Hello all!!

I just took my IAC off my 2000 civic EX manual swap to clean it. I actually disassembled the unit not knowing it wasn’t necessary to do. I put it all back together and now my idle is at 3500 RPM.

What went wrong??

 

Remove air intake system.
Use your finger to cover hole inside throttle body leading to IACV while engine is high idling.
Does idle speed drop to normal or below?

 

It stalls if I cover it. It’s sucking some serious air through there.

 

Are any CEL codes thrown?

 

Secondary o2 sensor (doesn’t have one) and a couple codes regarding the also missing automatic transmission. Whoever swapped it left the auto ECM in the car

 

In longterm, you need to purchase a 99-00 Civic P2P ECU for a manual transmission and replace the 3-wire IACV with a 2-wire IACV.

In the short term, remove your IACV and check whether the spring-operated IACV window that controls air bypass to the IM is seized in the fully open position.

 

Will a two wire IAC fit on the same intake? I’m relatively new to the Honda thing, but I thought that automatic trans and manual trans cars have different intake manifolds?

 

I'm pretty sure that you can install the 2-wire IACV on the automatic Y8 throttle body without installing a manual Y8 IM.

 

Awesome, thank you! You’ve been a big help!

 

The intake manifold is not machined for the IACV... one would have to drill the inlet and outlet holes as well as the two bolt holes that would hold the IACV to the intake manifold (and thread them obviously) in the appropriate place.

 

Question. Why specifically the P2P ecu?

 

The OBD2B P2P ECU is specifically designed to run the stock D16Y8 engine in your 99-00 Civic.

 

What about the converse? Will the 2-wire manual Y8 IACV fit on the automatic Y8 throttle body?

 

No sir, it will not. I have never tried to convert a 3-wire IACV car to a two-wire IACV and keep the auto T/B... so I am unsure if you could simply unplug the 3-wire IACV on the auto T/B, convert the wiring to the two wire style plug and connect the conventional IACV to the back of the intake manifold and the engine idle properly. I have always switched to a manual T/B.

Just to be clear: The 3-wire IACV found on auto EX and all DX/LX Civic models mounts to the bottom of the T/B. The 2-wire IACV found on the manual EX Civic is mounted to the back of the intake manifold and NOT on the T/B itself like the 3-wire IACV.

 

I defer to your vast engine swap knowledge.

Is there any theoretical reason for thinking that this^ would not work?

FYI
OP has auto Y8 ECU, IM, TB, and IACV but has a manual transmission swap.

So, could OP possibly fix his longterm issues by buying a manual 99-00 Civic P2P ECU and doing the 3-wire to 2-wire IACV trick?

 

Can you tell me a part number for the correct manual transmission throttle body?

 

A guy I work with is basically a Honda guru, he’s built his civic several times over. Multiple setups and engines. He said I should just go get a manual ecu and try and find a manual trans engine wiring harness. He believes that would be the simplest and easiest solution. Use a two wire IACV and and the rest should be plug and play.

What are your all’s opinion on this?

 

The throttle body part number is: 16400-P2M-Q01
The IACV part number is: 36450-P2J-J01

If I were doing this, I would find a complete '99-00 Civic EX manual intake manifold and install it on the engine. Then convert the light grey 3-wire oval IACV plug to a dark grey round 2-wire IACV plug on your current engine harness. You will not use the orange wire... just the blue/black and the yellow/black wire. You will then move the blue/black wire from slot 6 to slot 23 on the ECU "B" plug. Lastly, plug in your manual P2P ECU and you should be Good to go.

If you cannot find a complete manual intake manifold, you could modify the auto I/M and install a manual T/B. You will still need to make the wiring changes to your current engine harness and replace your auto ECU with a manual P2P ECU.

 

If the 3-wire IACV is closed at rest, then I see no problem why it wouldn't work. However, if it is open at rest, it will create a hella vacuum leak and idle really high... and maybe even hunt up and down.

 

The service manual information below indicates that the 3-wire IACV is open at rest (unplugged), whereas the 2-wire IACV is closed at rest (unplugged). Therefore, even after a 3-wire to 2-wire conversion, the 3-wire IACV would not work properly with the manual P2P ECU, as you stated earlier.

 

[QUOTE=muellersfan;52293741]In longterm, you need to purchase a 99-00 Civic P2P ECU for a manual transmission and replace the 3-wire IACV with a 2-wire IACV.

Ok so I switched to a skunk2 pro series intake manifold. And the old style plug was flat and 3 pin. The new style is a round two wire. So what do you with that 3rd wire on the original plug.

 

[QUOTE=ThatSlowEKSedan;52848152]The orange/black wire is cut and taped back (no connection) and then you have to move the black/blue wire at the ECU to the appropriate position (auto to manual conversion).

 

[QUOTE=JRCivic1;52848555]ok so even though my car is 5 speed from factory I still need to switch the ecu?

 

[QUOTE=ThatSlowEKSedan;52848559]What engine do you have ?

 

[QUOTE=JRCivic1;52848564]D16y7