboys gasket paper thats supposed to be for water seals etc, its like 1/8" thick and grey

but i'm glad that making the hole smaller helped....good luck man

alterdcreations

i am dealing with that right now
i overbored into the cavity below and the iacv opening.
alot of machine and welding and plating but when there done it should be worth it.
i feel that you have to weld iacv opening and then match bore to the throttle body size. if you thing 70 is big try a 74mm

alterdcreations

i was told by rs machine to just use a type r gasket and match it to fit.
my upper intake is still at the machine shop so i havent tried yet

alterdcreations

i went to the shop and picked it up. all i had them do is match port the opening about 1 1/2 inches in and i will finish it my self along with the rest of the manifold

here is the opening



here is the throttle body mounted