Can you change the cold-start idle revs (2500 to 2000RPM)?

[EuroDude]

Is it possible to change the cold-start idle RPM level?

On a cold start, the revs start at 2500RPM and slowly go down to ~1000RPM when warm. The thing is that its very noisy at 2500RPM when cold. At 2000RPM it is much quieter (ive already tested it by driving at 2000RPM when cold). Can I simply adjust something on the throttle body? Or is this purely controlled by the ECU?



And wouldnt it be better for the engine to start at 2000RPM anyway? I mean you want the revs to be as low as possible when the engine is cold to avoid wear'n'tear, right?

I would rather it warm up for 10 minutes at 2000RPM, rather than 7 minutes at 2500RPM.


Engine is a D16A8 ZC (1.6L DOHC 16Valve non-VTEC) in a Civic Si 1993

[Limbo]

I believe the cold idle is controlled by the ECU (Not 100% sure on your car)? so you would have to get a new ECU of sorts to fix it.

[crxtasy]

The revs should go down to about 750 when it has warmed up, maybe try re-setting the warm idle rpm and it might fix the cold start rpm.
these pics might help.

http://i32.photobucket.com/albums/d39/crxvtec/tune-up2.jpg

http://i32.photobucket.com/albums/d39/crxvtec/tune-up3.jpg

[huynh12345]

man that happened to me today the engine wouldnt stop ideling @ 2,00rpm and its noisy when i keep it like that for 4-5 minutes

[ECU-MAN]

it is adjustable, I woulndt say easly though

you need to adjust the FITV. then also you risk idle revs hunting

[bennjamin]

perhaps there is an alternate reason for the revs being that high - rather than "adjust" and hope for the best try cleaning the ICAV (located on the rear of the inlet manifold) or as said check the FITV (under the throttle body)

[EuroDude]

Yes the ICAV and/or FITV do need cleaning out because the revs bounce from 2500 to 1500 to 2500 when I start the car. I was quite certain the car always started at 2500, but its been like this for a while so I could be wrong.

@crxtasy, thanks for that pic, im happy with the idle at 1000rpm (good for when I use A/C) but I may try it anyway.



If you guys have a spare second, could you please locate the ICAV and FITV in the pictures below? I have added a grid so you can point out the locations:


PIC1 Top-Front angled view
http://img496.imageshack.us/img496/787/dscf1135a4tv.th.jpg (http://img496.imageshack.us/my.php?image=dscf1135a4tv.jpg)

PIC2 Top view
http://img496.imageshack.us/img496/4742/dscf1136a8ny.th.jpg (http://img496.imageshack.us/my.php?image=dscf1136a8ny.jpg)

PIC3 Front left view
http://img367.imageshack.us/img367/5092/dscf1137a1cd.th.jpg (http://img367.imageshack.us/my.php?image=dscf1137a1cd.jpg)

PIC4 Right view
http://img367.imageshack.us/img367/8913/dscf1138a9jo.th.jpg (http://img367.imageshack.us/my.php?image=dscf1138a9jo.jpg)



My Hayes maintenance manual doesnt have much info about the throttle body at all for some reason. But Ive checked the internet and know basically what to do (For instance just screw the FITV back into its well), I just need to know what to unscrew and pull out on my engine specifically.

thx.

[civiceg9]

The IACV(EACV in digram), there is a hex screw, is 5 side so is not hex, you can adjust that to lower your cold idle. however you will also need to adjust your normal idle.
Takes alot of work to get it right. or just goto the wreckers to see if they have a 2nd hand IACV and just put it on.

[bennjamin]

PIC 1 , Q14/15 + R14/15 is the FITV ~ it is mounted directly onto the bottom of the throttle body.
As you said , you simply need to re-adjust this and reinstall -
to clean the IACV have alook on the back of the inlet manifold next to teh firewall, then peek at my old DIY ( on a d16a8 too)

http://www.ozhonda.com/forum/showthread.php?t=4693

[EuroDude]

@benn, I see, so its that module just below the brass throttle wire/spring. Thanks I'll have a crack at it tomorrow (hopefully not literally) :) I'll check out your DIY as well.

@civiceg9, Ill try the cleaning-up first, then I may adjust the idles. I'm a bit reluctant to do it though since I have no idea how to adjust them both so they work together happily (As ECUMAN said about rev hunting). I may get my mechanic to do that, otherwise if there is a guide on the net, pls let me know.


Thanks all for the help.

[EuroDude]

bennjamin, that DIY is great. Call me a n00b, but is it necessary to remove the negative battery terminal? Is there fuel involved with the IACV functionality or something?

And why the Negative terminal, and not the Positive?
(im guessing because there is risk of a voltage/current surge if the positive terminal is reconnected while the negative is connected)

...just wandering because the Haynes manual I have tells you to disconnect the battery for no apparent reason sometimes (with work that has nothing to do with fuel).

[bennjamin]

just remove it for safety.

[EuroDude]

ok cheers.

[ProECU]

I can modify your ECU to idle both cold & warm wherever you want.

[EuroDude]

I rather not mess with the ECU, plus it sounds expensive and i'm selling the car this year.
But thanks anyway.

[Weq]

the FITV controls cold start. screw the plunger right in and u should get down to 2k when cold.

[EuroDude]

FITV:
"screw the plunger right in" Yep, will do - but I cant get the phillips screws undone :(
I tried using one of those "offset" screw drivers that have a 90degree anglee, but the screwdriver tip size it a tad too small and I risk damaging the screw. I cant use a normal screw driver or an electric drill cause the clearance area is too small.
Is there a special device I can use? Like a 90degree screw-bit adapter that can attach to a standard rachet? :confused:


IACV:
I have cleaned the screen using carby cleaner, it was as dirty as the pic below, but I had problems getting the IACV module completely off so I just sprayed the screen while the two hoses were attached. Hopefully that is ok to do - I have yet to drive the car and test it.
http://tech.ozhonda.com/diy/ICAV_clean/4.JPG

[ProECU]

good luck doing it any other way successfully

[civiceg9]

take your IACV off and go to Bunnings
they have a star type hex key
just try it there and screw it in
thats what I did hehe :D

[ECU-MAN]

what you did to the IACV is ok

the FITV

I use a 1/4 spanner and screw driver bits ( hex type that come on these plug on screw drivers ) to undo the screw, Ill take a pic if you dont know what I mean.

to start with dont go all the way in, start your engine, while its cold, and turn the plunger in just a bit at a time till you knock off 500 rmp. make small adjustments each time remembering what you have done so you can revers the changes if need be.

adjust to how you want it.

once you have the right rpms then off the engine, then put the cover back on and start the engine allow it to warm up

now make sure it doesnt hunt or rev to low or to high.




FITV:
"screw the plunger right in" Yep, will do - but I cant get the phillips screws undone :(
I tried using one of those "offset" screw drivers that have a 90degree anglee, but the screwdriver tip size it a tad too small and I risk damaging the screw. I cant use a normal screw driver or an electric drill cause the clearance area is too small.
Is there a special device I can use? Like a 90degree screw-bit adapter that can attach to a standard rachet? :confused:


IACV:
I have cleaned the screen using carby cleaner, it was as dirty as the pic below, but I had problems getting the IACV module completely off so I just sprayed the screen while the two hoses were attached. Hopefully that is ok to do - I have yet to drive the car and test it.
http://tech.ozhonda.com/diy/ICAV_clean/4.JPG

[EuroDude]

@civiceg9, I managed to clean the IACV screen and the car runs ok, but the same as before. I think the car idles a bit more normal when warmed up but not sure yet as it was intermittent.

ECU-Man, is the 1/4 spanner a fixed-size one that fits the usual hex screw-bits that come with most electric screw drivers? I tried using a variable spanner with no luck (minimal grip). Tomorrow Ill take a screw-bit to the car shop and get a fixed spanner that fits properly and see how that goes. An FITV guide ( http://www.emotors.ca/Articles/97.aspx ) said to insert the plunger all the way in - is this wrong? (their English is broken so its a bit hard to follow).
I think i'm better off trying what you suggested.


cheers.

[EuroDude]

[edit] I got an "Offset rachet screw & socket driver set" from another car shop, will give it a go later.
cheerz.

[Weq]

ummm i just pulled the fitv off (3 bolts under the tb) and adjusted it. couldnt find a screwdriver to undo it while it was on the car. just screw it all the way in imo :)

[EuroDude]

Yeah I know I realised that an hour ago lol, I was trying to just unscrew the rounded cap on the end of the FITV :rolleyes:

Ive taken it apart and cleaned it all up - it had white crusty coolant deposits all over the place and had to use a flathead screwdriver to get it off. A toothbrush wouldnt cut it.

The white knob was all the way at the front (pretty much all the way screwed off), Ive just screwed it all the way back in. Lets hope it idles fine...


ps. Those black rubber seals are too long for the seal seatings and wont go back in properly - does this mean I need to change them? I can get them back in after alot of fiddling, and also put some oil on the edges.




http://img384.imageshack.us/img384/2141/fitva6go.th.jpg (http://img384.imageshack.us/my.php?image=fitva6go.jpg)
http://img384.imageshack.us/img384/4987/fitvb0yu.th.jpg (http://img384.imageshack.us/my.php?image=fitvb0yu.jpg)

[EuroDude]

!!SUCCESS!!

After cleaning and adjusting the FITV (white FITV Knob screwed in tight), its idling perfect now cold and warm!
In fact, cleaning the IACV didnt do much - if anything at all.
Checked for leaks - no leaks at all.



Before
------
Cold = 2500RPM :( (Instantly jerked to 1500 then back to 2500)
Warm = sitting between 1300 and 1600RPM :(, and was hunting for revs occasionally.


After
-----
Cold = 1500RPM :) No jerking, no annoying high revving noise!
Warm = ~900RPM :) All the time now.


[EDIT] well now during warm idle the RPM is dropping a bit too low and causing the headlights and cluster to dim, and the engine gets a bit "chuggy". But ive read that this is due to carbon buildup in the throttle body (arround the butterfly) causing blockage in the idle-air passage way.
I'll clean it out tomorrow and see how that goes. Or maybe I need to rip out the IACV properly and give the whole thing a clean instead of just the screen.

[EuroDude]

The low idling problem is now recified after cleaning the throttle body - it now sits at around 1000RPM, which I know is higher than standard but I prefer it that way.


Thanks for all the help guys, appreciate it :)

[civiceg9]

just adjust the idle screw on the throttle body when engine is warm
turn it until u get to around 700rpm

[EuroDude]

Yeah I tried adjusting the screw while the engine was running warm, but it didnt make any difference at all.

I did more research and my Haynes manual says that you need to unplug the IACV electrical plug, then adjust the idle screw, then replug the IACV plug, and then reset the ECU due to the IACV error code.


... well I am happy with the 1000RPM atm, so I'll leave it as is. At least I know how to adjust it if needed later.



ps. Regarding all that Carbon gunk from the throttle body seeping into the engine (white smoke etc..), where does it go, into the oil or straight out of the exhaust?

...in other words, should I do an oil change?

[JasonGilholme]

your pistons rings will stop any oil coming up over the piston and it will also stop anythin goin down into the block.

If your a bit worried tho an oil change can never go astray.

[EuroDude]

Ok so the gunk just exits through the exhaust.
Its time for an oil change anyway so ill change it.

thx.

[bennjamin]

Ok so the gunk just exits through the exhaust.
Its time for an oil change anyway so ill change it.

thx.

Isnt the "gunk" is pulled in mostly via the PCV in blowby ~ you can clean out the throttle body easy enough but in time it will gunk itself up again. Install a oil catch can on the PCV or replace that with a new one.

[EuroDude]

I was looking into those catch cans a few days ago, but I'm planning on selling the car this year so I wont bother with it. Maybe I'll install one in my new car (looking at a Euro) :)