So i have owned this ae86 for 3 years, i impoted it from Japan with a 4age 20v blacktop swapped. The engine is running a bit rich around 11:1 air fuel ratio, and idles a little high at 1500, i checked out everything ( vacuum leak, o2 sensor, etc). Now i found that the throttle body are not balanced, one cylinder is sucking more air than the other three, so i tried to balance the TB by a carburetor balancer following the blacktop manual, but the car is still running high idle, air fuel ratio went better around 12. I am not sure whether i did correct steps for the TB balancing or not, because some parts of the words in the manual are blackened because of the scanning ( last several letters of every line). Could anyone help me out with how to properly balance the TB on blacktop or provide any suggestions? Do i need to reset the TPS after balancing? ( Could TPS even be adjusted on blacktop?) Please forgive my English, i appreciate for any help, wish to get it back on road soon.

How far out of balance were they?
The balance isn't going to have anything to do with the ITB balance though. Balance would make some cyls run richer and some leaner but the O2 would still average them out.

Fortunately you have a BGB though. There are giant sections devoted to diagnostics and troubleshooting. That is where I would start. It will guide you better than just about anyone can.
For the rich AFRs you will want to be looking around the circuits of the O2 sensor, MAP sensor and coolant temp sensors.
For the high idle, it's almost guarenteed you have an intake leak somewhere. Now if someone had tampered with the ITBs before you it may be possible they adjusted the idle up but make sure you eliminate any possibility of intake leaks and other issues before you try to change the idle via the ITBs.
The ISC is another place to look for leaks and or malfunctions.

There are two procedures to PROPERLY set ITB assemblies...

You must set the linkages to operate simultaneously... as well as getting them balanced. I have a sneaky suspicion that one or more of your ITB units is not correctly set - mechanical linkage, or possible throttle stop

oldeskewltoy wrote:There are two procedures to PROPERLY set ITB assemblies...

You must set the linkages to operate simultaneously... as well as getting them balanced. I have a sneaky suspicion that one or more of your ITB units is not correctly set - mechanical linkage, or possible throttle stop

Thank you oldeskewltoy, the throttle stop doesnt touch the supporting pole under it while idling, so i assume it should be fine, but i have taken off the TB before, and didnt do anything with the mechanical linkage after i installed it back on. Should i adjust the mechanical linkage? ( they look like work simultaneous ). I also noticed after i balanced the four cylinders to same air intake amount, one or two of them will increase or reduce the air intake amount by themselves, it makes me confused. Do you know where i can see the two procedures of balancing the ITB?

yoshimitsuspeed wrote:How far out of balance were they?
The balance isn't going to have anything to do with the ITB balance though. Balance would make some cyls run richer and some leaner but the O2 would still average them out.

Fortunately you have a BGB though. There are giant sections devoted to diagnostics and troubleshooting. That is where I would start. It will guide you better than just about anyone can.
For the rich AFRs you will want to be looking around the circuits of the O2 sensor, MAP sensor and coolant temp sensors.
For the high idle, it's almost guarenteed you have an intake leak somewhere. Now if someone had tampered with the ITBs before you it may be possible they adjusted the idle up but make sure you eliminate any possibility of intake leaks and other issues before you try to change the idle via the ITBs.
The ISC is another place to look for leaks and or malfunctions.

Thank you yoshimitsuspeed! The car is running a HKS ECU and an AFR gauge, so the O2 sensor is an expensive wide band sensor from Denso, i just replaced it with a new one several months ago because i have read many posts say that the O2 sensor has the most effect on the AFR. But the car still run rich with the new one on, then i simply tested the MAP sensor with a voltmeter, it shows in normal range. For the coolant temperature sensor, i havent checked that before since it is hidden deeply back into the firewall, hard to reach. But my water temperature gauge shows normal readings, so should i assume the Coolant Temp Sensor is fine?

The Japanese replaced the original ISC with a RX7 one, i replaced the old one with a newer RX7 ISC, it was working fine. Yesterday, after i balanced the ITB, the car idled around 1500, i can feel it is not sucking any air thru the ISC, is that normal? The car would still run if i block the ISC, should the car stall if i block the ISC?

Good god man you gotta tell us about massive non stock changes have been made like a non stock ECU. That is huge.
Unfortunately I don't know anything about the HKS ECU but if it has the ability to monitor a wideband something must be very wrong for it to not work. If it has always done this then it may just be a bad tune.
If it started doing this then you need to figure out what has changed.

It should not idle or barely idle with no air passing through the ISC. You either have an intake leak, the ITBs are horribly out of adjustment or something else is wrong like the throttle or something else holding the plates open, or something like that.
Make sure the dashpot under the ITBs is hooked to the proper vacuum source otherwise it will not suck the piston in and will keep the idle high. Make sure it's adjusted right so when vacuum actuates it the pin sucks in far enough for the throttles to rest on the hard stop.
As OST said make sure all the throttle plates are adjusted properly.

The first thing would be to check that the ecu can read a wideband signal.
If it can't then you would be best off fitting a stock narrowband sensor and reading the AFR with your Denso through the wideband sensor already fitted.
Narrowband simulation from the wideband is also an option.

yoshimitsuspeed wrote:Good god man you gotta tell us about massive non stock changes have been made like a non stock ECU. That is huge.
Unfortunately I don't know anything about the HKS ECU but if it has the ability to monitor a wideband something must be very wrong for it to not work. If it has always done this then it may just be a bad tune.
If it started doing this then you need to figure out what has changed.

It should not idle or barely idle with no air passing through the ISC. You either have an intake leak, the ITBs are horribly out of adjustment or something else is wrong like the throttle or something else holding the plates open, or something like that.
Make sure the dashpot under the ITBs is hooked to the proper vacuum source otherwise it will not suck the piston in and will keep the idle high. Make sure it's adjusted right so when vacuum actuates it the pin sucks in far enough for the throttles to rest on the hard stop.
As OST said make sure all the throttle plates are adjusted properly.

Thank you very much, i apologize for not clarifying the mods. I will reset the TB linkage since i havent adjusted it after i put it back on. I was checking the throttle stop to make sure it donest hold the plates crack open, the little bolt doesnt touch the piston under it while idling, and the vacuum line is hooked correctly. I have been searching vacuum leak without any results for long time, it really frustrates me a lot. I wish there is a vacuum leak somewhere, so the problem becomes clearer. The car was running good so i guess not the problem from tuning. Yesterday i tried to screw the four TB bypass screws all the way back in as it before, the idle set at 1000 rpm, better than if i adjust them to suck in same amount of air (idles at 1500), but it still run rich. With the four bypass screes all the way in, the No.1 cylinder sucks in the most air at 5 kg/h, No.2 and No.3 are around 3 kg/h, the No.4 cylinder is around 2 kg/h. So i guess the TB is all messed up, i will adjust the linkage and balance it again with my weber carburetor balancer, and see if its better.

totta crolla wrote:The first thing would be to check that the ecu can read a wideband signal.
If it can't then you would be best off fitting a stock narrowband sensor and reading the AFR with your Denso through the wideband sensor already fitted.
Narrowband simulation from the wideband is also an option.

Thank you Totta Crolla, the car was running good around 13, 14 AFR before with a wideband sensor, should i say the ECU could read the signal then? I would like to make sure whether the ECU can read the wideband sensor or not, do you know how to check it?

billda wrote: With the four bypass screes all the way in, the No.1 cylinder sucks in the most air at 5 kg/h, No.2 and No.3 are around 3 kg/h, the No.4 cylinder is around 2 kg/h. So i guess the TB is all messed up, i will adjust the linkage and balance it again with my weber carburetor balancer, and see if its better.

Yes... a 50%+ difference is clear sign of need for adjustment - check that each throttle plate actually closes the passage

Also... with any(ALL) aftermarket management, the tune is only as good as the tuner. With you running so rich, I'd begin looking at the fuel side of things, look 1st at the injector parameters (does the ECU know the injectors being used?) You can take screen shots of your tuning tables and we might be able to assist.

oldeskewltoy wrote:

billda wrote: With the four bypass screes all the way in, the No.1 cylinder sucks in the most air at 5 kg/h, No.2 and No.3 are around 3 kg/h, the No.4 cylinder is around 2 kg/h. So i guess the TB is all messed up, i will adjust the linkage and balance it again with my weber carburetor balancer, and see if its better.

Yes... a 50%+ difference is clear sign of need for adjustment - check that each throttle plate actually closes the passage

Also... with any(ALL) aftermarket management, the tune is only as good as the tuner. With you running so rich, I'd begin looking at the fuel side of things, look 1st at the injector parameters (does the ECU know the injectors being used?) You can take screen shots of your tuning tables and we might be able to assist.

Unfortunately, it says that the HKS ECUs can only be tuned by dealers, so i can do nothing with the HKS ECU, it came with the car from Japan since i got the car.I sent all of the injectors for cleaning and testing several months ago, the result says they are all good without any leaking. I have also changed new ignition coils 1 year ago, and new spark plugs months ago.

oldeskewltoy wrote:

billda wrote: With the four bypass screes all the way in, the No.1 cylinder sucks in the most air at 5 kg/h, No.2 and No.3 are around 3 kg/h, the No.4 cylinder is around 2 kg/h. So i guess the TB is all messed up, i will adjust the linkage and balance it again with my weber carburetor balancer, and see if its better.

Yes... a 50%+ difference is clear sign of need for adjustment - check that each throttle plate actually closes the passage

Also... with any(ALL) aftermarket management, the tune is only as good as the tuner. With you running so rich, I'd begin looking at the fuel side of things, look 1st at the injector parameters (does the ECU know the injectors being used?) You can take screen shots of your tuning tables and we might be able to assist.

I was thinking to check the TPS, if it is not in the specs according to manual, can it be adjusted?

billda wrote:
Unfortunately, it says that the HKS ECUs can only be tuned by dealers, so i can do nothing with the HKS ECU, it came with the car from Japan since i got the car

Time to dump that ECU and find something that you can actually tune on...

Where are you??

Are there any shops in your area that have a dyno and do tuning? Is there more than one shop?? Take a few days and check out the shop, ask to watch them while they tune. Find out what they are most comfortable tuning. Once you find a shop you trust, shop for an ECU /management system, that shop has familiarity in tuning.

There is no evidence to suggest that the ECU is not working correctly, or
that it is in need of adjustment. Chances are it is simply reacting to the
inputs it is receiving. Where is the WBO2 sensor located ? In one of the
header tubes or after the collector ?

The fact that the ISCV does not seem to be working could be an ECU problem,
or a wiring problem, or an ISCV problem, or a vacuum tube problem. But
the valve is most likely a simple 2-wire PWM solenoid, so it should be easy
enough to test. 12V across the pins and it will be open wide. No voltage and
it will be fully closed. The normal action for an ISCV is to open and raise the
idle to the required rpm. However, if the rpm is already above the required
target, then the ISCV will most likely try and bring the idle down by closing.
Some guessing here as I don't know what lives inside an HKS ECU

Once you have all four throttles fully closed and sitting on their throttlestop
screws, adjust the linkages so that they are all opening at exactly the same
time. Then you can fine tune with the by-pass screws to get equal airflow.

You will need to check the setting of the TPS, as any time you change the
position of the throttlestop screw on the #1 ITB you will also change the
TPS setting. Good luck

Cheers... jondee86

Thank you guys for this much info. I am in Columbus Ohio, i have called several tuner shops here and asked if they can tune a HKS ECU on a JDM car, unfortunately they cant.
The O2 sensor is located under the car and below the pasanger seat, so it is after the exhaust collector. I can hear the ISCV sucking air when the car is just started, the rpm raises a little then drops down, but its not sucking air while idling, Thank you Jondee86 for the procedures of testing the iscv, i have read your previous posts about cleaning and testing iscv, and cleaned and tested mine several months ago. I remember i tried to block the iscv after that while the car was runing, i could feel the car was breathing very hard, and almost stalled. Now i think that as you said, the TB needs adjustment so the TPS,too much air is sucked from TB and even the ISCV closes itself, it wont bring the idle down? Would this also cause rich AFR because of the messy TB setting?

Also, for the HKS ECU, it is using another map sensor comes with it and the original map sensor is also hooked, but the original map sensor doesnt have a vaccum line on it, i havent done anything to these two map sensors since the car came like that and ran good, do i need to find a vaccum route for the original map sensor? I really appreciate for everyones help.

If the factory MAP sensor did not have a hose on it when you got
the car, leave it that way. The ECU might use it for barometric
correction, Changing things when you don't know what they do is
the recipe for a big headache !!

It is usual for the ISCV to provide extra air to assist starting, and
then taper back once the engine is running. The factory design for
idle air control requires that ALL idle air passes thru the ISCV. The
OEM ECU has a target rpm vs temp table, and adjusts the ISCV to
bring the rpm on target. I would expect the HKS ECU to do the same.

This control strategy reqires that all four throttles be completely
closed when on the stops. The throttle by-pass screws are factory
adjusted and set to balance the throttles. They are not something
that needs adjusting as part of an engine "tune-up", and should not
be used to try and cure other problems.

Without digging up the BT manual, I would imagine it says that
if you have to re-balance the throttles, you should screw all the
by-pass screws all the way closed, and then open the screws on the
three lower flowing throttles to match the highest flowing throttle.
This only being done after all four throttles have been adjusted to
close completely.

While I don't have a 20V, I did have to go thru this procedure when
setting up ITB's on my DIY intake manifold. It proved to be virtually
impossible to do it with the intake installed on the engine, so I
pulled the manifold out and set up the ITB's on the bench. That way
I could hold the whole thing up to the light and see which butterfly
was opening first, and check that the operating arm hit the stop
at exactly the same time as the butterfly touched the bore (zero
clearance on the stop).

Does the engine only run rich at idle ? What about at cruise and WOT ?

Cheers... jondee86

Thank you Jondee86!! The car came with all four throttle by-pass screws screwed all the way in, i used a carburetor balancer to see if each cylinder was sucking the same amount of air, but with the four by-pass screws all the way in, the No.1 cylinder is 5kg/h, No.2 and No.3 are around 3kg/h, and No.4 is around 4kg/h. So does this mean that the by-pass screws were already messed since i got the car?

So from what you said, it seems very helpful and getting things much clearer, but i am still confused with several things.

1. When you say the throttle body completely closed, does that mean if i put my carburetor balancer on each throttle at idle, i should get a "0kg/h" reading for every throttle? Since all air for idling should be coming from the ISCV? Also, Is the fully closed TB achieved from adjusting the linkages that connects the four throttles.

2. When the TB is fully closed, should the Throttle Body Stop screw sit on the pin? ( Mine is not sitting on the pin while idling, so the butterflies are open, not fully closed i guess? )

3. After i set the TB fully closed, then adjust the by-pass screws to achieve the balance, would the adjustment of by-pass screws opens the butterflies to let more air in by following the steps in the 20v manual? In this way, the TB is not fully closed again? Otherwise, does the by-pass screws allow more air in from another path?

4. From the 20v manual, it says to use feeler gauge to adjust the the linkage, do you think that to pull out the manifold is easier than using feeler gauge?

The engine's AFR seems normal at cruise, but rich at idle, and the stinky smell makes feel sick if i stay in the garage for longer than 10 mins.

Thank you so much for your help.

Hmmm.... I think if I run thru this from first principles, it might help
to clear up any misunderstanding...

Throttle Bypass Screws
These operate quite independently of any other adjustment to the ITB
and when opened, allow a tiny amount of air to bypass the throttle plate.
They are a "trim" to compensate for any small differences between the
amount of air leakage around the fully closed throttle plate on each ITB.
They are not intended to be used to compensate for differences due
to the incorrect adjustment of the throttle stop screw or linkages.

Throttle Stop Screws
Each ITB is provided with a adjustable stop screw on which the throttle
arm comes to rest. Essentially, the throttle plate should come into contact
with the throttle bore at exactly the same time as the throttle arm hits
the stop (zero clearance). This makes sure that the throttle plate is
completely closed, but prevents it from impacting on the throttle bore
and cutting a groove. The throttle stop clearance has to be checked, and
reset if necessary, before any other adjustments are carried out.

Linkage Opening Clearance
To ensure that all four throttle plate open at near enough the same time,
the opening side clearance is set to 0.03mm. Thus the #1 and #4 throttles
open a tiny fraction later than the #2 and #3 throttles. The Return side
clearance in not critical and is set much larger, as each throttle has its
own return spring, and does not rely on the linkage to "push" it closed.

So, on to your questions...

1. It is possible that if the throttle stop settings of linkage adjustments
were out, someone may have messed with the bypass screws to try and fix
the problem. If you got a wide variation in flow with all the bypass screws
all the way in, then I would say that is what happened.

1a. "Fully closed" is set by the throttle stop screws on each ITB. After that,
not being fully closed is caused by the incorrect setting of the linkage
opening clearances. If you could remove the linkages to eliminate them as
a variable, then set the throttle stops (bypass screws all the way in) you
should have near enough to zero flow. But because nothing is perfect, there
will be some small degree of leakage around the closed throttle plates, and
once you have used the bypass screws to balance for equal leakage thru each
throttle, you might measure some very low flow rate on each.

2. Yes.

3. Refer explanation above.

4. I will leave it to you to decide It is an awkward job just seeing what
you are trying to adjust, and with less that four hands to hold a light, feeler
gauge, hex key, tiny spanner and rotate the linkage to a point where you can
get at the adjusting screws.... I found it easier to do on the bench.

4a. I'd say that it is probably rich at idle because the extra air leaking thru
the throttles is dropping the manifold vacuum and the ECU is adding extra
fuel. I found that once I got my throttles adjusted correctly, my ISCV had to
open quite a few more clicks. The fact that your AFR's are normal while
driving says that your ECU is most likely working OK. BTW, you shouldn't
be working in the garage with the engine running and the door closed !!!

Cheers... jondee86

Thank you so much for your help, it makes things much much clearer now! I will pull the TB out to do the work. I think i messed up the names with throttle stop screws and throttle opener screw, i noticed that the linkage above the throttle opener does not sit on the throttle opener bolt at idle, i think this would also cause the butterflies open, right? Should it sit on the throttle opener bolt at idle? Also, with the engine off, i could turn the accelerator cable bracket backward, this would close the butterflyies a little more. Should i adjust the throttle opener screw to fix this?

The throttle opener holds the throttles slightly open when the engine is off.
This apparently helps the engine to start, although many people remove and
discard this item without any problems. When the engine fires, vacuum is
applied to the throttle opener servo, and the rod retracts until it is clear of
the throttle arm for as long as the engine is running.

The FSM says to apply vacuum while adjusting the throttles... this is to make
sure that the throttle opener is retracted. Sounds like yours is working OK.
If the throttle opener is being a nuisance while you are trying to adjust the
throttles, just remove it temporarily until you are ready to put the throttles
back on the engine.

When the engine is running, if all the throttle arms are resting on their
throttle stops, you should be able to press down on the arms with your
finger, and NOT hear any change in engine revs. If you do hear a change in
revs, then something is out of adjustment.

Cheers... jondee86

When the engine is running, if i would be able to press down on the arms with my fingers, would that mean the throttles are slightly open? Why would the engine revs have no change? Shouldnt the pressing down closes the throttles and let almost zero air flow thru the throttles? Also, with all the throttle arms resting on their theottle stops, how would this let me press down on the arms? Isn't it already the end of the throttle arms? Thank you Jondee86!

By the way, are you in the states Jondee86?

When the engine is running, if all the throttle arms are resting on their
throttle stops, you should be able to press down on the arms with your
finger, and NOT hear any change in engine revs. If you do hear a change in
revs, then something is out of adjustment.

You are correct. If all the arms are resting on the stops and you press down, there
will be no movement, and there will be no change in revs. But it is not easy to see
if the arms are on the stops, so pressing down and listening is one way to find out
if the throttle plate is being held open by bad adjustment of the linkages.

No... I am in New Zealand which is close to Australia and to the South Pole

Cheers... jondee86

Thank you so much Jondee86, the problems are getting much clearer now. I will pull out the Throttle Body this week and start work on it. I will keep this post updated and see if i could solve the problem at the end.

jondee86 wrote:No... I am in New Zealand which is close to Australia and to the South Pole

This also means all of his advice is upside down.

yoshimitsuspeed wrote:

jondee86 wrote:No... I am in New Zealand which is close to Australia and to the South Pole

This also means all of his advice is upside down.

It is nothing more than a historical quirk that puts Europe at
the top of the map. The truth is (and your government does not
want you to know this) that NZ is UP and you all are DOWN



Cheers... jondee86

jondee86 wrote:

yoshimitsuspeed wrote:

jondee86 wrote:No... I am in New Zealand which is close to Australia and to the South Pole

This also means all of his advice is upside down.

It is nothing more than a historical quirk that puts Europe at
the top of the map. The truth is (and your government does not
want you to know this) that NZ is UP and you all are DOWN



Cheers... jondee86

Oh, the conspiracy!

Wow that map makes my head hurt haha.
Took me a min to even find my country.

Most interesting map ive ever seen!! HaaHaaHaa!

So i took my whole throttle body off on the ground today. I noticed that the three valves in the fourth cylinder are not closed like the other three cylinders, is this something normal or are they stuck open? Last time i took the TB off, i think i remember that all four cylinders have all of their valves closed. Should they all closed when the engine is off?

As you can see from this pic....



... the four sets of cam lobes are set at 90 deg apart. Very often the
engine will stop with two sets of valves partly open, but it is possible
for it to stop with one set fully open and the others closed.

Cheers... jondee86