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Mounting the OBD-1 IACV. Those of you converting your 96+ cars to OBD-1 for tuning purposes are going to run into a problem with the Idle air control valve. Basically the IACV controls how much air bypasses the Throttle body to maintain a smooth idle. The OBD-1 IACV is a 2 wire linear type, and is not compatable with the 3 wire OBD-2 rotary versions. You can either run an entire OBD-1 Intake and TB, or modify your existing one like I did if you were not lucky to get one with a 2 wire. This is not for the faint, you will need to drill, tap, and grind on your parts.

First make sure your intake has the boss's cast into it. The throttle body is designed to work with both versions, so the only mod needed is to the intake manifold itself. You will need a IACV from a VTEC OBD-1 engine. One bolt hole is already drilled and tapped, so you can bolt your IACV up by the one and use it as a guide to drill the other hole. Then tap this hole( I used 5/16-18 tap and bolt). Do not drill/tap too deep, or you may create a leak, about 1/2" deep is plenty. The throttle body has 2 bypass holes in it, you'll be able to see this square shaped pattern on the upper left of the intake where the TB mounts, and you want to drill here so that this hole meets with the first hole of the new IACV. Basically you want to connect this passage with the closer one in the IACV, but DO NOT drill thru into the intake tract. The other hole further from the TB get's drilled thru into the intake tract. Hope pics explain better. You will then need to make a block off plate for the bottom of the TB where the old IACV was removed. I used a small scrap of carbon fiber(it's all I had, really) and used the 3 wire IACV as a template to drill the holes. I also had to grind into the manifold casting to clear the plug for the IACV. Then you are ready for install.

Mods feel free to add arrows to my pics or edit as necessary, I'm not that good at explaining how to and don't know how to edit photos.
 

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Discussion Starter #5
possibly, however I've heard so much conflicting info and my car is already apart geting turbo'd, so I needed a quick solution.
 

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i have heard so much mixed info about this as well. i did the conversion myself, and it didnt help, and ended up putting my y7 tb, back on my z6 mani, and i blocked off the stock iacv on the back of the z6. still dont know how it works yet because my car's not done.

i also heard you can still use your 3-wire, then just unpin A13 on the ECU and ground it. i cant remember if you still needed to move A14 to A12 tho. but you DO need to if you actually do the conversion.

i need to stop tallking before i confuse myself and others.

matt
 

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Discussion Starter #8
Yes I understand it's NOT NEEDED if you are just updating your intake to a Y8/Z6 style, but when you are converting to OBD-1 so you can run a chipped ECU you have to run a OBD-1 IACV. I researched it extensively before I did my mods the ECU will not recognize the signal from the wrong IACV and bad idle will result. Unless I actually test what is happening with the ECU and IACV(what kind of signal it is) and compare OBD-1 and OBD-2 it won't be known for sure.
 

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I did this conversion when I did the auto to manual swap on my 96 ex and the damn thing still surges when its like 20 deg or colder out......
 

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Discussion Starter #10
If it surges the ecu may need to be reset, or it simply doesn't have enough "range" in it's idle adjustment and surges. Try reseting your ECU when it's 20degree's or colder and see what happens.
 

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allwheeldriveturboboxer
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as mentioned, you should have just bought a manual y8 mani; to pay for that, you could can easily sell auto y8 manis to people w/ y7's who want to upgrade from their downdraft setup.

i guess you would have to obtain a 'normal' side-draft TB instead of the y7 one...no wait,...you could do the block off you did to the 7 tb and not have to cut into any manis hehe

omg what a hassle dude! lol
 

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rkcarguySI said:
If it surges the ecu may need to be reset, or it simply doesn't have enough "range" in it's idle adjustment and surges. Try reseting your ECU when it's 20degree's or colder and see what happens.
its weird because my batt terminal came off at my gf's house in like 20 deg weather, and then it started surging, b4 it didnt..... I dont know why it does now all of a sudden....
 
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you don't have to run a 0bd1 Iac the only 96-00 that are 3 wire are the y7 motors the ex y8 have a 2 wire Iac, so u do not have to use a obd1 mani,, just use a 96+ ex the manual ones have the IAC on the manifold , if u get a auto mani it has the IAC on the TB, plus they flow better than the z6 mani's
 

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Discussion Starter #15
Mine wasn't a Y8 auto it's a Y7 manual that had that stupid vertical TB. The Y8 auto unit was sitting here in my shop off of a bad engine it was a freebie, so i decided to make it work.
 

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i am running (or will be running) a chipped P06 (also OBD1.) in my 96 dx. before when i converted to the 2 wire it did not help. i will be finding out for sure what works pretty soon. i just need my dp flange to block off the wastegate hole so i can start it up.

matt
 

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allwheeldriveturboboxer
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96_civ said:
i will be finding out for sure what works pretty soon.
what do you mean? what specifically are you curious will 'work' or not?

you mentioned you had an obd1 ecu to your 96 dx and the 2-wire iacv 'did not help'...what does that mean? did you perform the famed pin swap on the cabin harness for the 3-wire to 2-wire iacv issue?
 

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allwheeldriveturboboxer
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96_civ said:
yes, i moved pin A14 to A12 and grounded A13.


you don't have to ground a13; it's an extra wire from the 3-wire iacv that will just be chilling in your engine bay. I used it as the vtec wire from the ecu to the solenoid since my cx harness didn't have the wire and it was one less wire i had to run into the bay.

i have a '97 cx. i put in a y8 years ago, installed a jumper harness, did the pin swap above and the 2-wire iacv that was on the back of the manifold( which was previously a block-off because in 98 i put the y8 mani on my built y7) worked just fine.
 

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Discussion Starter #20
96 Civ it sounds like you and I are doing the same thing to the same car, mines a 96DX as well. Alot of people dump on it but I think it's a good engine to start with, the P2E, P2A, and P2F engine codes have the beefiest stock pistons for turbo use. Keep in touch on your progress, I'm about done with kit mechanically about ready to tackle the wiring.
 
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