RockinthEFhatch

I'm tired of seeing everyone ask the same question so here's a general list of things to do to troubleshoot your idle, focusing mainly on servicing the "FITV" (Fast Idle Thermo Valve). Also, if you have a bad thermostat this is the time to install a new one as you need the car to be able to reach normal operating temperature. EDIT: I forgot to mention to also make sure your valves are adjusted to spec as that could also aid in poor idling.

If your idle is stable but either too high or low then you need to adjust it with the idle screw, but don't just turn the screw blindly! The correct way to do it is by letting your car warm up then, while the engine is running, disconnect the IACV (Idle Air Control Valve) electrical plug behind the intake manifold, and adjust the idle screw to 800rpm. After doing that turn your car off, reconnect the IACV plug, then disconnect the battery for a couple of minutes to reset the ECU because you will have a CEL, doing this will get rid of that CEL. Connect the battery and your Idle should be at its normal range - 800 +/- 50 rpm

Most of the time, erratic Idle is caused by a disturbance in the vacuum system, the engine will continuously try to compensate for the loss or gain of air coming into the intake. When you start your car and the engine idles, air bypasses the throttle plate through a couple of holes, one from the FITV and the other from the IACV. The purpose of the FITV is to let extra air in when the engine is cold to help it idle and retain the proper A/F ratio. After the engine is at normal operating temperature, coolant flowing through a thermostat in the FITV heats up a substance inside it which pushes a little plunger that closes the valve that's letting air through on the other side, at that time the IACV will control the idle. The main difference between both of these systems is that the FITV is mechanically controlled and the IACV is computer controlled.

So the first thing you should look for is any apparent leaks from vacuum hoses, bad seals, improperly tightened mating surfaces on the TB (throttle body), IM (intake manifold), etc. If everything checks out move on to the IACV, unbolt the 2 12mm bolts holding it in place then separate it from the IM. It should look like this:


Note the two holes in it; the one you are mostly concerned with is the hole with the screen on it. Make sure it is not clogged or otherwise obstructed by debris. If it is you can clean it up with brake cleaner. Bolt it back onto the IM and reconnect any hoses or the electrical plug you may have taken off of it.

Now we will move on to servicing the FITV. You don't want to keep spending money on your 17+ year old Honda especially since you're thing only one in your family who likes the car so here's how to check and service it so that you don't have to go buy a FITV

1. Separate your intake tube from the TB and look inside, you will see 2 holes. The top goes to the IACV and the bottom goes to the FITV.


2. Start your car and let it warm up to normal operating temperature (fan comes on), then plug the FITV hole, there should be ZERO to VERY MINIMAL suction. If there is suction after warm up then there is something wrong with the FIT valve, turn the car off and let it cool down.


3. This is where the manuals tell you to change the FIT valve with a new one, but there are actually a couple of things you can do to restore your old one. First things first, this is what the FITV looks like, it's attached to the underside of the TB or in some models it will be attached on the manifold right under the TB and it may have 2 coolant hoses, mine had one on the FITV and one going to the IACV from the TB (channeled through the FITV):


4. Disconnect any coolant hoses, vacuum lines, and electrical connectors that may be in the way of the back of the FITV (make sure you mark them so you know where to reconnect them). Now look at the back of the FIT valve, there is a flat plate held down by 2 screws, you'll be removing this plate. Due to the limited space/visibility I used a mirror and an elbowed screwdriver to take it off, you can also use an 8mm socket:


Inside is the end portion of the spring loaded valve, held down by a white plastic piece with 2 slots on either side:


5. This piece is threaded like a screw and sometimes it will unscrew over time, creating too much slack on the spring of the valve and therefore causing a vacuum leak. Screw it back in with any tool that fits the slots. Screw it in tight but don't overdo it.


6. Replace the plate and reconnect everything you had taken off.

7. Repeat the procedure for checking suction at the FITV hole on the TB [STEP 2]

RockinthEFhatch

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Modified by RockinthEFhatch at 10:23 AM 5/7/2008

Maxcapacity

http://www.ef-honda.com/ben/Badidle.php
This also very helpfull.

G0crxG0

I have 2 CRX's both having idling issues

If this solves them, I may just have to buy your steering wheel to say thanks

RockinthEFhatch

Haha, thanks man I appreciate that and I'd really love to sell the steering wheel

slow hatch

Going to try this in a few minutes Already checked my IACV, but not the FITV. THanks

Jonny Rocket

I didnt know about that FITV...hmmm I'll look into that.

pumpkinkidd

slow hatch

This fixed my problem, I now have a normal car again woot woot. Other than the open downpipe

ComeOnKip

I blocked the FITV valve when its hot, it seemed to help the idle temporarily but after letting it run for a few minutes ( while up to temperature ) the idle started going erratic again (all of this is on an OBD0 b16). My IACV screen is clean.... could it just actually be the IACV itself? If so, what do I replace this with? 90-93 Integra IACV? thanks for a great write up.

RockinthEFhatch

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slow hatch &raquo;</TD></TR><TR><TD CLASS="quote"> This fixed my problem, I now have a normal car again woot woot. Other than the open downpipe </TD></TR></TABLE>
That's what I like to hear!

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ComeOnKip &raquo;</TD></TR><TR><TD CLASS="quote">I blocked the FITV valve when its hot, it seemed to help the idle temporarily but after letting it run for a few minutes ( while up to temperature ) the idle started going erratic again (all of this is on an OBD0 b16). My IACV screen is clean.... could it just actually be the IACV itself? If so, what do I replace this with? 90-93 Integra IACV? thanks for a great write up.</TD></TR></TABLE>

Try replacing the IACV with a new one I suppose, I mean I've never encountered any problems when repairing them as far as my write-up goes, but there's a chance you just need a new one.

crxricer66

didnt knoe aobut the fitv. im gonna go try it. awesome write up man

P a r i s h

good sheyt!

gib

This is a great post. From my point of view, there is one small problem. My DOHC ZC, in a 1985 Civic Si 1.6L that was originally sold in the Japanese domestic market and imported used to NZ, has a different inlet manifold. It does not have the two holes you describe (and show in the pics). There is a small throat inside the main IM throat, at the top, which could be used by the FITV. The FITV is the same, but mounted differently. It is vertical, and the top plate is readily accessible, just behind the IM. Do you know this engine?

I have screwed the plastic piece in the FITV down, and that helped. Before the idle revs were cycling between 1500 and 2200, now it's between 1000 and 1500. My question is this: does my engine have an IACV, and if so, where is it?

thanks
Gib

doom26464

tried this And I was able to turn it like 1/8 to about 1/4 so it was already pretty snug. Didn't fix the idel and its still sucking when warm so guess im going to try replacing it next.

fluxuator

I just had to do this today... I have a 91 CRX Si with a B16 and one morning my idle shot to 3K upon startup and after warmup would hover around 1.5K with occasional pulsing of the idle (up to 2K at times)... freaked me out thought my timing was off (it wasnt) which made things worse... found this guide and the REX is alive and well!

I will HIGHLY recommend just taking off the FITV (3 10MM bolts- then hand tighten as i couldnt find any torque specs) as it is MUCH easier to tighten the white plastic insert with it off... plus it gave me a chance to clean everything out. I just used my hand to get it as tight as I could then loosened 1/4. bolted everything back on and now my startup idle is around 1.5 (cold) and then comes back down to 800...

Excellent Guide

EDIT: forgot to mention that air is still getting sucked through the FITV after warmup but it does not appear to do anything to the idle nor does the suction feel as strong as before... I placed my finger over the FITV hole on the TB and there was still suction... Idle is still good... so I'm happy


Modified by fluxuator at 5:05 PM 6/7/2008

lsvtecdc2teg

would this also help with a rough idle that bounces from 1,000 to 1500? 1500 to 2000 in colder starts?

r1de4life

my car makes this really obnoxious humming noise almost like a cow at idle lol, the manifold is from a auto also. any ideas what it is, car is a 91 dx mpfi converted also.

r1de4life

if i plug up my iac hole in my throttle body almost all the way closed it stops making the buzzing noise and idles normally

Pworld925

my car fluctuates at idle when warm too, so today i tried to plug the hole to the FITV and it kept fluctuating, but when i plugged the IACV hole, it idled normal!

just wondering what i can do now to keep idle normal, should i take the IACV off and clean it or buy a new one?

PatrickFrantz

ok i purchased a 1991 DX ef hatchback yesterday from a buddy of mine. it runs great when its cold but when it starts to get warm it acts like it is gunna die out an loads up with fuel. if i rev it up it seems to run good but if it jus sits there an idles it starts to chug out an eventually will die!

it recently had the head gasket replaced as well. guy who i bought it from said he thinks the timing is off a tooth but in the past if a sohc is off a tooth it wont idle right at all.

can anyone help!! also its dual point (GAY i know)

lancerkid06

what id you dont have a fitv. would that make th idle surge? i looked where you said it would be but idk if i have one because i dont see what you have in that pic. heres a pic of mine its the best one i have right now ..

Hal9000

No idea on the FITV for you, but in your 2nd pic it looks like you have an unplugged vacuum line and a bolt missing from your throttle body. Have you checked for air leaks?

In my case (stock '88 CRX DX) I'm not sure if I have any of the parts referred to at all since I'm still dealing with the old POS DPFI. I idle is steady but from a cold start it starts around 1750 rpm and it takes a long long time to drop to normal. I commute 8 miles to work and this morning it was still at 1200 when I pulled in and parked.

Any ideas?

lancerkid06

well heres a better pic of under my throttle body. idk what those two nipples go to ... so help me out if you can .. thanks

Furyof4

That is a coolant port that is open which is fine. He has theline looped that would noramally go through the tb to warm it up for cold temps. The missing tb nut may be causing a vauum leak though which would give you a fluctuating idle.

Edit: You have an early tb that does not have the fitv and a later manifold that doesn't have one either.