Lighten flywheel = funny idle ? any ideas

[kayot1k]

Hi there fellas.

had a new clutch/flywheel change over 2 months ago.
was told by mech that my hunting idle was from lighten flywheel ?
and that its common for lighten flywheel, he said some cars have no issues whereas some cars it cant be fixed ?

not that i dont trust my mech but would like others input, if you guys managed to fix the hunting idle if you had one. i tried turning the valve (FITV? i think its called) both anti-clock wise and clock wise to see if it would fix the problem but it still has slight hunt. What i mean is after i dab the accelerator when it drops it hunts for abit before settling.

had this for awhile but this morning was pretty bad after installating my DIY fill mounts kept stalling after a dab of accel. turned the Valve (FITV?) all the way out (closer to me) and it has kinda fix it but now the revs drop really low to 500rpm before creepin back to 750 rpm avg. Hasnt stalled yet since i turned the valve but is feels very close at times.

note, it was fine before clutch change. no aftermarket ecu.

any help would be great
-steve

[dsp26]

nope.. mine didn't and i went to an 8.75lb

[kayot1k]

yeh, i was told it was fine for some and not for others.

might try cleaning throttlebody and IVAC, doubt itll fix the issue since it was fine before clutch change

[TODA AU]

/\ Clean IVAC & throttle is a good idea.:thumbsup:
Was any other work done at the same time as flywheel change?
Major service? Cam belt? Valve clearances?
Normally there is no issue. If there is an issue, it's usually something dumb.
If you get stuck, we can have a look for you.
Cheers

[kayot1k]

lol, adrian the work was done by you. :D
remember green ek4 done about 2months ago approx.

just gearbox work.

[dsp26]

/\ Clean IVAC & throttle is a good idea.:thumbsup:
Was any other work done at the same time as flywheel change?
Major service? Cam belt? Valve clearances?
Normally there is no issue. If there is an issue, it's usually something dumb.
If you get stuck, we can have a look for you.
Cheers

I have a question since you guys do all sorts of work on cars...

I don't understand how the IACV (Intake Air Control Valve) controls the bumpy idle anywhere as much or at all compared to the FITV (Fast Idle Throttle Valve)...

My IACV is bypassed completely with the 2 hoses directly connected and the IACV not even having a block-off plate to TB

***EDIT***
never had idle issues until I re-used my TB gasket and ripped it and just taped it up with 1 layer of electrical tape :p

[TODA AU]

lol, adrian the work was done by you. :D
remember green ek4 done about 2months ago approx.
just gearbox work.

LOL... Sorry, I don't remember everyones online names... :p
But bring it round & I'll see if I can sort it out for you. :thumbsup:
Cheers

[TODA AU]

I have a question since you guys do all sorts of work on cars...
I don't understand how the IACV (Intake Air Control Valve) controls the bumpy anywhere as much or at all compared to the FITV (Fast Idle Throttle Valve)...
My IACV is bypassed completely with the 2 hoses directly connected and the IACV not even having a block-off plate to TB

The IAC (Idle air control) valve is located at the back of the intake manifold.
It is controls the amount of air bypassing the throttle in response to a signal sent from the ECU. Its purpose is to maintain a steady idle.
It does this by internally bypassing air past the throttle into the manifold.
The ports that the air travels through are internal to the throttle & manifold.
(One is easily seen as the upper port just forward of the throttle plate)
The external lines are coolant to aid in cold start.
This works in conjunction with idle ignition control.
Idle ignition control is triggered by TPS (Throttle position sensor) & under x rpm
Similar to overrun fuel cut function. (TPS + MAP + RPM)

The FITV (Fast idle throttle valve) is located under the throttle body on older B16A engines. It is not found on late model or OBD2 B-series engines.
It has a Teflon seat** that is threaded to seat against the wax thermostat behind. When cold, the thermostat is retracted allowing air to bypass the throttle & give a high idle when cold. As the coolant temp increases, the wax thermostat closes of reducing the idle back to hot idle speed set by idle bleed bypass screw on throttle & IACV.

** It is this Teflon seat that becomes loose over time & migrates away from the wax thermostat causing air to bypass even when the engine is at operating temp.
This can cause high or hunting idle.

Hope that helps.

[Limbo]

when i did mine had no issues

[dsp26]

oh yeah sorry... I got them the other way around.... so then can you please explain an answer with the 2 items reversed...

How is cleaning the FITV any help... though you didn't suggest (as i originally thought since i had it the other way around) since i've seen a DIY to clean it on more than one forum...


***EDIT***
sorry you did answer it in the last paragraph.... :)
so it isn't even possible to 'clean' the FITV by your explanation of its mechanical functionality?




The IAC (Idle air control) valve is located at the back of the intake manifold.
It is controls the amount of air bypassing the throttle in response to a signal sent from the ECU. Its purpose is to maintain a steady idle.
It does this by internally bypassing air past the throttle into the manifold.
The ports that the air travels through are internal to the throttle & manifold.
(One is easily seen as the upper port just forward of the throttle plate)
The external lines are coolant to aid in cold start.
This works in conjunction with idle ignition control.
Idle ignition control is triggered by TPS (Throttle position sensor) & under x rpm
Similar to overrun fuel cut function. (TPS + MAP + RPM)

The FITV (Fast idle throttle valve) is located under the throttle body on older B16A engines. It is not found on late model or OBD2 B-series engines.
It has a Teflon seat** that is threaded to seat against the wax thermostat behind. When cold, the thermostat is retracted allowing air to bypass the throttle & give a high idle when cold. As the coolant temp increases, the wax thermostat closes of reducing the idle back to hot idle speed set by idle bleed bypass screw on throttle & IACV.

** It is this Teflon seat that becomes loose over time & migrates away from the wax thermostat causing air to bypass even when the engine is at operating temp.
This can cause high or hunting idle.

Hope that helps.

[bennjamin]

a flywheel has no change in idle.
The cars idle is set by ECU and a few varibles ~

[kayot1k]

yeh thought so might just be my car.
that problem probably happened same time i got my clutch change so i assume they were related.

thats rules that out, if anything ill come give u a visit adro on the weekend if i cant fix it myself.

[bennjamin]

its more than likely related to the clutch change visit....just not the clutch or flywheel itself.
More than likely something is loose (vacuum leak) or perhaps your ECU is on constant limp mode ?
Go back to the installer and get em to fix it

[TODA AU]

so it isn't even possible to 'clean' the FITV by your explanation of its mechanical functionality?

The FITV can become clogged with crap, to clean it it needs to be removed & disassembled.
The end plate is removed to expose one end of the teflon seat.
Wind the seat out & clean all parts with carby clean or similar & a pipe cleaner or wire brush.
When reinstalling teflon seat, take care not to damage it. (Use large flat blade screw driver)
It works best with a little loctite added to the thread so it doesn't come loose.

[JohnL]

The IAC (Idle air control) valve is located at the back of the intake manifold.
It is controls the amount of air bypassing the throttle in response to a signal sent from the ECU. Its purpose is to maintain a steady idle. It does this by internally bypassing air past the throttle into the manifold.

The IACV also smooths out the transition between injectors 'on' and injectors 'off' with the engine on the overun (i.e. an overun condition as you get when you back off in gear or briefly get when changing gear) or at very light throttle at higher speed / rpm and on the cusp of the fuel cut out cutting in (if you follow), i.e. it smooths out on / off throttle behaviour to avoid drivetrain harshness, I assume because it doesn't allow the MAP sensor to see a high vaccuum the moment the throttle is shut or nearly shut.

It can also cause an annoying problem related to this whereby the engine rpm drop too slowly when upshifting causing a slow and / or less than smooth gearchange, and / or for the rpm to momentarily to 'hang' at higher rpm with no drop as soon as you're off the the throttle and have the clutch pedal pushed in, or even for the rpm to momentarily 'jump' slightly in this circumstance (really irritating!). If the engine does this it affects gear shifting adversely. I have a fix for this if anyone is having this problem and is interested, just ask.


The external lines are coolant to aid in cold start.

My understanding is that it's to assist in lessening the IACV from icing up in very cold conditions, or at least to 'de-ice' more quickly if it does ice up. Same deal for the coolant lines to the throttle body. Disconnecting the coolant lines shouldn't affect it's function in temperate or tropical climates.

The FITV is supposed to operate from coolant temp from the coolant lines, but mine currently aren't connected and it seems to make no difference to when they are (?).

[dsp26]

The FITV is supposed to operate from coolant temp from the coolant lines, but mine currently aren't connected and it seems to make no difference to when they are (?).

Ditto... which is why i'm wondering why this is attributed to "hunting idle" issues...

the coolant lines going to/from aren't even pressurised (my connectors aren't even clamped) so i don't see what of it can affect idle...

My car still idles high when cold and drops to warm idle

[TODA AU]

My understanding is that it's to assist in lessening the IACV from icing up in very cold conditions, or at least to 'de-ice' more quickly if it does ice up. Same deal for the coolant lines to the throttle body. Disconnecting the coolant lines shouldn't affect it's function in temperate or tropical climates.

The FITV is supposed to operate from coolant temp from the coolant lines, but mine currently aren't connected and it seems to make no difference to when they are (?).

Agreed, the water lines are suposed to be for cold start on FITV & de-ice for IACV (& throttle - OBD2)
My bad in previous post, typed too fast & got muddled.

Regarding FITV.
I've only encountered this device causeing problems when the teflon seat has become loose & moved away from the thermostat valve. Otherwise it seems to work as you say with or without the water. Perhaps the heat transfer to the manifold is sufficient & the water is only anti ice in any case?

*Edit*
Details of valve from Honda is here:
http://www.hondatech.com.au/forum/attachment.php?attachmentid=668&d=1202877893

[TODA AU]

LOL... Sorry about the size :p

[JohnL]

Regarding FITV.
Otherwise it seems to work as you say with or without the water. Perhaps the heat transfer to the manifold is sufficient & the water is only anti ice in any case?


Seems possible, at least on available evidence...

I definitely do get a highish idle speed when cold which goes away when at correct temp. I used to put this down to the IACV, but the more I think about it the less likely it seems that this is actually an IACV function. I suspect the IACV could be used for this purpose (cold idle increase) if Honda chose to set it up to do so, thus avoiding the need to have a seperate FITV. I wonder why they didn't?

[JohnL]

Ditto... which is why i'm wondering why this is attributed to "hunting idle" issues...

If you want to eliminate the FITV as a possible cause of a 'hunting' idle, then you could use some shim between the FITV and plenum to blank off the FITV ports (fit shim using a little non hardening gasket sealant).


the coolant lines going to/from aren't even pressurised (my connectors aren't even clamped) so i don't see what of it can affect idle...

The lack of clamps not causing the lines to pop off isn't necessarily a sign that the lines aren't getting pressurised. But, if the coolant lines to the FITV aren't becoming pressurised then there may be a substantial blockage in the coolant lines (would have to be both lines).


My car still idles high when cold and drops to warm idle

Then the FITV must be functioning as per speculation of heat soak through the metal, I think...

[bennjamin]

guys please make a new thread about "removing FITV".

Otherwise lets keep it on topic to why this car has funny idle after a clutch / flywheel install

[JohnL]

guys please make a new thread about "removing FITV". Otherwise lets keep it on topic to why this car has funny idle after a clutch / flywheel install

Bennjamin,
I think you're assuming that his idling problem is actually directly related to the flywheel installation as the OP seemed to be assuming, which it quite probably isn't (IMO). We are (at least I am, I won't speak for other people) exploring other possibilities that might (or might not) be the real cause of the problem.

It might be more problematic to make a new thread every time a discussion veers a bit away from being a 100% literal response to a question, especially if the original question is possibly not quite the right question...

[bennjamin]

you are right I am assuming its directly related to the install , only because it became apparent after ~ altho more so when he installed mounts.
The discussion above was aimed more at the post http://www.ozhonda.com/forum/showpost.php?p=1538230&postcount=6
it is relevant to this query but lets try to tie it in with the original thread starter rather than another query.

[kayot1k]

HEhehe, i did think it was related to the FLYWHEEL since it was lighter than stock, had thought the flywheel was some sort of harmonic balancer and in changing the weight it affected my idle ..... guess the replies a veering away from actual thread question but is directly related to my query about idle. dsp26 just decided to hi-jack my thread and ask his own questions. but thats ok cus his helping me get an understanding of what COULD be problem. if you want you could change the title of the thread Benn.

lol, anyways just for progress sake, i cleaned out my throttle body and IACV thanks to bens DIY i found way back.... IACV was way dirty.

no change in hunting, just turned out the FITV valve alittle more , doesnt get to the state where it wants to stall any more just when i blimp the accelerator it drops back to idle rpm then to something like 1k and slowly back down to idle (slight hunt something like 200-300rpm hunt before settling). Is this normal for lighten flywheel ? or is this a case of FITV/IACV problem affecting idle as Adrian was saying teflon seat. i mean overall drivability is normal if you dont realise the rpm hunt so im not to worried about this atm but would like to correct it if it was easy enough.

[bennjamin]

Not normal for a lightened flwheel ~ The characteristics are actually the opposite where the revs will try to drop to exactly idle as quickly as possible :)
Try and swap FITV or ICAV for a known good working one ( from a mate with a ek4) and see if that fixes any issues.
Also , checked your gearbox ground is tight ?

[kayot1k]

sorry?? gearbox ground is tight? what is this

[bennjamin]

gearbox ground ~ its a earthing ground located close to your clutch line , near the front DRIVERS SIDE torque mount. Might be loose making some sort of issue with revs ?

[JohnL]

HEhehe, i did think it was related to the FLYWHEEL since it was lighter than stock, had thought the flywheel was some sort of harmonic balancer and in changing the weight it affected my idle .....

A light flywheel may cause a rougher idle because the flywheel mass may not be great enough to adequately 'smooth out' the firing impulses from the cylinders (two power strokes per crank revolution with a four cylinder engine). Each time the engine fires it speeds up slightly then slows slightly until the next power stroke.

The two power strokes per revolution do overlap each other, but the power creation and thus rotational speed of the crank within each crank revolution still isn't entirely smooth, causing vibration. A heavier flywheel masks this affect by making it harder for each power stroke to increase momentary crank speed, and for the crank to lose momentary speed.

Fitting a lighter flywheel will reduce this masking affect and increase rpm speed fluctuation that occurs within each crank revolution, which is why a lighter flywheel can sometimes cause a 'rattle' in the gearbox at idle (despite being in neutral the gears on the cluster gear still rattle back and forth against the gears on the mainshaft twice every revolution of the crank).

This is more of a problem the fewer cylinders there are, i.e. with a six cylinder engine thre are three overlapping power strokes per revolution and with an eight cylinder there are four power strokes, giving a more even power delivery and less vibration at idle. Single cylinder engines require very heavy flywheels relative to their capacity to achieve an acceptably smooth idle, single cylinder engines with a light flywheel (or none) vibrate a LOT (kart engines buzz your kidneys and other body parts at low rpm).

The idle may be slightly rougher with a lighter flywheel, but it won't cause the engine to 'hunt' up and down. However, a light flywheel will tend to make the idle speed more immediately responsive to any air flow 'corrections' created by the IACV.

From what you've said I can't see the flywheel being resposible for the problem. It does sound air flow related to me...