IACV valve?

[cp[mike]]

this motor has always idled strangely, even when steve had it. idle is controlled solely by the IACV, theres no idle adjustment screw, no FIV, etc. it has a USDM IACV from an OBD1 prelude, with an adaptor plate.

ive been having issues with my car, and they are getting worse, and im pretty sure its because of the IACV.


symptoms (in order of appearance):

- idle has ALWAYS erratically varied by +/- 50rpm.
- car sometimes stalls when going into neutral, car warmed up, with AC on
- car randomly hiccups while cruising at a steady speed
- if sitting idling after fully warmed up (after driving), itll stall after 1-2 minutes
- after stalling from sitting idling, the IACV audibly buzzes.


questions:

- does the IACV adjust air intake while at cruising speeds?
- has anybody ever heard an IACV buzzing before?


hypothesis:

- all of my random, hard to diagnose issues seem to be somehow related to the IACV. after stalling (with the ignition still on) the IACV buzzes. if i turn the car off, start it for a couple seconds and then turn it off (ignition on), the IACV does NOT buzz anymore. does the IACV use an electromagnet to adjust the plunger?


im pretty sure its the culprit, id just like external insight before i go replacing it.

[MRX]

i'm pretty sure the hiccup at cruising speed is due to something else be it ignition, fuel, or ecu related.

Can't say much about the buzzing tho...strange

[cp[mike]]

ive been having separate fuel or ignition related issues as well. i have an MSD 6AL and ill be getting a walbro pump and a new FPR, but thats besides the point.

im pretty sure my IACV is taking a shit on me, and its getting very annoying to deal with, with the car randomly stalling at lights...

[owequitit]

this motor has always idled strangely, even when steve had it. idle is controlled solely by the IACV, theres no idle adjustment screw, no FIV, etc. it has a USDM IACV from an OBD1 prelude, with an adaptor plate.

ive been having issues with my car, and they are getting worse, and im pretty sure its because of the IACV.


symptoms (in order of appearance):

- idle has ALWAYS erratically varied by +/- 50rpm.
- car sometimes stalls when going into neutral, car warmed up, with AC on
- car randomly hiccups while cruising at a steady speed
- if sitting idling after fully warmed up (after driving), itll stall after 1-2 minutes
- after stalling from sitting idling, the IACV audibly buzzes.


questions:

- does the IACV adjust air intake while at cruising speeds?
- has anybody ever heard an IACV buzzing before?


hypothesis:

- all of my random, hard to diagnose issues seem to be somehow related to the IACV. after stalling (with the ignition still on) the IACV buzzes. if i turn the car off, start it for a couple seconds and then turn it off (ignition on), the IACV does NOT buzz anymore. does the IACV use an electromagnet to adjust the plunger?


im pretty sure its the culprit, id just like external insight before i go replacing it.

As far as I know according to the manuals, the IACV seeks to maintain an idle speed, so when the RPM's get above a certain point, it should become fully closed and stay there, and then when it comes down, it will open up to adjust the idle, based on the mechanical idle. I believe it also smoothes the transitions.

Here is my theory on part of your problem... Some of your symptoms are extremely similar to a problem I was having with my EG hatch, and I think your combination of USDM and EDM parts is the cause here.

The USDM IACV is dependent upon the adjustable idle passage for correct operation.

If you took the idle screw and tightened it fully, you will start to have the warmed up issues you are having.

My hatch used to die and stall on me all the time once it was warm. I couldn't figure out why, so I started troubleshooting. The idle screw was fully closed. Readjusting according to procedure cured the issue.

Apparently, the ECU uses the IACV primarily to smooth out or raise the idle under cold and other certain conditions, but it relies on the idle passage under other circumstances. Since my idle passage was fully closed, the engine would die when in neutral, and sometimes when sitting for awhile idling. The ECU was assuming that the mechanical idle was correct and was doing its thing.

I think this is a big part of your problem. The idle passage primarily keeps the car running, with the IACV adjusting for conditions as necessary. That is also why mechanical idle must be set with the IACV disconnected. It is the primary, not vice versa.

Since you don't have a mechanical idle passage, the solution is something you will have to decide on. Perhaps a USDM throttle body could be implemented. I am sure the EURO-R IACV and ECU were designed to compensate for the difference because the programmers knew there was no mechanical passage, but a USDM ECU would not be, as they were all equipped with the adjustment screw.

As far as while you are driving, it is a possibility. I know things can get pretty violent if you drive around with the IACV disconnected, so I would imagine they could get bad if the IACV were failing or not operating the way the ECU thinks it should. While I was testing the EG, I drove around with it disconnected for a time, and it could get downright violent if the throttle position changed to rapidly. With a really slow change, I could get it to be almost undetectable, but if I just pulled my foot, it was VERY violent.

I think if it were me, my first step would be to find a USDM throttle body and see if that will work. If the mechanical passage eliminates your issue, then you have found the problem, if it eliminates or alleviates some, you have found part of the problem.

Honestly, with your setup, it will probably take a long time because there were so many variables introduced at once. The only solution I can think of is to eliminate them 1 by 1, and see where you end up.

[cp[mike]]

awesome scott, thats the kind of feedback i was hoping for.

like you said, theres no mechanical passageway. and to be honest, ive still been wondering how the ECU manages to keep a (relatively) steady idle entirely on its own, when it wasnt originally programmed to do so.

i need to look into using a USDM throttle body, but i dont think it will work. i used a USDM 2001 prelude TB gasket, and it matched up besides the FIV ports and crap at the bottom... i had to cut part off and fill in gaps with hondabond. so that would lead me to believe the OBD2 throttle body wouldnt work. im also using the TB mounted MAP sensor, but i have extra ones and i could leave one hanging connected via a line if need be. i dont think an OBD1 throttle body would work, based on what ive read, i think the bolt pattern is different. ive heard of people cutting and welding to get their original H22 TB to fit on their new euro R manifold.

it seems the problems get progressively worse the hotter the engine is. itll drive fine for 10-15 minutes, then itll start doing oddball things. it stalled at a light, had a hard time starting, and then from there it would hesistate and hiccup more than usual. occasionally, in 2nd gear (acclerating), id feel a violant jerk as the car lost power, RPMs dropped (by... 300rpm?), and then instantly kicked back in. i got it home, left it sitting in the driveway for a minute, and it stalled. thats when i first noticed the IACV was buzzing... car off, on, and off again, and the buzzing is gone. while buzzing, itd stop if i disconnected the plug, and start again if i hooked it back up. i dont doubt that if i go out and start driving it right now, itd be fine and problem free for at least 15 minutes. fortunately my ride back and forth to work is only 20 minutes

im pretty familiar with adjusting and correcting idle properly. i just wish i had an idle screw, because without it, the helms troubleshooting and idle adjustment procedures are pretty irrelevant lol.

as far as narrowing it down bit by bit, im slowly working on that. my ignitor started crapping out on me not long ago, it took a period of a month or so to get bad enough. now it looks like my IACV is following right behind it.

my ignition seems to be fine, but im going to completely cross that off the list once i get the MSD hooked up and firing strong.

ive been having fuel issues too, though... my gauge is now reading too high, now at 1/4, the tank is near empty to the point of not being able to start once turned off. it was having completely erratic starting/not starting problems, which i thought were fixed by the ignitor, but it ended up being a dying main relay which would only cause problems if i had the floor vents blasting heat for a while. (THAT was a pain to diagnose... lol)

so im not sure whats causing my car to slowly fall apart, but it looks like the only things dying are the things that i reused during the revamp of the engine bay. i replaced most things, minus the IACV, FPR, fuel pump, and stuff like the main relay. walbro and a new FPR as well as inspecting the tank and level sending unit will ease my mind as far as fuel delivery goes.

[owequitit]

awesome scott, thats the kind of feedback i was hoping for.

like you said, theres no mechanical passageway. and to be honest, ive still been wondering how the ECU manages to keep a (relatively) steady idle entirely on its own, when it wasnt originally programmed to do so.

i need to look into using a USDM throttle body, but i dont think it will work. i used a USDM 2001 prelude TB gasket, and it matched up besides the FIV ports and crap at the bottom... i had to cut part off and fill in gaps with hondabond. so that would lead me to believe the OBD2 throttle body wouldnt work. im also using the TB mounted MAP sensor, but i have extra ones and i could leave one hanging connected via a line if need be. i dont think an OBD1 throttle body would work, based on what ive read, i think the bolt pattern is different. ive heard of people cutting and welding to get their original H22 TB to fit on their new euro R manifold.

it seems the problems get progressively worse the hotter the engine is. itll drive fine for 10-15 minutes, then itll start doing oddball things. it stalled at a light, had a hard time starting, and then from there it would hesistate and hiccup more than usual. occasionally, in 2nd gear (acclerating), id feel a violant jerk as the car lost power, RPMs dropped (by... 300rpm?), and then instantly kicked back in. i got it home, left it sitting in the driveway for a minute, and it stalled. thats when i first noticed the IACV was buzzing... car off, on, and off again, and the buzzing is gone. while buzzing, itd stop if i disconnected the plug, and start again if i hooked it back up. i dont doubt that if i go out and start driving it right now, itd be fine and problem free for at least 15 minutes. fortunately my ride back and forth to work is only 20 minutes

im pretty familiar with adjusting and correcting idle properly. i just wish i had an idle screw, because without it, the helms troubleshooting and idle adjustment procedures are pretty irrelevant lol.

as far as narrowing it down bit by bit, im slowly working on that. my ignitor started crapping out on me not long ago, it took a period of a month or so to get bad enough. now it looks like my IACV is following right behind it.

my ignition seems to be fine, but im going to completely cross that off the list once i get the MSD hooked up and firing strong.

ive been having fuel issues too, though... my gauge is now reading too high, now at 1/4, the tank is near empty to the point of not being able to start once turned off. it was having completely erratic starting/not starting problems, which i thought were fixed by the ignitor, but it ended up being a dying main relay which would only cause problems if i had the floor vents blasting heat for a while. (THAT was a pain to diagnose... lol)

so im not sure whats causing my car to slowly fall apart, but it looks like the only things dying are the things that i reused during the revamp of the engine bay. i replaced most things, minus the IACV, FPR, fuel pump, and stuff like the main relay. walbro and a new FPR as well as inspecting the tank and level sending unit will ease my mind as far as fuel delivery goes.

LOL! Fun Fun.

I wasn't trying to imply that you couldn't troubleshoot, so I hope you don't think that! I have seen very seasoned mechanics adjust it with the IACV connected though because they assumed that it had to be working in order to get a correct idle. I was just making sure the base was covered.

Hope you don't take offense to that. When we troubleshoot an airplane, it is understood that both people know what is going on, but we coherently and cohesively go through and eliminate all variables in a particular fashion, to isolate the cause, even if it means asking and answering a question we both know the answer too. No offense intended.

Does the car die completely if you unplug the IACV while it is running?

As far as the TB compatibility, I can't say that I know for sure what works and what doesn't. I would recommend sending a PM to 2point6 on that one.

He had a Euro-R on his car quite a ways back, and even had a very good write up on what was needed to make it work.

My guess would be this: If the USDM TB IACV passage lines up on the Euro-R, maybe try that first. The only 3 passages that absolutely have to exist are the IACV, the idle port, and the MAP port. We have in the past eliminated everything else with no issue. I don't know how you would make it work, but at least it would remove the variable of the idle passage.

Then if it is still acting up, I would progress to the IACV. It is very possible that it is going too. Like you said, it may just be a bunch of problems that are occuring one right after the other.

Between the TB and IACV, you should be able to solve the idle and dying problem, because those are about the only 2 variables that should effect it, that haven't already been accounted for. Fuel for idle shouldn't be an issue, because it runs fine at higher fuel demands.

From there I would move onto the ignition, and then I think I would attack the fuel last. The pressure regulators and pump etc, aren't likely to just fail, unless they have TONS of miles on them. I don't know the specific nature of the parts though, so I would say which one to do second is a judgement call.

Maybe the base H22 maps are WAAY off in some places.

That "jerking" while driving, still sounds like it COULD be an IACV issue to me. The EG would jerk so violently with it disconnected, it was equivalent to hitting something or slamming on the brakes. I mean it was almost painful, and it was almost impossible to drive. Even small corrections under the right conditions would cause it.

[93accordexcoupe]

i didnt read through all of the posts cause im really lazy. but it does have an electrical connection. are the connections all good? cause ive had sensors buzz before and after checking each connection i noticed they were filthy. new sensor's made the buzz go away. kinda sounded like that HID buzz that u sometimes get with a kit.

[cp[mike]]

sorry i missed the last two posts.

scott - no, i didnt take offense at all. best way to diagnose is start with the basics, step by step, even if its assumed - thats how stupid mistakes are found. and yes when it would jerk/buck, the first time i felt it i actually turned around to see if the guy behind me had hit me. its happened a couple times, both times were in 2nd gear, coming from a stop.

travis - filthy connections? hah, right.

anyway i hope the problem is now fixed. i threw an IACV from an f22 on it, and it holds a very steady idle, and i didnt notice any issues driving to work this morning. i guess time will tell. the f22 ports and bolt holes lined up, so with a pair of longer bolts and rerouting my coolant lines, the new valve was installed in a couple minutes. the coolant nipples point different directions, but that doesnt matter, my coolant lines arent pre-moulded, so i can move them wherever i want.

[93accordexcoupe]

travis - filthy connections? hah, right.

haha oh yea, i forgot what engine bay this motor is in

[BIEN_DIESEL]

its an easy fix

[93accordexcoupe]

its an easy fix

what is it then

[cp[mike]]

its an easy fix

maybe i should just go ahead and try replacing it, right?

[BIEN_DIESEL]

im not there to see and hear the prob but when i have idle surge and crap. i open the thermal wax valve behind the throttle body and take a screw driver and twist it to tighten it as hard as i can, when it gets loose, it makes the idle go nut, then under the throttle body is that cap with 2 coolant line runign thru it, i open it and took the spring apart and keep it spreaded apart. the best way for me, i have no coolant lines or any shit touching or going in or out of my inatke manifold nor my throttle body, ill take a pic of it one day

[cp[mike]]

longer bolts = random bolts from my huge box

and yes it fixed my problem, i had no idle issues afterward.

[owequitit]

Hey Mike, I just wanted to let you know that I have been reading into this more just for curiosity's sake, and for my own potential mod list.

Apparently, the S2K TB is almost a direct swap onto the Euro R. I believe some minor porting is required because it is a 64MM TB vs 62MM, but it may have the idle passage.

**edit** after just looking it up, it does not appear to have the idle passage, but perhaps you could find some version of it that does**

I suppose it isn't a critical priority at this exact moment, but it is something you can work on.