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Discussion Starter · #1 ·
Do you have erratic, loping, searching, bouncing, or however you'd like to call it, idle problems? Here's a general list of things to do to troubleshoot your idle, focusing mainly on servicing the "FITV" (Fast Idle Thermo Valve). This tutorial assumes you have no CEL (check engine light) codes, you must take care of those first (chances are that's part of the idle problem). 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...

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 (wait until the fan comes on) then, while the engine is running, disconnect the IACV (Idle Air Control Valve) electrical plug behind the intake manifold, then 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. Recconect the battery and your Idle should be at its normal range (usually around 650rpm). Idle control screw location: refer to post #76 (http://www.superhonda.com/forum/3991603-post76.html).

Most of the time, erratic Idle is caused by a disturbance in the vacuum system, the engine will continiously try to compensate for the gain and loss of extra 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/attain the right A/F ratio; after the engine is at normal operating temperature, hot 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 (that's why it's connected to the harness).

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 2 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 carb/intake cleaner. Bolt it back onto the IM and reconnect any hoses or the electrical plug you may have taken off of it.

EDIT: I forgot to mention to also make sure your valves are adjusted to spec. Yes, valve lash (improperly adjusted intake/exhaust valves) can cause erratic idle.

Now we will move on to servicing the FITV. Most of the manuals you read tell you that if you suspect the FITV to be the culprit of your bad idle, you should throw it away and buy a new one... I'll show you how to check and service it so that you don't have to go and spend money unnecessarily on a new FIT valve.

Part I

1. Separate your intake tube from the TB and look inside, you will see 2 holes... the picture below is self explanatory:


2. Now start your car and let it warm up to normal operating temperature (fan comes on), then put your finger in the FITV hole, there should be ZERO to VERY MINIMAL suction:


3. 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.

4. 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 "fix" it. 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 has one on the FITV and one going to the IACV from the TB (channeled through the FITV):


5. 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):


6. 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:


This is the FITV plate in an exploded view image on a GSR manifold:


7. 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:



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


9. 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 (I used the flathead side of my elbowed screwdriver, turning it clockwise):


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

11. Repeat the procedure for checking suction at the FITV hole on the TB (Steps 1-3). If there is still a lot of vacuum in the FITV hole, go to "Part II" below.
 

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Discussion Starter · #2 ·
Part II

At this point all there is to do with the FIT valve that's within your capabilities is to check that the plunger inside the FITV thermostat is working properly, and if possible replace with a new plunger.

1. First let the engine cool down, then disconnect the coolant hoses attached to the FITV:


2. There are 3 10mm bolts holding the FITV in place (note I used a mirror so you can see them from underneath):


3. Remove the FITV from the TB:


4. Remove the FITV thermostat housing (held down by 2 phillips screws), be careful not to tear the O ring inside:


5. You should see the thermostat (brass piece) and the springloaded valve recessed inside against the plunger:


6. Now here's the fun part, get a lighter and hold it on the thermostat for about a minute:


7. While looking into the chamber where the plunger is, you should see it slowly pushing the valve closed as it heats up:


I happened to have a spare FITV from another manifold so I was able to swap plunger/thermostat assemblies, I had to swap the plungers as opposed to the whole FITV because the configuration of hoses and bolt pattern was different, but the thermostat/plunger is the same...


8. Unscrew the the thermostat/plunger assembly from the donor FITV with large pliers or arc joint, take care not to damage the assembly too much as it is made from brass (you don't want brass floating around your cooling system):


Compare both plungers. In my case the old plunger was leaking the heat reacting fluid thus not having enough of it to expand and push the plunger all the way out to close the valve completely:


9. Screw the 'new' thermostat/plunger in and tighten with the pliers.

10. Reinstall everything back in and check for suction after the engine is warmed up, you shouldn't have any.

If after all of this you still have suction from the FITV (after engine is warm) you're SOL and need a new FIT valve. If this fixed your FITV but not your erratic idle then you may need a new IACV. Good Luck!


~THE END~
 

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Discussion Starter · #5 ·
No problem, it just pisses me off that you have to look through all kinds of different resources to find this information, and there are never pictures to illustrate the steps... Since I had to do this procedure recently, I figured why not make it a little easier for people to find it in one place :)
 

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Discussion Starter · #8 ·
hobie237 said:
And we get a thread about it what? Twice a week? LOL.

If it's a sticky, it's getting a link in my sig.
True, that's another reason, people are often asking idle related questions...
 

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Discussion Starter · #17 ·
NutromiX said:
So what happens when you don't have a Fast Idle Control Valve like with a Skunk2 Throttle Body! :D
I have an answer to that but it would be theoretical, I don't have time right now but i'll get back to you later on that...
 

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Discussion Starter · #22 ·
NutromiX said:
So what happens when you don't have a Fast Idle Control Valve like with a Skunk2 Throttle Body! :D
Follow manufacturers instructions, this write up is for STOCK throttle bodies, which is what most people have.

How does it idle? if it idles fine then it must have other means for controlling idle during cold starts...
 

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Discussion Starter · #23 ·
91Vtec said:
there should be no idle whats so ever right, even when its not hot?
You mean suction through the FITV hole? there should be suction while the engine is cold and NO suction when it's at normal operating temperature... There will always be suction through the IACV hole, otherwise the engine will stall.

A good way to think of it is like this:
While the throttle plate is completely closed
IAC is the "main" supply of idle air for the engine.
FIT is "temporary" to allow extra air while the engine is cold.
 

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Discussion Starter · #29 ·
jcast said:
Can you please tell me what controls idling when air conditioning system is turned on on honda cars?
Technically it's the ECU. When turned on, the A/C signal wire 'tells' the ECU to let more air through the IACV...
 

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Discussion Starter · #39 · (Edited)
Sorry I haven't been replying to this lately, here we go...

jcast said:
.Ok, Is there a direct wire that comes from theA/C going directly to the ECU?
Its because when i turn on the A/C, my idle goes down and sometimes kills the engine when idling. It means something does not compensate for idling when i turn on the A/C. If my IACV is ok and is new, maybe the wire from A/C to ECU is cut. Is this possible? Thanks very much Cautela. :)
Yes there is a wire coming from the A/C controls, namely the "A/C signal" (A/C input) wire, look it up in my 'ECU pinouts' write up (check my sig) or better yet look up a diagram that's specific for your car to locate it. Your wire is not cut because if it was, nothing would happen when you turn on the A/C system. The only other thing I can think of is that something is wrong with the ECU... check your voltages/resistances on the A/C, fuel, and ignition systems with a multimeter when you do this to see if something is wrong, also check to make sure the alternator has the proper power output.

EDIT: something just occured to me, the A/C compressor has a clutch which is also ECU controlled... if there is something wrong with THAT it may be possible that the clutch stays engaged continuously, enough that it may stall the engine... just a possibility, someone correct me if I'm wrong.
 

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Discussion Starter · #40 ·
jeremy93LS said:
On my suspected-bad FIT valve, I was able to tighten the springloaded valve 2or3 full turns. I then tested the plunger with a lighter and watched it sloooooooowly expand. It didn't move very much though. Mine never closed as much as the picture indicated. Is that enough to assume that the FIT valve is indeed failing?

I'm having idle problems and the engine will completely bog down and stall when I open the throttle quickly: http://www.superhonda.com/forum/showthread.php?p=3009477#post3009477

Nice write-up, by the way.
jeremy
I read the thread you made about your problem, someone already helped you solve the problem, ignition related ;) .
 

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Discussion Starter · #41 ·
Garyc17 said:
Anyone can help me... I can't seem to locate the plunger (FITV) valve. I have a P73 Type R Manifold and it only has a IACV. And the IACV hole is located behind the throttle body flap in the plenum. I checked the IACV and the filter seems clean. There is a hose that goes to this part under the throttle body put it does not have the plate as mentioned by cautela dude?
This may be due to your ECU needing retuning. Check on that first.
 

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Discussion Starter · #42 ·
96lude said:
Garyc17 said:
What about cases for idle being too high when the car comes to a stop at the lights?
Is this fast idle ?
It's high Idle, check the writeup to diagnose, but start with the idle air screw...
 

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Discussion Starter · #48 ·
klwdallas said:
Followed first part of guide. The white part around the valve was really loose. Tightened it as much as I could.

Idle surge at cold start is gone! Cost $0.

But I still have a little suction on the FITV port in the throttle body intake. Should this be entirely gone? How long should I wait for valve to close?

Kris
A small amount of suction should be ok because it's not going to interfere with the IACV. If it isn't giving you problems then I wouldn't worry about it, my integra has a little suction from the FITV hole after it is warmed up too and it idles fine :tu
 

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Discussion Starter · #55 ·
hema_f117 said:
Cautela said:
Part II

hi

i did clean the FITV and IVCA very well

now the bouncing RPM 1000 to 1500 is coming alwayes
before it was sometimes only


what should i do ?
Do a valve clearance check/adjustment...
 

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Discussion Starter · #58 ·
cowlag said:
I'm stumped... ( 95 honda civic Lx 4 door 1.5 L)

I've tried everything on this guide and can't find anything that works, I even replaced the IAC valve and took apart the FIT twice adjusting it it only turned maybe one full turn it seemed to already be bottomed out.
I held the plunger under a lighter for about a minute and it seemed to work just fine expanding like it should...

the only other thing I hear it could be is the valves/lifters/lashing/rocker arms whatever you call them need to be adjusted... ( you would think the engine light would turn on...)

I am wondering if anyone else has any other ideas I tried to set my idle and it really won't let me, at first it would always go from 1,000 to 2,000 up and down up and down but now it goes from 1,000 to 1,500 just bouncing with maybe a half second pause in between.

Tried checking for codes and nothing showed up maybe I should just take it to the dealer and see what they say? really don't want to have to pay the big bucks but I don't want this reoccurring problem to hurt my engine, I'll hold out for a couple days and see if anyone knows anything else that it might be???
Don't take it to the dealer unless you like to spend unnecessary amounts of money, they'll probably replace a whole system in the engine just to get rid of a simple problem (and charge you the highest price for it). That is unless it is under warranty, which I doubt a '95 model would be...

Take it to someone that knows how to adjust the valve clearance, or if you can do it yourself, it is relatively easy on the d-series engine. If you need the specs you can probably find them on this site. I'd go that route first...
 

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Discussion Starter · #69 ·
If you read the write-up, it suggests performing a valve adjustment, that could be it.

Bleed your brakes, refill properly.

If you cannot do these things on your own, take it to a mechanic. Those are pretty much your only options/
 

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Discussion Starter · #74 ·
I never took the time to become very familiarized with the accord line of engines, so I do not have a good answer for the above questions, I apologize for that... However I can refer you to someone that knows; I suggest "female four", she has appeared to be very knowledgeable on the accord engines in the past, she should be able to help you.
 
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