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Discussion Starter · #1 · (Edited)
Well, I know I have an exhaust leak, it's because it's not welded on yet, but listening to it idling, I'd appreciate input. (link goes to a 20sec youtube video)
4age test <--link
To those who are new, the engine is a 4AGE Blacktop 20v swap. Do note that engine is running rich, idling is low, spark plugs are new, fuel injectors are new and test compression shows 200PSI in every cylinders.

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First
, in the picture below, I have adjusted the #2 screw for idling, but all I notice is car idles high to crank and then RPMs drop back to where it is like in the video.
I know there are other screws which I believe are called hardstop around each TB (#1, #3, #4). Are those the one I'm supposed to adjust to have a higher idle?
What does #2 really do, is it only changing the cranking idle and then stops because of some vacuum system?
Green Blue Circuit component Toy Audio equipment


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Second
, I have this tube that sucks air in when the engine idles. I've seen it going to the airbox in stock setups, but since I dont have one, I am not sure whether I should block it or not.
EDIT: From what I've found, I should just add a filter on it and leave it open.
Hood Automotive tire Motor vehicle Electrical wiring Vehicle


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Third
, I've briefly test drove the car. It drives and all, but the throttle response with ITB's seems really slow, I have also let my friend drive it and he thought the same. anyone know any reasons that could cause this?
From what I've found online, it could be dirty fuel system or vacuum leak.

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Finally
, I have a voltage gauge installed that shows around 10V continuously. My battery is new and shows 12.54V with an external voltmeter. Could that cause the sparks to be weaker, or anything of the sort?

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From all of this being said and after watching the video, what would you guys say are the next step and what issues I could possible have?
I'm wondering if I have weak sparks,even a misfire or a worn clutch for the throttle response, but I can't really tell.

Cheers,
 

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Well it defenitly doesn't sound rights, that's for sure! And throttle respons with ITB's should be crisp and quick.

I'd start at the basics: Have you checked iginition timing and confirmed you have spark on all 4 cylinders? Check all vacuum lines for leaks and check if you have good fuel pressure
Are you running the OEM ECU? Is the MAP sensor getting the right vacuum?

The hose you are holding there is the valve cover ventilation and should be left open. Putting a filter on it would be smart to prevent dust or debris getting into your cylinderhead...

And with 10 Volts, you alternator isn't charging your battery. The 12.5V measured at the battery is with the engine running?
With engine running, voltage at the battery posts should be around 14 Volts...
 

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Very cool, I've been eyeing a 20V Silvertop for a swap into my GTS potentially!

Definitely agree, first things first make sure your alternator is actually charging the battery and you're getting around 14V (use a multimeter). Also make sure you're connections and grounds are all making good contact. In my experience bad electrical (specifically grounds, low voltage, bad connections) can cause weird problems, things that let the car run, but with some strange issues.

Once you've confirmed your electrical is looking okay, check your ignition timing with a timing light and ensure that you're getting spark.

Then I'd make sure there are no vacuum leaks, especially since you have individual intakes and not the common air box that usually covers all four throttles. I'm not super familiar with the ITBs, so I can't remember in the setups I've seen if each throttle has a vacuum reference line or something similar? If those aren't connected you could have some good vacuum leaks.

Would also be good to know if you're using the OEM ECU or an aftermarket option, and what other mods might have been made.
 
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Very cool, I've been eyeing a 20V Silvertop for a swap into my GTS potentially!

Definitely agree, first things first make sure your alternator is actually charging the battery and you're getting around 14V (use a multimeter). Also make sure you're connections and grounds are all making good contact. In my experience bad electrical (specifically grounds, low voltage, bad connections) can cause weird problems, things that let the car run, but with some strange issues.

Once you've confirmed your electrical is looking okay, check your ignition timing with a timing light and ensure that you're getting spark.

Then I'd make sure there are no vacuum leaks, especially since you have individual intakes and not the common air box that usually covers all four throttles. I'm not super familiar with the ITBs, so I can't remember in the setups I've seen if each throttle has a vacuum reference line or something similar? If those aren't connected you could have some good vacuum leaks.

Would also be good to know if you're using the OEM ECU or an aftermarket option, and what other mods might have been made.
Thinking along those lines, I'd look for vacuum leaks at the base of the ITB's where they bolt to the manifold, also at the manifold to head connection. I only say that as my VW runs dual carbs, and a vacuum leak at the base of one (or even at the manifold to head connection) will effect the other in over all running, tuning, and even idle speed. Speaking of idle speed, is it high or low? It should be around 650 to 750 rpm. If it's higher, you'll have to adjust the timing down some to get the advance to work better with the ITB's.
I have to agree with the others, the ITB's should run like a scalded ape. Especially down low or everywhere in between. If they're not, then I'd also check fuel pressure, and make sure the throttle linkage is opening all 4 equally and evenly (synchronized). I have to check my dual carbs every now and then, as the fuel changes in quality. So, I'd double check for vacuum leaks, and double check your timing and advance. Start with the basics, then move on to other areas.
And yes, double check your voltage output of your alternator. Some FI systems like to operate at a minimum voltage, and most times when it drops below a certain value will run rich or lean (depending on the system). Just something to think about.
 

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Discussion Starter · #5 ·
Well it defenitly doesn't sound rights, that's for sure! And throttle respons with ITB's should be crisp and quick.

I'd start at the basics: Have you checked iginition timing and confirmed you have spark on all 4 cylinders? Check all vacuum lines for leaks and check if you have good fuel pressure
Are you running the OEM ECU? Is the MAP sensor getting the right vacuum?

The hose you are holding there is the valve cover ventilation and should be left open. Putting a filter on it would be smart to prevent dust or debris getting into your cylinderhead...

And with 10 Volts, you alternator isn't charging your battery. The 12.5V measured at the battery is with the engine running?
With engine running, voltage at the battery posts should be around 14 Volts...
Sorry, I missed the notification hence the late reply. Ignition timing is good and I have sparks on all 4 cylinders. I just changed my altenator for the second time now (all used previously) and the car runs a lot smoother. But when I checked voltage while running, battery showed just under 12, around 11.9V. Before running, the battery was at 12.54V.

Although the car seems to runs smoother, I'm sure it could be better if the voltage is right.

Very cool, I've been eyeing a 20V Silvertop for a swap into my GTS potentially!

Definitely agree, first things first make sure your alternator is actually charging the battery and you're getting around 14V (use a multimeter). Also make sure you're connections and grounds are all making good contact. In my experience bad electrical (specifically grounds, low voltage, bad connections) can cause weird problems, things that let the car run, but with some strange issues.

Once you've confirmed your electrical is looking okay, check your ignition timing with a timing light and ensure that you're getting spark.

Then I'd make sure there are no vacuum leaks, especially since you have individual intakes and not the common air box that usually covers all four throttles. I'm not super familiar with the ITBs, so I can't remember in the setups I've seen if each throttle has a vacuum reference line or something similar? If those aren't connected you could have some good vacuum leaks.

Would also be good to know if you're using the OEM ECU or an aftermarket option, and what other mods might have been made.
would be interesting to see someone else have a similar build!
I made sure the alternator connector and the 2 wires that bolt on the alternator are clean. My ground to battery is clean and I've changed my altenator (for the second time). The engine runs smoother but multimeter shows 11.9V at battery terminals when engine is running.

I'm not sure if why my battery shows under 12V considering its the 3rd alternator I've put in this car.

Engine is stock beside the airfilter box, fuel pump is aftermarket OEM ECU

Thinking along those lines, I'd look for vacuum leaks at the base of the ITB's where they bolt to the manifold, also at the manifold to head connection. I only say that as my VW runs dual carbs, and a vacuum leak at the base of one (or even at the manifold to head connection) will effect the other in over all running, tuning, and even idle speed. Speaking of idle speed, is it high or low? It should be around 650 to 750 rpm. If it's higher, you'll have to adjust the timing down some to get the advance to work better with the ITB's.
I have to agree with the others, the ITB's should run like a scalded ape. Especially down low or everywhere in between. If they're not, then I'd also check fuel pressure, and make sure the throttle linkage is opening all 4 equally and evenly (synchronized). I have to check my dual carbs every now and then, as the fuel changes in quality. So, I'd double check for vacuum leaks, and double check your timing and advance. Start with the basics, then move on to other areas.
And yes, double check your voltage output of your alternator. Some FI systems like to operate at a minimum voltage, and most times when it drops below a certain value will run rich or lean (depending on the system). Just something to think about.
Sorry, I missed the notification hence the late reply. Timing is right, I dont think Ive found any vacuum leak, and I put another alternator (3rd one) with still 11.9V at battery when car is running.
 

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Something is not right in the charging system. I say that because you should have 14.7 volts. Most 12 volt systems run higher voltage than spec'd because there is a need to charge the battery after starting, and headlight use is a very large amp draw. Go thru all of the charging system. You might have a bad diode or voltage regulator inside the alternator. It's not the first time I've run into that, and with parts coming from who knows where, ALL new parts are suspect.
I know on some EFI systems that anything below 12.5 volts will cause it to run rich or lean. My wife's 52 year old EFI VW will run rich is the voltage is below 12.4 volts.
 

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Discussion Starter · #7 ·
Something is not right in the charging system. I say that because you should have 14.7 volts. Most 12 volt systems run higher voltage than spec'd because there is a need to charge the battery after starting, and headlight use is a very large amp draw. Go thru all of the charging system. You might have a bad diode or voltage regulator inside the alternator. It's not the first time I've run into that, and with parts coming from who knows where, ALL new parts are suspect.
I know on some EFI systems that anything below 12.5 volts will cause it to run rich or lean. My wife's 52 year old EFI VW will run rich is the voltage is below 12.4 volts.
ok I'll test the diode then. As for the regulator, can I just unplug it to see the voltage at the battery when the car is running or unplugging it might be harmful?
It's thesecond alternator I have bought already so hopefully wiring is the issue
 

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There are also 2 fuses used for te alternator AL1 and AL2 if my memory serves me correctly. One is a main fuse, and the other is the one between the diode and alternator light and the alternator itself. You might want to check those as well.

But frankly, if either was blown, or the diode would be bad, the battery light would come on and stay on to indicate that the charging system isn't working properly.
But with alternator working as it should, with a runnign engine, you should always measure at least 14 volts at the battery posts.
 

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Discussion Starter · #9 ·
There are also 2 fuses used for te alternator AL1 and AL2 if my memory serves me correctly. One is a main fuse, and the other is the one between the diode and alternator light and the alternator itself. You might want to check those as well.

But frankly, if either was blown, or the diode would be bad, the battery light would come on and stay on to indicate that the charging system isn't working properly.
But with alternator working as it should, with a runnign engine, you should always measure at least 14 volts at the battery posts.
I'll check that out. Diagnosing is a bit difficult since some components like dash arent completely wired.
Thanks
 

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Well, that might already be part of the problem. The battery check light is part of the circuit to 'activate' the alternator:

The importance of having an operational warning light for the alternator (idiot light) is crucial to catching problems early. In most modern systems, the electrical current passing through the filament of the warning light is what energizes a circuit in the alternator to start charging.
So if that light isn't wired up correctly yet, the alternator itself might be fine and spinning. But if the alternator doesn't get the signal through that light, it will not start charging...
 

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Discussion Starter · #11 ·
Well, that might already be part of the problem. The battery check light is part of the circuit to 'activate' the alternator:



So if that light isn't wired up correctly yet, the alternator itself might be fine and spinning. But if the alternator doesn't get the signal through that light, it will not start charging...
I see, I did see something like that on youtube videos, but never understood fully..
You have any idea on how I could trace something like that to fix it?
 

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Wiring diagrams would be a good start I guess :LOL:

But if you know which wire is used for the battery light, that would be a good start. It should go from the gauge cluster to a dedicated fuse in the fusebox under the hood, and from there run to the connector on the alternator.
 

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The 3 small wires going to the alternator, I believe the yellow one goes to the warning light. The other 2 wires, one should have battery voltage all the time, the other has battery voltage only when the key is ON. Check these with the engine off.

The alternator should stay above 12.6 volts when running to maintain the charge on the battery. If you rev the engine does the voltage increase? Mine drops below 12.6 at idle if I have accessories on and the brake lights which I suspect is the diodes in the bridge rectifier, but I don't drive my 1990 too much, so I haven't fixed or replaced the alternator yet, and I have a voltmeter USB charging device in the cigarette light socket to monitor the voltage.
 
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Discussion Starter · #14 ·
Wiring diagrams would be a good start I guess :LOL:

But if you know which wire is used for the battery light, that would be a good start. It should go from the gauge cluster to a dedicated fuse in the fusebox under the hood, and from there run to the connector on the alternator.
its hard out here as someone whos learning 😔
I've seen online that you have a sense, lamp and ignition wire. I'll try to trace them
The 3 small wires going to the alternator, I believe the yellow one goes to the warning light. The other 2 wires, one should have battery voltage all the time, the other has battery voltage only when the key is ON. Check these with the engine off.

The alternator should stay above 12.6 volts when running to maintain the charge on the battery. If you rev the engine does the voltage increase? Mine drops below 12.6 at idle if I have accessories on and the brake lights which I suspect is the diodes in the bridge rectifier, but I don't drive my 1990 too much, so I haven't fixed or replaced the alternator yet, and I have a voltmeter USB charging device in the cigarette light socket to monitor the voltage.
Is the voltage regulator built inside the alternator?
Apparently the sense wire connects to the battery side of the voltage regulator. I assume that one should go directly to the + battery.
You have a lamp wire which is the warning light on the dashboard which would be the yellow one.
And you have an ignition wire which would be only on when key is on and act as a signal to start charging.

Correct me if I'm wrong, but those are my deductions from what I understood
 

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Well, that might already be part of the problem. The battery check light is part of the circuit to 'activate' the alternator:



So if that light isn't wired up correctly yet, the alternator itself might be fine and spinning. But if the alternator doesn't get the signal through that light, it will not start charging...
Agreed. I suppose you could temp wire in an alt light and see if that makes a difference.
 

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its hard out here as someone whos learning 😔
I've seen online that you have a sense, lamp and ignition wire. I'll try to trace them

Is the voltage regulator built inside the alternator?
Apparently the sense wire connects to the battery side of the voltage regulator. I assume that one should go directly to the + battery.
You have a lamp wire which is the warning light on the dashboard which would be the yellow one.
And you have an ignition wire which would be only on when key is on and act as a signal to start charging.

Correct me if I'm wrong, but those are my deductions from what I understood
I believe those wires are correct, but not 100% sure. Yes, it's part of the rectifier bridge, the diodes, and a heat sink, along with a solid state regulator (non-serviceable), that should be attached to one side of the heat sink or case body. It's really amazing how they (the manufacturers) get all of that stuff inside the alternator along with the brushes and brush holder. Usuallly the brush holder sits on top of the VR, and is screwed on to hold both in place. There's also a thermal grease used to help with heat transfer between the VR and the case body (at least in those I've had apart). I hope this helps.
 

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Discussion Starter · #17 ·
I believe those wires are correct, but not 100% sure. Yes, it's part of the rectifier bridge, the diodes, and a heat sink, along with a solid state regulator (non-serviceable), that should be attached to one side of the heat sink or case body. It's really amazing how they (the manufacturers) get all of that stuff inside the alternator along with the brushes and brush holder. Usuallly the brush holder sits on top of the VR, and is screwed on to hold both in place. There's also a thermal grease used to help with heat transfer between the VR and the case body (at least in those I've had apart). I hope this helps.
do you know if I could just wire the 3 pins myself? I saw a few diagrams and none of them were wired to any important components like the ECU. So theorically wiring it DIY wouldn't be harmful?
 

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Discussion Starter · #18 · (Edited)
UPDATE:
I tried diagnosing the charging system earlier today and here's what I found out:
1) There doesn't seem to be a voltage drop
2) Using a multimeter, B+ alternator with battery negative terminal, I measured nothing. Could it simply not be charging without the dummy light or did I measure it wrong?
3) Battery showed 12.74V before starting the car, and 12.65V after running for 5 mins. While running, it was at 11.6V.

I have limited knownledge and am constantly learning by myself, so I would like you guys to give me thoughts on my plan:
I want to do a DIY wiring for the alternator charging system.
There is a 3 pin connector connected to the alternator, which are sense wire (to B+), fused lamp wire (which isn't mandatory for functionnality?) and fused ignition wire (to ignition key ON). This wiring part should be easy and simple. I was thinking on not using the harness connector and plug directly into alternator pins.

For the B+ alternator post, I plan on running one 10AWG wire with a fuse directly to the battery positive terminal (LIKE SHOWN ON DIAGRAM).
In order to do all this, I will leave the current charging wiring system like it is and ADD ONE MORE wire to B+. (side note: why are there 2 wires going to the B+ post?)

The charging system doesnt seem to be wired to the ECU, so I think it should work, correct me if I'm wrong.

Rectangle Slope Font Parallel Schematic
 

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I don't know why it has 3 different white wires going to the alternator. Especially since 1 goes to the sensing part which should be the warning light. The 2 white wires should go to the big main terminal on the alt. Sorry, I'm more used to working with GM alternators, and converting them to basically 1 or 2 wire set ups is easier to do, as you bring a battery connection to the large terminal, then connect a jumper wire (red) to the plug. For 1 wire you just don't add a charging light, or you use the other terminal (brown) for the light (2 wire set up, that actually uses 3 wires).
The alternator wiring doesn't directly go to the ECU, but rather to the fuse box where it powers everything else in the car including the ECU.
I'll never understand how the Japanese do wiring sometime, and it's similar but not the same as the German wiring systems which are easier to figure out. example: Red is hot all the time, black is hot with key on, and brown/tan is ground.
 

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I have the complete wiring diagram and diagnostics description in the factory manuals in my workshop. I could easily explain it to you with the schematics, but I just don't have them at hand at the moment. I do swing by my workshop tomorrow if you can wait for that.

It is not hard to wire up a alternator. It has nothing to do with the ECU or anything like that, and is sort of a complete separate system. You can make the alternator run that way, but I don't think it would be hard to make the existing wiring work too. Only a few things to check and with the correct wiring diagram I can tell you where to measure what and what to connect to make it all work.

I'll never understand how the Japanese do wiring sometime, and it's similar but not the same as the German wiring systems which are easier to figure out. example: Red is hot all the time, black is hot with key on, and brown/tan is ground.
If you have the right schematics, it's pretty easy to understand if you ask me. But I'm used to them, so it might just be what you work with every day 😏
 
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