Idle Adjustment & Emissions Help, includes PCV and Black Box info

[POS carb]

search for "dieseling", u may get some clues about this "idle cut-off solenoid"..

PCV?

The only thing I can think of is a lean mix, causing both idle cycling and higher temps which in turn cause run-on.


HERE IS A CHECK LIST OF THINGS YOU SHOULD TAKE A LOOK AT
ASIDE FROM THE THINGS LISTED IN THE MAIN THREAD
Check for Vacuum leaks
- Intake Manifold Gasket
- Vacuum lines
- Carburetor Gaskets
- PCV Valve
Check your oil system
- Oil / Oil Level
- Oil Filter
Check the coolant system
- Radiator Fluid Level
- Thermostat
- Fans / Thermoswitch
- Waterpump
- Check your engine temperature
- Does the engine heat up to normal operating temp?
- Does the engine overheat?
Check Ignition
- Plugs
- Wires
- Ground Wires ( Battery / thermostat / radiator support )
- Cap / Rotor
- Ignition Timing
Check Fuel
- A/F Mixture
- Float level
- Fuel Filters
Check Idle Speed ( Cold / Warm )
- What is your idle speed when cold in gear and in neutral?
- What is your idle speed when the car has warmed up all
the way and you have driven for 10 mins, in gear and neutral?
Also Check the fuel solenoid at the back of the carb, it could cause idle problems if fit doesn't work.
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PRINT THIS PAGE
THE PRE-PRE CHECK
(1) It's a good practice to be sure there are no vacuum leaks cause a vacuum leak will hinder idle adjustments and will mess up the fuel mixture and delivery.
Some Things That Can Cause Vacuum Leaks
- PCV Valve
- Intake manifold and Carb Gaskets
- Vacuum Lines
- Faulty Thermovalves, check valves, or Solenoids
- Leaky diaphragms
- Leaky O-rings or internal carb passages
(2) Also make sure your float level is set correctly.
(3) Always check oil and radiator/coolant fluid levels before starting the car. This is good in it's own way but for the sake of idle adjusmtent, the themovalves require coolant in order to operete parts on the carb correctly.
Also an overheating car can have idle and driving problems, and a carb not receiving coolant can have winter driving problems.
(4) Another possible problem is a loose booster venturi, click here to find out how to check them. (http://www.3geez.com/forum/showthread.php?t=48568)
I adjust my carb the way listed below. This may not be how the manual/book does it.
Just to let you know I don't have these things on my carburetor:
- Fast Idle
- A/C Idle boost
- Choke
However I'll include adjustment for the A/C idle boost.
I also don't have more then that on my carburetor cause I removed many parts but for the sake of discussion I'll add on parts and show you when I adjust them.
Remember most adjustments to idle speed or ignition timing are made with the car fully warm. The only cold adjustments are the FAST IDLE and CHOKE.
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First I start off by setting the base ignition timing, which is the Ignition timing without vacuum or rpm advance / retard. So you need to disable / disconnect both vacuum advances ; Vacuum lines #2 & #25.
When disabling the vacuum advance you disconnect the vacuum lines to the advance diaphragm... these two vacuum lines need to be sealed so that they do not bleed vacuum and cause a vacuum leak while disconnected.
Next set the ignition timing with a timing light aimed at the flywheel or plate on the torque convertor.
Usually you won't need to disable #25 because all idle adjustments should be made with the car fully warm. When the car is fully warm there is no vacuum running thru #25 to the distributor vacuum advance port.
Also the first idle adjustments should be made with the A/C and Accessories OFF.
With everything off and the car fully warm, prevents the accessories, the choke, and cold start equipment form interfering in the idle adjustment process.
The Prep , If you can't or don't know how to adjust ignition timing then proceed to STEP-THREE. However if ignition is your problem and you choose to skip adjusting ignition, then you'll just be masking your ignition problem with a higher idle.
So:
(1) Set base ignition timing ( Vacuum Advance disabled ) Refer to steps above !
... IMPORTANT. Remember, after you set the base ignition timing you need to reconnect the vacuum advance #2
Connecting #2 before or after adjusting the throttle stop screw will affect how your car will respond when there is a sharp drop in manifold vacuum.
If you connect #2 after adjusting the throttle stop screw then a sudden drop in manifold vacuum wont bother the idle.
If you adjust the throttle stop screw after #2 is reconnected then a drop in manifold vacuum can lower the idle past the throttle stop screw setting; although the idle diaphragm if connected should even out the idle.
#25 can remain disconnected.
(2) Turn out all Idle Diaphragm screws (If you need to temporarily raise the throttle stop screw... For Example if the idle droped way below 800 rpm )
Here Are The Two Scews
... a. A/C idle boost screw
... b. Idle Diaphragm Screw ( Dashpot )
* This will keep these screws from interfering with the throttle stop screw idle adjustment.
Now it's time to adjust the idle speed
(3) Set the Throttle Stop Screw to the Best & Lowest RPM idle speed.
Usually this is about 500 - 800 RPM, but you may need it higher.
Remember it is possible to set the throttle stop too high... too high meaning the throttle plate is open too far causing the carb to come off of the IDLE CIRCUIT. When the carb is off the IDLE CIRCUIT it has a hard time pulling fuel form the idle jet, and it could cause idle problems.
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3a.) Not that you should, but if you need to, now is the time to adjust the fuel mixture and see if it affects idle. I've adjusted the A/F screw on a weber carb so that the idle raises... and back off when the idle stops raising.
3b.) Readjust the Throttle Stop Screw as needed.
3d.) If you haven't already done so now is the time to connect #2 vacuum advance.
4) Turn the Idle diaphragm until you reach a stable rpm... about 1,000 rpm the MAX is 1200 rpm in neutral... adjustment past 1200 is not recommended, and you should look elsewhere to fix your idle issues.
Usually 1000 RPM in gear (automatic) or 900 - 1000 with lights turned on is a good idle speed.
There is a second segment added to the body of the A/C idle boost diaphragm that aids in idle when the car is in gear.
The vacuum port on this segment connects to vacuum line #21
The idle diaphragm adjustment and A/C idle boost is partly to help automatic cars run when in gear and also aide both manual and automatic cars in idling when the headlights and regular interior fans are turned on.
*A/C SHOULD NOT BE ON*
IF YOU HAVE A/C GO TO STEP #5
5) Keep the headlights and fans on and also turn on A/C
Adjust the A/C idle boost to raise the idle speed back up to where the idle speed was prior to the A/C being turned on.
BTW when I say turn on the A/C it should be at full blast.
After the A/C idle boost is set you're all out of adjustment screws... at least ones for idle after the cold start process.






Here is an image, but the quality was junk so I started to type in what I could make out... if anyone has the original image in better quality please scan it in.
http://i23.photobucket.com/albums/b351/Wendy_girl/car%20stuffs/carb005-2xc.gif

[A20A1]

variations in method for idle adjustment



1. What is the right order to set:
Idle control screw, mixture screw, throttle stop screw and fast idle screw
2. Without removing the top hat of the carb can i adjust the float level? Screw it clockwise make it leaner or rich?
3. What parts of the carburetor is responsible for the fuel consumption in normal revolutions or between 800 and 3000? I want the carburetor to help me spend less gas between this rpm.
4. May be this is a stupid question!!! Sorry. When the car is accelerated at 2000 rpm the exhaust pipe throw out less air than when is in minumum rpm 750<800 . Why? Does the engine breath for the exhaust pipe?
Thanks. Martin.
About my car.. Is an honda civic el 1993 (japanese version) 1343cc.


1. I don't think there is an order for it. I always adjusted my idle screw to 1k rpm and go from there. If idle start dropping you can always bump it up with idle screw.
2. The float level is adjusted from the top of the carb. Remove the air cleaner box, and you should see yellow paint, or follow the fuel line to where it connects to the carb. Just be careful, too much adjustment and you can screw up the o-ring that is inside. If that happens, the fuel will start coming from the top around the screw. The best thing is to look at the fuel bowl window and make sure the fuel is in the middle or just a little above.
3. To adjust the idle mixture, which is responsible for up to 3000rpm, you need to remove the carb, remove the plug that covers the idle mixture screw and put it back on the car. There is no other way you will be able to do that.
4. I am not sure about jdm carbed engines, but in the us we had egr system, that moved some of the exhaust gases from the exhaust manifold to intake manifold.


1. Fast idle speed is set whenever the car is cold, other settings will not affect it. The mixture screw should be set once you have a baseline idle set with the throttle stop screw. Hook up a vacuum gauge and adjust the screw until vacuum reaches its highest reading (or engine stops raising rpms if u have no gauge). Now your mix is set. Vacuum leaks will throw your settings out the window.
Set the idle stop screw first to about 500 rpms (engine barely running) then set the idle control screw to around 800 rpms then bump up the throttle stop screw till raises the idle to 800-1000 rpms (or wherever you like it). Your idle is set.
2.the float should be adjusted while the car is running. Remember that raising the float level occurs rapidly, lowering it takes some time (at the rate the engine consumes the fuel). You should have the fuel level smack in the middle of the view window (or just slightly over the center).
3. That's the main responsibility of the idle circuit and the primary jet. I don't think the secondary opens that soon.
4. This could be one of 2 things. A. You interpret the turbulent air coming out of the exhaust at idle as more volume of air than at 2k rpms. This makes no scientific sense really but there is in fact an emissions component in these cars that is solely designed to pump fresh air into the exhaust pipe between exhaust strokes (it actually doesn't pump but runs on exhaust system scavenging effects and it is shut off by the "ecu" after a certain rpm somewhere around 2k like you said... You can hear it operating by removing that odd-shaped black pipe on the drivers side of the air cleaner)


http://www.3geez.com/forum/attachment.php?attachmentid=4543
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For reference here is where the four sources of vacuum are located.
- Filter / Intake Vacuum (Will be higher depending on size of airbox plenum)
- Venturi Vacuum (Strongest Signal @ WOT)
- Throttle Port Vacuum
- Intake Manifold Vacuum (Strongest Signal @ IDLE)
http://www.3geez.com/forum/attachment.php?attachmentid=4542
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Any additional info or corrections please add post below.
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All that worked out... I'm pretty certain you could get a weber carb or a different carb to work with the accord black box.
You would need to drill and make ports in the carb for:
- Venturi vacuum port... the same diameter as #11 about the same point inside the venturi.
- Throttle port vacuum port... again the same diameter as the keihin and in the same place in relation to the throttle plate.
- Vapor Venturi Vacuum port to suck in vapors from the charcoal cannister.
- Manifold vacuum is not a problem.
A few things not needed is the choke opener and the float bowl vent.
Which are Black Box #26 & #8
As for thermovalves.
the two at the back of the intake manifold are still used.
- #18 is plugged
- #17 on both thermovalves are connected to the air cleaner
- #19 is connected from the thermovalve to the black box, there may be more I have to look, but it's no longer a part of the fast idle unloader...
- #25 is cold ignition advance and should still be used
- The themovalve (thermowax valve) on the thermostat housing is not needed so #28 and #17 will not be used from that
A few details that need to be looked into is the obstruction of the metal vacuum lines when using a new carb.
http://www.3geez.com/forum/attachment.php?attachmentid=4487

[dalinxz]

if your engine is idling rough an is having problems make sure you change the pcv valve its only about $4CAD and you can do it yourself I just did mine and it fixed the rough idling and everything.

pcv valve

PCV VALE HELP

http://www.3geez.com/forum/attachment.php?attachmentid=4552
http://www.3geez.com/forum/attachment.php?attachmentid=23

[A20A1]

HIGH IDLE HELP



Sorry For Misspelling "vacuum" in the gifs :)



High Idle Causes are:

1) Sticky throttle cable
2) Sticky throttle component
3) Weak Return Spring
4) Vacuum Leak
5) Fast Idle component
6) Bad Idle Diaphragm / Throttle Controller Adjustment
7) Bad Throttle Stop Screw Adjustment
8) Bad A/C and or idle Boost Diaphragm screw adjustment.


Expansion on # 4)
Two ways a Vacuum leak can increase idle speed:
a) It allows the throttle controller to open the throttle
* Please note in most cases it's not the throttle controllers fault.
The function of the throttle controller is one that uses vacuum
drop to activate.
Though a throttle controller can leak and cause it's own activation,
then throttle controller should be replaced. To test the throttle
controller for leaks directly use a hand vacuum pump and see if
the arm of the throttle controller retracts into the diaphragm and
hold with vacuum applied.

b) It mixes air with a rich fuel mixture and acts as though you have
an open throttle plate. Might include bad float adjustment or
A/F screw adjustment.

Bad Solenoids or Thermovalves can either create a constant
unregulated vacuum leak or block vacuum from reaching it's source
which will leave the connected valve, diaphragm, etc. unable to function.


Here are some helpful threads to look over before you ask any questions:
1) Check for vacuum leaks.
STEP 1 (http://www.3geez.com/forum/showthread.php?t=48569)

2) Check idle Adjustment.
Step 2 (http://www.3geez.com/forum/showthread.php?t=46572)

In each Step (LINK) is a list of other possibilities and/or pre-checks to help ensure that adjustments are made under the right conditions.

Please wait for the animated gif to load, watch and learn.

Vacuum naturally drops as you open the throttle so you don't notice the effects of the throttle controller opening the throttle... however if there is a vacuum leak or a drop in vacuum the throttle controller will open the throttle increasing your engine RPM... it doesn't matter if the leak is intentional or not since most vacuum will all come from the same source, a vacuum leak anywhere effects the entire system.
http://i23.photobucket.com/albums/b351/Wendy_girl/idtc_screw2.gif



Well by the animation you should be able to see how a idle diaphragm screw, set in too much will cause the idle to go up... now say it goes up enough for the spring just to start overpowering what vacuum is available... and does so. Now the throttle opens more... more throttle less vacuum... what happens to the idle? is shoot up... the error has compounded itself.

More in depth animation on the vacuum diaphragm
http://i23.photobucket.com/albums/b351/Wendy_girl/41985184.gif

[A20A1]

Now when you have a vacuum leak or some other carb problem you may decide the simplest solution is to turn up the idle by tightening the throttle stop screw or the vaccum idle boosters/ throttle controller DON'T DO IT!

You don't want to adjust your carb that way because after you fix the vacuum leak or replace the faulty part you have a properly idling carb but with an over adjustment on the throttle controller or stop screw and this is where you now have a high idle problem.




Do you find yourself turning the throttle stop screw or vacuum idler screw higher and higher with not much effect? Have horrible milage? Hot engine?
Wierd out of control idle? Problems starting and idling when cold?
Chances are you turned the screw too far and now are off the Idle Circuit.
The idle circuit is what provides you with fuel to idle when manifold vacuum is high. When manifold vacuum is low, like when you open your throttle plates. The idle circuit no longer provides fuel... no fuel and the car doesn't run.
Now this usually requires a vacuum leak... or else the high setting on the throttle stop screw will push you constantly to 4000+ rpm. The vacuum leak basically stop extra fuel from coming out of the venturies so you really are just gorging on air and running lean. good bye A20



Well in most cases who cares if it's broken or not... to rule something out it must be disabled Completely. So when you go about fixing your odd high idle issues keep in mind you want only one thing touching your throttle linkage.
That is the Throttle Stop Screw.

What does this mean? Disconnect the throttle cable, idle diaphragm screws, and fast idle screw, to keep them from influencing idle.
If you unscrew them they wont increase the idle speed...
You can then bring back components one at a time as you fix them.




For simplicity sake and to stop the idle from doing more then it should.
Set the throttle stop to the lowest best idle speed.

Now Automatics can be set a little higher then Manual cars since they need to remain in gear.

When you toss your car in gear (auto) note how many rpms it drops.
If it's 100 rpms, then add 100 rpms with the throttle stop. Go back inside the car, throw it in gear again, now the idle should be at the lowest setting, and already adjusted to handle the gear.
You don't have to do it this way though. You can forgo compensation with the throttle stop and use the other idle diaphragms to make up the difference. Usually it's better that way anyways.

Nothing below 450 rpm... close to 800 rpm is nice.

[steveko]

Hey new to the site , I think the A20A1 is on the right path with this one from what Ihave experienced with my 1988 LX accord. I found the throttle controler out of spec 1500-1700 rpm per shop manual. Adjust with car normal operating temp vaccum line dissconnected. Also I had too replace a leaky choke opener before doing the throttle controller.Hope this helps.

Steveko.

[A20A1]

*** emissions emission tests testing test pass hc co nox egr failed help smog ***

EMISSIONS TESTING HELP




Methods to help reduce NOX , HC ( Hydrocarbons ) , CO ( Carbon Monoxide )

:KEY:
[B]#) Solution
--- Problem it addresses
-- More Related Solutions

0) Ignition System . make sure it's working properly
--- You could have, High HC from poor ignition

1) Retard ignition timing to give more combustion time
--- You could have, High HC from incomplete combustion

2) Compression , Compression Ratio , Fuel Octane
--- You could have, High HC from poor compression
-- Change Fuel Octane
-- Check Engine Compression

3) A proper Stoichiometric A/F mixture will increase combustion temp, a lean mixture will increase engine temp as the combusted gas mix doesn't absorb combustion heat.
--- You could have, High HC from lean mixture

4) Enrich A/F mixture to decrease engine temp as unburnt AF mix will absorb heat from combustion.
--- You could have, High CO from a rich mixture
-- Rich mixture caused by improper carb adjustment
-- Rich mixture cause by ingestion of fumes from Charcoal Canister
-- Rich mixture cause by restriction Dirty Air Filter
-- Rich mixture cause by restriction due to malfunctioning choke
--- A Richer Mixture may increase HC or CO
--- Too Rich a mixture can melt the Cat

5) EGR
--- NOX reduced by the EGR
--- EGR lowers the combustion temperature



EGR VALVE
There are different vacuum sources used for the EGR CONTROL VALVE inside the black box.
1) Throttle Port Vacuum
2) Manifold Vacuum
3) Venturi Vacuum
They all connect to a big valve body inside the black box.

The EGR VALVE runs off vacuum supplied by VACUUM LINE #16
CLICK HERE: To see the diagram of the black box. (http://www.3geez.com/forum/attachment.php?attachmentid=4543)
CLICK HERE: To see the diagram of the engine. (http://www.3geez.com/forum/attachment.php?attachmentid=4487)


You can also look at the shop manual and test the EGR valve
However the the vacuum diagrams in the shop manual are not
of the US model accord.
SHOP MANUAL (http://www.3geez.com/forum/showthread.php?t=25137)





High NoX is usually directly related to the EGR. Very common on the 4th gens since the EGR ports get clogged very easily. I'm not sure if it will harshly change other readings though. Probably want to hook it up again to be safe.
- Clogged EGR passage

If your high flow cat is a "real" good quality high flow cat, then in most cases I've seen, it should get lower readings than the original cat. If it's just a test pipe or a cheaply made CC, then that might be your cause. Could also be your O2 sensor.
- Catalytic Convertor
- O2 Sensor

If I have trouble passing emissions here in BC, I usually get high octane gas, dump some more octane booster in it, retard the timing, make sure the car is tuned up, and drive the car at least 30 minutes on the freeway or something before going to testing.
- Octane




HERE IS A CHECK LIST OF THINGS YOU SHOULD TAKE A LOOK AT
Check for Vacuum leaks
- Intake Manifold Gasket
- Vacuum lines
- Carburetor Gaskets
- PCV Valve
Check your oil system
- Oil Level
- Oil Filter
- Oil Weight
Check the coolant system
- Radiator Fluid Level
- Thermostat
- Fans / Thermoswitch
- Waterpump
- Check your engine temperature
- Does the engine heat up to normal operating temp?
- Does the engine overheat?
Check Ignition
- Plugs
- Wires
- Ground Wires ( Battery / thermostat / radiator support )
- Cap / Rotor
- Ignition Timing
Check Fuel
- A/F Mixture, also check the screw is still there as in some cases the A/F screw falls out the back of the carb.
- Float level
- Fuel Filters
- Fuel Pump
- Solenoid at rear of Carb
Check Idle Speed ( Cold / Warm )
- What is your idle speed when cold in gear and in neutral?
- What is your idle speed when the car has warmed up all
the way and you have driven for 10 mins; The RPM in gear and neutral?
Emissions System
- O2 Sensor
- EGR Valve
- Catalytic Convertor

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[steveko]

Does the AC idle boost work when the lights are on and not the AC?

[2oodoor]

why? any particular issues you are having?
At one time I had the manual printed out and studied the oem carb functions, sensors, black box.. the whole deal , but when I switched to weber I threw those away. I remember some of it, but have no use for it other than helping others with oem carb issues.. I got it in the betamax vcr troubleshooting part of the bwain. lol
Just look at the online manual here and follow the schematics. I think if it is like most cars there is a solenoid that kicks on with the compressor and then actuates a electrical vacuum valve for the ac idle stepper.
Great thread you bumped here.

[steveko]

I was just trying too find out why my idle drops so much when the lights are on.Below the idle setting. Sorry,wasn't trying too bump this thread.

[russiankid]

I was just trying too find out why my idle drops so much when the lights are on.Below the idle setting.

I don't think so. It drops because of the current draw from the alternator. I know the EFI motors have an extra wire on the alt to tell the ECU to raise the idle when to much current is being drawn.

[A20A1]

I was just trying too find out why my idle drops so much when the lights are on.Below the idle setting. Sorry,wasn't trying too bump this thread.

You should turn your lights on then adjust the idle screw on float bowl side of the carb as well as the throttle linkage side of the carb till your idle smooths out, only adjust it when the car is fully warm... you can tell if your A/C Idle boost screw is making a difference or not, pretty quickly by playing with the a/c after you make your adjustment. The screw on the throttle side has a greater range of adjustment so don't turn it too much.

After you're done turn the lights off and then see if you're idle stays the same, drops, or raises... if it starts to go too high like into the 1200+ range then you should back the idle screw on the throttle side out some to lower the idle. It could mean you need to find a different solution to your idle problem, like power drain... possibly swapping where you hook your ground wire too or cleaning battery terminals can help in some cases.

*Those rpm values are pretty arbitrary so don't follow them too closely.

[Thaguardian]

ok thats a good diagram but let me ask this question could this be the problem of why my car idles high and i have to keep hitting the gas pedel to have it release the choke

[87DXACCORD]

ok thats a good diagram but let me ask this question could this be the problem of why my car idles high and i have to keep hitting the gas pedel to have it release the choke

i'm also having the same problem idles high like around 2500 to 3000rpm when warming up. would cleaning the choke real good stop the problem or is a vaccum leak causing the problem? I'm new to carbs so i;m not sure how that whole system works

[russiankid]

Thats how they work. Tapping the gas moves a latch which has 3 notches on it, 2500rpm, 2000rpm, and 1500rpm.

[zebratow]

Hi, I'm new here, so I'm not sure I'm asking this question correctly or in the proper place.

Problem: my 88 Accord (carb)won't adjust the idle speed when the a/c system cycles on/off. Whether the a/c system is running or not, the idle speed remains "slow" or unboosted as if the a/c system were not on & running.

What I know so far:
(1) The a/c idle boost vacuum diaphragm works correctly and there are no leaks in the associated vacuum hoses.

(2) The Idle Boost Vacuum solenoid seems to be working correctly--if I unplug the electrical plug to the solenoid from the harness and run a jumper wire from the battery to the solenoid it will dictate fast idle when it does NOT receive 12v, and will dictate slow idle when it DOES receive 12v.

(3) When I check the voltage coming to the solenoid in the wiring harness plug, I get about 14 volts when a/c system is cycled off, and about 10 volts when the a/c system is on & running and the a/c clutch is cycled on. As a result... the solenoid is always getting at least some current (10 or more volts), therefore it always dictates slow/unboosted idle (as when a/c clutch is cycled off).

It seems to me that something is allowing about 10 volts to come to the idle boost vacuum solenoid when the a/c clutch is cycled on it when in fact no voltage should be going to the solenoid at that time.

I don't know where to go from here. Any help will certainly be appreciated.

Thanks,
Paul

[james9120]

Lol yeah that's how chokes work...

[rvd]

im gettin there

[rvd]

I bought this car like this, and I know how the lines are supposed to run, but I just dont know why, Im assuming that the auto choke stopped working?? can I just clean it, run the vacuum lines correctly and try it? Thanks, Im new to carbs this is my first. Im thinking this is the reason my car is idling like crap.....

http://i69.photobucket.com/albums/i64/robs90tsi/IMAG0018.jpg

[Xaisk]

yeah I would bet that has something to do with it for sure. Look up under your hood. You should have a VECI label explaining what everything should be adjusted too along with a diagram for ALL of the vacuum hoses in the car. Its a little hard to follow the diagram because its small, but it will help alot.

[rvd]

I know how they are supposed to run, should I just reinstall them and hope it wasnt removed for a reason?? Thats the throttle actuator right?? what exactly does that do, I know how it works but I just dont know what it does sorry if that sounds dumb...

[Xaisk]

That is the choke. That piece CAN go bad but I dont think the piece would be bad. Just plug the missing hose in and see if there is an improvement.

We have a guide in our how-to section that has a link to a manual. This manual will tell you how to test every little solenoid in the car if it comes to that.

[Greenplus]

Does anyone know how to lean out the carb a little. The car runs really smooth but i have an elevated CO level. I'm scratching my head looking for the mixture screw. Thanks

[Buzo]

Does anyone know how to lean out the carb a little. The car runs really smooth but i have an elevated CO level. I'm scratching my head looking for the mixture screw. Thanks

You didn't give details of your car's model year. But if it has al lot of hoses and valves under the hood, then it automatically controls the air/fuel mixture.

The mixture screw is located in the back of the carb but its access is blocked off from factory to avoid us to move it. You'll need to remove your carb from the car to open the blocked passage.

Better fix whatever may be wrong with your automatic emissions control by following the steps in this post.

[Greenplus]

Thanks for the info. Its an 89 lx


You didn't give details of your car's model year. But if it has al lot of hoses and valves under the hood, then it automatically controls the air/fuel mixture.

The mixture screw is located in the back of the carb but its access is blocked off from factory to avoid us to move it. You'll need to remove your carb from the car to open the blocked passage.

Better fix whatever may be wrong with your automatic emissions control by following the steps in this post.

[Dr_Snooz]

You don't give a lot of extra information. The missing hose could cause a vacuum leak, which would definitely make it idle like poo. Start by blocking it off to see if that improves it.

You mention high CO which sounds like you have recently had a state-mandated emissions inspection and failed. If that is the case, what state? If you have high CO while testing on a dyno at 15 or 25 mph, then don't bother with the idle mixture. It only controls the mixture at idle. As soon as you get going, it stops doing anything. High CO can be caused by a number of things, including a dirty carb. I would start with a tank of premium gas and a bottle of injector cleaner like Techron or the like. You can also buy carb cleaner in a spray can. Other potential causes include: dirty air filter, sticky choke, malfunctioning PCV, bad charcoal canister or a misadjusted carb (probably needing a complete rebuild). Good luck and keep us posted.

[POS carb]

why am I credited with this writeup? This was all Mike's work..........

[Hennessy90032]

My Car Idles At 2,000 - 3,000 Rpm And Wont Go Down.. Some times it idles Ok But It Has A Mind Of Its own... Is It The Carb Or Distributor Or ??? Any Advise...

[A20A1]

When does it occur the most? When warming up or after the car is fully warm?

[JDAccord88]

mine has the same idle problem (2,000-3,000 rpms) sometimes right when i start it up and even if i have driven it all day. It just varies. Sometimes it wont act up at all.

[Dr_Snooz]

Check your accelerator pedal linkage and the condition of the cable. Make sure the cable moves easily and is not binding.

[huntersdl]

Ok idle issue here too.. stays around 2k even when warmed up. SPent hours last night pulling diagrams and reading. Reading this post something dawned on me and i would like to ask a question. I replaced the valve cover gasket but JUST remembered i didnt put the ground wire on the most right (looking towards the drivers seat from the outside) valve cover grommet. Could not putting this ground wire on cause my high idle?

[huntersdl]

anyone have pics or specifics where to find thermovalve A and B? I think i can replace both cheaper than a diagnostic from a pro mechanic for my high 2000 rpm idle at all times. Choke is fine - stays open..... when hot... im not getting vacuum in #19 but i am slight in #18 on the unloader. According to the manual it says to check thermovalve B but everyone keeps saying A is bad... ,What gives?

[g.frost]

I wrote about the high idle unloader circuit here:

http://www.3geez.com/forum/carb-tech/97849-high-idle-2500rpm-wont-come-down.html#post1148126

...BUT download the manual for your exact model! as I think some may be different here (ie thermovalve A vs B)
Both A and B are back under the carb. There is a location diagram also in the manual. (Mine is CA 88 DX manual trans & uses thermovalve A) 18 & 19 are always for the high idle unloader; 18 drops 2000rpm, 19 drops 1500rpm high idle.

If you are getting weak vac on line 18, you could still have a leak in the choke. Just not bad enough (yet) to keep the choke from fully opening. (That's how mine failed) Really best to have a vac gauge/pump in your toolbox. It will save you buying and replacing parts you don't need. Just unplug 18 from the carb and pump the line down to see if your idle drops. If so, the problem is likely choke opener vac leak.

[86 Accordlife]

Ok guys my 86 accord idles perfect when it's cold but as soon as it gets warm and the choke plate fully opens it sputters and dies also pulled the plugs and all were pretty black and cylinder 4 was white any tips?

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