EJ7 Owner

So, I've pretty much gotten every other problem with my 97 HX figured out except this one.

The idle is not working right, so according to my Chilton or Haynes maual (cant remember which it was) I did what it said to do to adjust the idle.

It said to let the engine get up to operating temp, disconnect the plug going to the IACV and adjust the base idle.

Well, when I disconnected the plug, there was no change whatsoever.

So, the other morning, I removed the IACV from the intake manifold, had my sun turn the ignition on, and there was no movement or sound from the IACV.

Well, I called the autoparts stores, thinking I had a bad IACV. Had to wit til today to get one as I was busy with work. Picked it up and had my son help me again testing with the ignition, and this one didn't do anything either.

So, I grabbed some wire, stripped the ends, ran a lead from the battery and one to ground, touched power and ground to the two pins and it clicked like it should.

I next tested the plug to the IACV. One wire has 12V going to it (I think it was green w/white stripe) the other had nothing.

So, what's my course of action here as it seems that my old valve may not be bad? I just haven't taken it off yet to test it with the leads.

Thanks in advance for the help.

Former User

Describe the idle problem, and post all CEL codes thrown.

You'll find the Honda service manual instructions for adjusting the idle speed in the FAQs sticky.

EJ7 Owner

Strangely enough when I bought it a few months back, I had cyl 3, 4 and multiple engine misfire codes. I cleaned the TB, EGR valve/chamber (with new gasket) and the IACV that was on the car. Also checked plug gap and made sure the wires were good (they were) reconnected the battery and the CEL light was off. Drove it off and on for a few weeks before going on the road, probably put 150 -200 miles on it at most. Never came back on..

Cold start has been a pain in the *** since I bought it. Have tried adjusting idle according to the manual I referred to earlier (I looked in the sticky thread for idle adjustment, did not see D16Y5) and when I pulled the IACV plug, nothing happend. I mentioned that in my opening post. I didn't adjust the idle set screw because nothing happened when I removed the plug.

At cold start. It idles at around 400-500rpm but will die if you don't keep the foot on the gas pedal.

Once it's warmed up, it stays running on its own at around 400-500rpm

It's a two wire IACV and I'm assuming that one wire is power, the other is ground. If I have 12V to one wire, provided the ground is good, I should get power to the IACV, but nothing is happening. So, it makes me think it's an electrical issue as I put 12V to the IACV from the battery it works. I put 12V to it from the ignition when it's connected to the plug from the factory wiring harness, nothing happens.

Former User

An electrical problem in the IACV circuit generally throws a CEL code.

Just looked. The diagram for your engine is indeed there (manual trans or CVT?). To set the base idle speed, you must hook up an external tach to read engine rpms accurately.

EJ7 Owner

I've looked at the sticky in this forum. Maybe I'm not seeing it.

Give me a hint on exactly which of those sections to look in. Not askin to be spoon fed, just point me in the right direction.

I'd like to get this issue resolved soon as I've got a project to get crackin on after the Civic is running right.

EJ7 Owner

How about this...

Can someone tell me what the two wires to the plug for the IACV are?
I know one wire has 12V when ignition is on. Is the other one a chassis ground?

If that's the case, I see there is another plug below the IACV that is on the same length of wiring going back to the main harness. I'll have to test that one to make sure.

Former User

Section 5i

Only two links are relevant (96-00 Civic idle adjustment). Click both. Do you hit pay dirt?

mk378

One wire is 12 volts whenever the key is on. The other wire is connected to the ECU. The ECU pulls this wire to ground to energize the IACV coil, which opens the valve and increases idle speed.

There are several plugs the same and they can be mis-plugged. You need to check wire colors against the manual to be sure that all the harness plugs are plugged into the proper devices.

EJ7 Owner

I saw this...Adjust 96-00 Civic D16Y8 (Manual Transmission) Idle Speed...But as I don't have a D16Y8, I didn't look.

Then I found this one...Clean the IACV...but that IACV is different than mine, although in principle, it works the same.

So I did find the links you were talking about, just didn't think they applied to me.

Anyway, the cleaning of the IACV is done, now it's just trying to determine if my wiring is jacked up and how I can go about repairing or replacing it.

Former User

So now you have instructions on properly adjusting the idle speed - direct from the service manual for your car. Follow the instructions to the tee, and then report back.

EJ7 Owner

I can't adjust the idle speed til I figure out the issue with the IACV not working, as I've mentioned before.

Let me get that part fixed before I go adjusting idle speed...

Former User

In this thread, I have yet to hear anything indicating that your IACV is not working. Maybe I missed something. Can you briefly summarize?

Also provide detailed car information. Any modifications or is the car completely stock?

EJ7 Owner

Ok, now we're getting somewhere.

If I remember right, one wire is green with a yellow stripe the other is just black. I'll look at it and know for sure once the wife gets home as I'm watching the kids.

I did find this link...

https://honda-tech.com/honda-civic-d...guide-3146770/

But I can't understand much of anything past the pictures of actual plugs. Those diagrams are confusing as EFF...

On the plug going to the IACV, the terminal that would be closest to the release tab is the one that get's 12V with ignition power.

Question. Does that ground HAVE to go to the ECU or could I just splice in a new ground going to the chassis? Don't worry...haven't done it, just curious if it would work in case that is my only option as I really don't have all the tools to rip out a harness and tear it apart to find the problem.

EJ7 Owner

Bottom third of post #1.
Last section of post #3

EJ7 Owner

Other than a cheap *** air intake and filter I put on it because the factory air box was cracked and beat to hell, it's bone stock as far as I know.

And there are no leaks around the coupler between the air intake and throttle body or the hose from the valve cover to the intake pipe. All new clamps for both of those.

Former User

No definitive evidence for an IACV electrical problem in either post.

EJ7 Owner

Ok...

So, the green wire is 11.4-11.7 volts with ignition on.
The black wire is definitely ground.

I tested as follow.


Removed plug from IACV.
Using my volt meter, I put the positive lead to the green wire's terminal and the negative lead to chassis ground. 11.5ish volts.

Then put the positive lead to the green wire's terminal and the negative lead to the black wire's terminal. 11.5ish volts.

Removed the IACV from the intake, put the plug back on, turned on ignition, nothing happened.

I then used two wires to bench test the IACV. Ran one wire to chassis ground and one to the positive terminal of the battery. Touched the wires to the respective pins on the IACV and it opened. Removed the wires from pins, IACV closes.


So...if I'm getting voltage from the green and the black wire is good for ground, why the hell is that damn IACV not working???

I am thoroughly confused.

Former User

^Post this information.

FYI - The two wires in the IACV connector should be Yel/Blk and Blk/Blu.

Sounds like you may be testing the power steering pressure switch connector.

EJ7 Owner

Red 1998 Honda Civic HX D16Y5, manual, FWD, sun roof, A/C power windows/locks.


It's green and black. Trust me on this.

I wonder if the plugs somehow got switched. Are the plugs the same shape for the power steering switch/IACV? I've not removed any plugs from any of the engine except the IACV plug.

Former User

Read my last post. Trust me. You are not working with the IACV connector.

EJ7 Owner

How much money are you willing to lose? I know what an IACV is and where it's located. I also know what a power steering pump is. I'm not stupid. I am also not color blind. So instead of assuming I don't know what I'm talking about, how about you help me find out what the hell is going on.

Former User

Be prepared to Paypal me a lot of money.

And settle down and try to learn something. Otherwise, this thread gets locked.

EJ7 Owner

In my hand. IACV. Plug that I have been testing that is the only plug I've pulled off the entire car. Green and Black wire.

Former User

Please carefully read all posts in your thread.

mk378

You may not have plugged it wrong, but apparently someone before you did. Look at all the 2 wire plugs and see if there is one with yellow-black and black-blue wires.

The other kind of remote possibility is that someone repaired the harness by splicing on a different plug from a parts car. There would be evidence of that if you look for splices a few inches away from the plug.