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Troubleshooting Idle Problems

300K views 106 replies 51 participants last post by  rgb17 
#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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#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...
 
#56 ·
Tried everything

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???
 
#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...
 
#59 ·
alright I need the specs please

if you can find the specs that would be very much appreciated, I'm going to try adjusting the idle even though i'm not sure if it will adjust the same way

and then I will try checking the valve clearance to make sure it is within specs (when I find the specs that is), thank you!
 
#63 ·
i have a 98 ls integra. I am having the same problems that everyone is talking about in this thread. erratic idle, sometimes pegged at 2000-2500, sometimes fluctuating between 400-700. also, i have no part throttle. unless the pedal is at least 3/4 the way to the floor, it sputters really badly and is completely undriveable. then once i floor it it surges and powers out of it like it was bottlenecked. if i floor it the whole time it never hesitates. only with part throttle. i just took a look at the throttle body, and I do not have a fit valve. there are two open-ended pipes that are underneath the throttle body that have nothing hooked up to them, but i did not feel a vacuum on either one. (and while checking them i electrocuted myself somehow... dont know how... maybe on the distributer?...makes me wonder if there is a voltage issue) and looking inside the throttle body, there is only the one hole for the iacv. no hole for the fit. in the haynes manual for my car, it says the fitv is just to the right of the head breather. i dont see anything there. i disconnected the map sensor to see if there was a change, and the car immediately died, so i can assume that is fine. there is another sensor directly on top of the intake manifold that i'm not sure about. it is not labeled in the haynes, and it did not effect the idle at all when disconnected. and the car is throwing a system rich cel as well. my next step is to check the iacv. should my car have a fitv? i just swapped a b20b in, but the original b18b im is still on. i never had this problem before the new motor was installed this week, so it seems logical that they did something wrong in the install. whats the next step if the iacv is good?
 
#64 ·
my prob

OK i just bought my 97 accord witha h22 swap in it. when i got the car the girli bought it from said that it had a prob with one of the injectors. the injectors are fine. when i started the car i had to keep giving it gas to keep it running. but once it warmed up it ran fine for i lil bit. the other day my car would start and then it would rev ral high and go back down. I looked on my IM and there was some kind of sensor that was lose and sucking air. I bolted it back on and it fied the rev prob but now I start it and it wants to die and some times it idels fine. then i give it gas and it wants to die and then picks right bac up. what could it be
 
#65 ·
OK i just bought my 97 accord witha h22 swap in it. when i got the car the girli bought it from said that it had a prob with one of the injectors. the injectors are fine. when i started the car i had to keep giving it gas to keep it running. but once it warmed up it ran fine for i lil bit. the other day my car would start and then it would rev ral high and go back down. I looked on my IM and there was some kind of sensor that was lose and sucking air. I bolted it back on and it fied the rev prob but now I start it and it wants to die and some times it idels fine. then i give it gas and it wants to die and then picks right bac up. what could it be
Clean throttle body/intake manifold, see where that gets you.
 
#66 ·
Howdy,

I have a 1994 Honda Civic EX with a D15B VTEC engine and it lopes when it idles and when I put my hand over the throttle body it doesn't stall, it just keeps running so I think it has a vacuum leak somewhere but I just can't find it and it sucks ALOT of air through the IACV hole but I have changed the IACV but it still does it. It even does it when he IACV is disconnected but not as bad. I can't take it to a dealer cause it would be a fortune to fix it.Can anybody please help me? It gets tiresome sitting at a complete stop pulling out and it jumping all over the place!!!! Thank You here is a pic of my Honda.
 

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#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/
 
#70 ·
Idle Question

So I went through the steps here this weekend, FITV is definitely not getting out of the way and results in a jumping idle from 900-1600 or so and sucks the entire time.

So I know my one problem, and am waiting on getting a new FITV valve, thanks for the excellent write up.

My second problem is that the car has taken to just randomly dieing as you are driving down the road. No check engine light has come on. It has died when running at 3000 RPM and at 4000RPM. Sometimes it restarts on compression other times I have to wait 5 minutes then the thing starts fine. Are my problems related, or thoughts, theories, wild guesses? :bash

All help much appreciated.

1991 Acura Integra - 4 door commuter POS
 
#73 ·
IAVC or FIV

I believe the IAVC and the FIV holes inside of the throttle body are different on 89 Accord which is what I’m working on. When I apply my finger on the top hole, vacuum pulls through the FIV. I need help from someone to confirm that this is correct on the 89 Accord. This parts cost to much money for me to just take guess. Thanks
 
#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.
 
#77 · (Edited)
alright, when i unplugged the IACV it stated to make like heart beating noise, my idle was a 1500 rpm, while it was doing this the needle was moving a little, probably like in between the 1500 line and the 1600 line, maybe not even that much, but as i adjusted the idle screw it wouldn't go right at all, so as i turned it to the left the noise got louder( the heart started beating more) <thats the best way i can describe it.. so i turned it back to where it was when i started, plugged the iacv plug back in but now its doing the heart beating thing not very very bad but its doing it, I reset my ecu, and it stopped but the idle is stil 1500. After the car gets warmed up it doesn't stay at 1500 it will go to about 2000 then fall down to 1000 then back to 2000 then it will go to about 1500 and bobble between 1400 and 1700 and then it goes back to going from 1000 to 2000 again and it just continues to do that. Also my CEL is on throwing 9 code CYP: Cylinder Position Sensor, its inside the distributor, so i bought a brand new distributor from honda, well that didnt fix a thing. Im still getting the code for CYP sensor, and the idle is still crazy. and suggestions
 
#79 ·
alright, when i unplugged the IACV it stated to make like heart beating noise, my idle was a 1500 rpm, while it was doing this the needle was moving a little, probably like in between the 1500 line and the 1600 line, maybe not even that much, but as i adjusted the idle screw it wouldn't go right at all, so as i turned it to the left the noise got louder( the heart started beating more) <thats the best way i can describe it.. so i turned it back to where it was when i started, plugged the iacv plug back in but now its doing the heart beating thing not very very bad but its doing it, I reset my ecu, and it stopped but the idle is stil 1500. After the car gets warmed up it doesn't stay at 1500 it will go to about 2000 then fall down to 1000 then back to 2000 then it will go to about 1500 and bobble between 1400 and 1700 and then it goes back to going from 1000 to 2000 again and it just continues to do that. Also my CEL is on throwing 9 code CYP: Cylinder Position Sensor, its inside the distributor, so i bought a brand new distributor from honda, well that didnt fix a thing. Im still getting the code for CYP sensor, and the idle is still crazy. and suggestions
Sounds like a timing issue... the very first thing you should've done before buying a new distributor is check the timing. Get a timing light and check to make sure the timing is right. Then this procedure does not work if you have CELs! (as stated at the beginning), must get rid of that problem first.
 
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