2000psi

Like the title says...I searched a ton with no help (yes archived too).

Car is a 99 civic Dx Idle is all over the place from 1100-2000RPM
Manual trans Y7 (Rotary IACV)

I checked the valve with 12V power and it opened and closed, I checked the wire harness...all is well but I got a code 14. When I pulled the valve it was open about 2-3 mm.


CLIFF NOTES: Is the IACV (rotary style) supposed to be open a couple mm at rest with no power being applied? Or should it be sealed %100 until it gets the signal to open? When I applied power it opened all the way.

THANKS A TON FOR ANY HELP!!! I gotta go to school tomorrow night so any and all help is appreciated!!!

Redline96LX

I don't know 100%, but mechanically, it seems if it were TOTALLY closed, and the throttle was totally closed, thatd stall the engine. I can get to the Helms book tomorrow, so keep buggin me if youd like and I'll try to lookup what it says.

2000psi

Thanks I didn't think of that....but doesn't the idle screw let in enough air by itself? or is that just to trim it up/down? Like an idiot, I took apart the plastic end of the IACV. The white plastic cap. I don't know if I put it back on at the wrong angle, I did line up the factory paint mark so it should be ok.....does any service manual go into that much detail? like the inside of the IACV? THANKS!!!

2000psi

bumpish

Redline96LX

At least what I saw on my TB, the screw is to the end, and when idling, the TB is totally closed.

2000psi

up up

EE_Chris

If you unplugged a 3-wire IACV, the idle speed may increase - it even says this in the Helms.

3-wire IACV's do not close down like their 2-wire cousin.

When setting the idle speed on a motor that uses the 3-wire IACV - you don't even unplug it like you would a 2-wire IACV.

2000psi

I have the 3 wire (rotary style) and when I unplugged it with the engine running the idle was surging between 1000-2000 every 2 seconds or so....Thats weird because it should either not respond at all, or the idle should increase, but it just surged. please help because the dealer wants $201 for a new IACV. The weird thing is I put everything back together today and went and bombed a local canyon and the car was running better than ever. I pulled over every 10 minutes or so and shut the car off so the ECU would see it as a "trip". The ECU should pick up a malfunction on the 2nd trip but it didn't.
then when I got home the car was idling perfectly, i got out to open the gate and cames back and the CEL was on again!!! this was after an hour of driving and 5 "trips" so I'm thinking the valve is bad and there is no way around it but to bend over for the dealer since it's a dealer only part and independents don't stock it. Thanks

EE_Chris

A 'trip' is different than what you're doing. The engine has to start cold (or have sat for some time), get to operating temp and then cool back down below a threshold. You pulling over on the side of the road and shutting the car isn't accomplishing this (but good try).

If you unplugged the IACV and the idle speed increase above 1100 rpm, then the surge is normal...assuming the engine was hot and TPS indicated closed throttle. This is activating the fuel cut on decel strategy inside the ECU - its something that saves gas and reduces emmisions.

I am unsure of what you could have mis-aligned or messed up when putting the IACV back together - I've not dis-assembled one myself - so maybe that is your problem...now.

Is the car stock? At around 150k mile mark, my IACV froze up on me (bone stock 99 hatch). The first thing I did was to get the car to operating temp and blast it with some crab cleaner - this has fixed it and has lasted for 80k miles now.

Did this just come out of no where or had you done some maintenance and then this started to happen?

2000psi

the car is at 103K miles right now. I recently pulled the TB off to clean it and adjust the throttle stop screw (I now know you are not supposed to touch this) because my throttle plate kept sticking when i would give it gas. I checked the voltage after adjusting the stop screw and it checked out perfectly .44 closed and 4.5 open. So I pulled the IACV off and cleaned it with some electronics cleaner and carb cleaner. while I was in there I pulled off the white plastic end of the IACV because I have a sick curiosity like that, and there is a little lever inside that hits two plastic stops that are part of the end cap.....that lever is directly connected to the actual rotary valve and makes sure it only opens/closes so far. so my only thing to blame (besides myself) is that the stops are now at the wrong angle and the valve can't open or close all the way.....AHHHH I'm gonna try finding a service manual that will show me the angles. THANKS FOR ALL YOUR HELP...i'm trying to fix this because I'm a poor *** college student and that $201 could buy alot of beer!

EE_Chris

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2000psi &raquo;</TD></TR><TR><TD CLASS="quote">adjust the throttle stop screw (I now know you are not supposed to touch this)</TD></TR></TABLE>

Bolded for emphasis. People reading this - do NOT **** with this screw. It is set from the factory. There is another screw that adjusts the idle speed.

So this problem came out of no-where then? Did you pull of the t-body in response to this erratic idle?

The Helms doesn't specifiy anything that can be fixed inside the IACV...or set/reset - so you looked screwed there, if that is the problem.

What does the idle do if you hold your finger over the entry hole to the IACV? Thats really the only way to 'disable' it.

...and what's that saying - curiousity killed the...

2000psi

I only adjusted the throttle stop screw because my throttle plate was sticking closed, this TB came with the Y8 IM I bought form someone, so i don't know if it was set properly when I first got it. I think my problem might be related to my sticking throttle issue...the plate might have bored out the TB from rubbing it, I think what I'm gonna do is buy a new IACV from honda and use it as a reference to adjust the angle on my old one, then if it works, take it back, if it doesn't hey I already have a new one. honda should accept it back as long as it's unopened and was not a special order right? BTW my idle has been sporadically acting up since i put on the Y8 IM about a year ago...so I finally tried to fix it by pulling the TB and investigating then a day later my IACV acts up thats how this all got started

Thanks dude

2000psi

I got the TPS voltage back to factory specs after adjusting the throttle stop screw so it shouldn't be a problem that I even touched it

EE_Chris

A Y8 manifold - where did that come from? What is the setup? I thought you had a bone stock Y7, as you mention nothing of a Y8 manifold in your opening post. And now you're saying you've always had this problem ever since you installed the manifold...

I don't know about the special order item deal with Honda - call'em for that.

Maness

I've had this same problem for quite some time. I think I'll go back to stock before I ever figure it out.

wedgenix

I've been dicking around w/ my IACV for way too long now....getting pissed and about ready to just go to a damn dealer and say fix it, gimme the bill, and let me get my sanity back. Not sure if a dealer will touch it tho, B18C1 block, JDM ported/polished B16 head, Jackson supercharger, Edelbrock TB, etc. My IACV is a 2 wire deal, and it idles fine cold, then surges all day long when warm. I can stabilize the idle by leaning out the low RPM Apexi V-AFC settings, but then I have a major dead spot in the throttle at ~1500-2200RPM (majorly sux0rz when stuck in my morning rushour metro-suburbia traffic!). Since it idles fine cold (though a tad high for a warm motor), I got the bright idea of bypassing the coolant lines on the IACV....all that did was throw a CEL and *still* do the 1k-2k idle surge thing (with the throttle deadspot, too...even w/ 0 adjustment on the V-AFC at low RPM). Damnit.

I don't have a FITV, so the problem has got to be in the IACV as far as I can tell....I just bought the car a few weekends ago and the prior bonehead owner adjusted the throttle cable to set the idle...it had a 3500RPM Idle. That ummmm "works" but geebus...'nuf said. I guess he thought that was cool w/ the Apexi N1 exhaust screaming while he sat at a red light. When I asked him about the rediculously high idle, he said "Oh, that's for better oil pressure at idle...I study a lot of engine theory" *chough* *bullshit* *cough*. I bought the car anyway since I figured I could fix it and what I paid was less than the aftermarket parts costs that were on it, and it's basically driveable except for 10-20MPH traffic congestion....now it's looking like I'll be paying someone else to fix it. Ah well, at least it'll get fixed....then I'll post what &lt;dealer x&gt; did to get it right, at least in my case...unless anyone has any last-second suggestions. (I'd just buy a IACV myself, but I don't know wtf this fool did beforehand if anything to set the idle properly or what other screws he turned. mibbie I should buy the IACV anyway, slap it in and see what happens....THEN if it's still fux0rd I'll roll it in to a shop. That was as afterthought as I typed this....any comments? Sound like a reasonable plan?)

EE_Chris

If you unplug the IACV (while the motor is fully warmed), what does the idle settle down to? It should settle down to around 500-550 rpm - if its higher than this, lower it down.

Your base idle speed has to be within a certain window for the IACV do it job correctly. When you plug the IACV, it brings the idle up to 'curb' idle speed which is usually 750-800 rpms.

wedgenix

<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 unplug the IACV (while the motor is fully warmed), what does the idle settle down to? It should settle down to around 500-550 rpm - if its higher than this, lower it down.

Your base idle speed has to be within a certain window for the IACV do it job correctly. When you plug the IACV, it brings the idle up to 'curb' idle speed which is usually 750-800 rpms.</TD></TR></TABLE>

Will have to try that once I get home...I guess my prob might be as simple as it just being out of range for the IACV to compensate. Thanks for that basic info, might be exactly what I needed

SOHC_Brian

<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 unplug the IACV (while the motor is fully warmed), what does the idle settle down to? It should settle down to around 500-550 rpm - if its higher than this, lower it down.

Your base idle speed has to be within a certain window for the IACV do it job correctly. When you plug the IACV, it brings the idle up to 'curb' idle speed which is usually 750-800 rpms.</TD></TR></TABLE>

not trying to thread jack bro, but this might be what i'm looking for. I've been going insane, pulling my hair, trying to fix the same problem since last year. Car have been pretty much just sitting in the garage until 2 weeks ago, i got a iacv that i know was working and I have been riding fine on it until yesterday when i went and tightened up my throttle cable opening the throttle a bit. I drove around, parked it, and when i got back into the car the CEL for the iacv came on and the same surging idle between 1500-2000 rpm. I never thought about the higher rpm (900) during idle affecting the iacv or it could be a coincidence. *Cross my fingers* hope thats the problem though. After the incident yesterday, i felt like forfeiting and selling the damn car or getting a swap. I spent like 3 hours this morning looking up used cars and then motor prices and then finally searched for iacv problems and got to this thread

wilsel

I'm having the same problem (only when engine is warm). Lets us know what you find out. I've tried pretty much everything but replacing the IM gasket, and replacing the PCV valve (someone said that could cause it).

SOHC_Brian

i replaced the im gasket, throttle body gasket, pcv valve, oil change, radiator fluid flush, and working iacv all 2 weeks ago. i just undid the tight throttle cable and i'm waiting for car to idle until its warm and then i'm gonna unplug the iacv plug and adjust the idle rpm to about 500 rpm by adjusting the idle screw on the throttle body. Then i'll drive it around again. But won't really know if its fixed or not unless i drive for couple more weeks since i did go 2 weeks without any problem. will keep u guys updated if that **** pops back up.

EE_Chris

Make sure you adjust the correct idle screw. The throttle plate stop screw isn't it.

SOHC_Brian

got it, i should of adjusted the idle screw in the first place and not screw around with the damn throttle cable

wilsel

Forgot to mention I did buy a new IACV, and it still does the same thing (only when warm). I'm about ready to blow this engine, and start over with a B-series.

I tried adjusting my idle, but with the screw all the way turned to the right it still idles at 900 RPM. Turn it to the left, RPM goes up.

2000psi

The thing that's throwing me off is that when I unplug the IACV (car warmed up) the idle surges up and down every 2 seconds or so....with the 3 wire, when you unplug it it's supposed to either not respond, or the idle is supposed to climb and level out, not surge. I don't have any fuel or air intake mods that would cause this problem. I went to Honda yesterday and bought a new IACV and went out to my car and drew the correct angle for that plastic endplate (mine was off!) then took it back in and returned it.
Turns out the valve is cracked open on the new valve too just like my old valve. So I went home and adjusted my old valve to how it's supposed to be, then tried plugging it in w/o it being attached to the IM and the valve closed up like it's supposed to. So I went for a drive (reset ECU first) and the idle was now surging from 2K to 3K at every stoplight, other than that it drove great. It's now surging exactly like a vacuum leak will make the idle surge....I dunno what the **** is going on, anyways I have finals this week so I gotta focus on that, the car will have to wait till this weekend so I can put some time into it.
The only thing I can think of trying now is setting my base idle to ~600RPM and seeing if the IACV can deal with that. Ever since I switched to the Y8 manifold my idle has been high (around 800-900RPM but very stable) so i'm thinking that if I lower the base idle the IACV will be happy and be able to control idle once again (that is if the valve is not broken). TOO MANY VARIABLES!!!!!


Modified by 2000psi at 12:59 PM 6/2/2005