4AGE Blacktop 20V IACV

GNG45
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4AGE Blacktop 20V IACV

Postby GNG45 » Mon Aug 26, 2019 3:22 pm

Hello, are there any USDM IACV's that are compatible with the 20V IACV? I bought a used one on ebay after experiencing a high idle with my old one and now I have a rough idle.

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Re: 4AGE Blacktop 20V IACV

Postby Straitup D » Sat Aug 31, 2019 9:10 am

I have one, i will sell CHEAP, came off a running / driving car. if you do Text me at 9529133057 i dont use the forum much

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jondee86
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Re: 4AGE Blacktop 20V IACV

Postby jondee86 » Sat Aug 31, 2019 4:43 pm

GNG45 wrote:Hello, are there any USDM IACV's that are compatible with the 20V IACV?
I bought a used one on ebay after experiencing a high idle with my old one
and now I have a rough idle.

Have you tried cleaning the valve (blasting carb cleaner down the tubes until
no more black stuff comes out)??

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: 4AGE Blacktop 20V IACV

Postby GNG45 » Sat Sep 07, 2019 11:46 am

jondee86 wrote:
GNG45 wrote:Hello, are there any USDM IACV's that are compatible with the 20V IACV?
I bought a used one on ebay after experiencing a high idle with my old one
and now I have a rough idle.

Have you tried cleaning the valve (blasting carb cleaner down the tubes until
no more black stuff comes out)??

Cheers... jondee86


I sprayed it with brake cleaner. Definitely was dirty but still idles rough. It sounds like a muscle car. I ordered a refurbished IACV on eBay. Let's hope it works.

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Re: 4AGE Blacktop 20V IACV

Postby jondee86 » Sat Sep 07, 2019 10:00 pm

The ISCV modulates (changes position smoothly) the amount of idle air entering
the engine by opening and closing as instructed by the ECU. If you like, it will
change the engine speed much as if you were keeping the engine running by
gently opening and closing the throttle a fraction.

It is unlikely that the ISCV would actually CAUSE a rough idle. But if the engine
rpm was fluctuating because af misfiring, the ISCV might be trying to catch a
falling rpm and overcompensating. My engine sometimes gets a bit of a rich/lean
lope, and the ISCV can magnify that into a huge "supercharger lope" :) Sounds like
I have a cammed 427 with a 671 on top :)

So if the replacement ISCV does not cure the roughness, you will need to look at
things like the TPS setting, plugs and ignition timing.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: 4AGE Blacktop 20V IACV

Postby GNG45 » Sun Sep 15, 2019 1:24 pm

jondee86 wrote:The ISCV modulates (changes position smoothly) the amount of idle air entering
the engine by opening and closing as instructed by the ECU. If you like, it will
change the engine speed much as if you were keeping the engine running by
gently opening and closing the throttle a fraction.

It is unlikely that the ISCV would actually CAUSE a rough idle. But if the engine
rpm was fluctuating because af misfiring, the ISCV might be trying to catch a
falling rpm and overcompensating. My engine sometimes gets a bit of a rich/lean
lope, and the ISCV can magnify that into a huge "supercharger lope" :) Sounds like
I have a cammed 427 with a 671 on top :)

So if the replacement ISCV does not cure the roughness, you will need to look at
things like the TPS setting, plugs and ignition timing.

Cheers... jondee86


Changed out the ISCV. Still idles rough. I have a strong gas smell and when I rev the engine I see white smoke. I pulled all 4 plugs and they are black. I'm going to change out the plugs Should I check the TPS or ignition first?

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Re: 4AGE Blacktop 20V IACV

Postby jondee86 » Sun Sep 15, 2019 5:49 pm

Make sure that the hose for the MAP sensor is not split or leaking. Check that the
water temperature sensor for the ECU is not broken ior unplugged. Black plugs usually
mean that the engine is running rich. Once you have checked the above put in a new
set of plugs, then check the TPS setting and ignition timing.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: 4AGE Blacktop 20V IACV

Postby GNG45 » Wed Sep 18, 2019 4:38 pm

jondee86 wrote:Make sure that the hose for the MAP sensor is not split or leaking. Check that the
water temperature sensor for the ECU is not broken ior unplugged. Black plugs usually
mean that the engine is running rich. Once you have checked the above put in a new
set of plugs, then check the TPS setting and ignition timing.

Cheers... jondee86


The map sensor hose is getting brittle so I'm just going to replace it. It didn't have clamps on it and I'm not sure if putting some on would crack the plastic damper. Also would it be wise to change the plastic damper?

My water temp sensor connector was replaced about a month ago because I mistakenly pulled the wires out of the plug. It threw a code but after replacing the connector no code.

Plugs are coming in Friday. I found this video below would I adjust the TPS on a blacktop the same way (with the exception of where he puts the feeler guage and voltage.) https://www.youtube.com/watch?v=k7jS1y70S98

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Re: 4AGE Blacktop 20V IACV

Postby jondee86 » Wed Sep 18, 2019 10:30 pm

I don't remember ever using clips on MAP sensor hoses. If there are any they
will be tiny wire type clips that don't exert much force. Generally I have just
pushed then on and if you have the right size hose it w'ont fall off.

For TPS adjustment read this...
http://www.trinituner.com/v4/forums/vie ... 8#p6303405

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: 4AGE Blacktop 20V IACV

Postby GNG45 » Mon Sep 23, 2019 2:41 pm

Just an update. I changed out the plugs, reconnected the MAP, and shortened my throttle cable. There was some slack on it and I had no more tension so now the tension I can get it to sets the idle at is 2K RPM. I have feeler gauges coming tomorrow and I will adjust the TPS.

My idle is erratic as seen in the video. This happens once the car warms up. It's happened in the past with different ISCV. I checked to see if there was air in the coolant but none from running the car for 15 minutes. I did notice that when the idle surges the coolant goes up and drops when the idle drops.

https://www.youtube.com/watch?v=I_jC996Ysfg

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Re: 4AGE Blacktop 20V IACV

Postby jondee86 » Tue Sep 24, 2019 12:24 am

Cycling on the fuel cut... engine speed above around 1700 rpm and closed throttle.
Back the engine speed down to 1500 - 1600 rpm and it will stop doing that :)

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: 4AGE Blacktop 20V IACV

Postby GNG45 » Tue Sep 24, 2019 12:41 pm

jondee86 wrote:Cycling on the fuel cut... engine speed above around 1700 rpm and closed throttle.
Back the engine speed down to 1500 - 1600 rpm and it will stop doing that :)

Cheers... jondee86


You lost me there. What should I do?

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Re: 4AGE Blacktop 20V IACV

Postby jondee86 » Tue Sep 24, 2019 2:42 pm

First up you don't want your throttle cable to be tight. The throttle arm must return
and rest on the throttle stop to make sure that the throttle butterfly is fully closed
when you are off the gas, The cable itself should have just a little bit of slack so it
cannot hold the throttle arm off the throttle stop.

The ECU is set up to cut fuel delivery to the engine when the car is on the overrun
with a closed throttle. There are preset limits to control when the fuel is cut off and
basically the engine speed needs to be above 1700 rpm and the throttle closed before
fuel cut happens. Once the fuel is cut, the engine speed needs to drop below 1400 rpm
or therfabouts before the fuel turns back on (or you open the throttle).

Now we get to the trick part that I am not totally sure about. With quad throttles
the throttle butterflys only have to be cracked open by a tiny amount to push the idle
speed up. Most aftermarket ECU's call the throttles closed when they are less than
1% open, which means you can actually have a 2000 rpm idle even though the ECU
considers the throttles closed and initiates fuel cut. A vacuum leak will cause the
same issue by raising the idle with closed throttles.

So the idle speed goes high... fuel cut occurs.... idle speed drops... fuel is restored...
idle speed goes up... fuel cut occurs.... and there you have it :)

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: 4AGE Blacktop 20V IACV

Postby GNG45 » Thu Sep 26, 2019 5:42 pm

jondee86 wrote:First up you don't want your throttle cable to be tight. The throttle arm must return
and rest on the throttle stop to make sure that the throttle butterfly is fully closed
when you are off the gas, The cable itself should have just a little bit of slack so it
cannot hold the throttle arm off the throttle stop.

The ECU is set up to cut fuel delivery to the engine when the car is on the overrun
with a closed throttle. There are preset limits to control when the fuel is cut off and
basically the engine speed needs to be above 1700 rpm and the throttle closed before
fuel cut happens. Once the fuel is cut, the engine speed needs to drop below 1400 rpm
or therfabouts before the fuel turns back on (or you open the throttle).

Now we get to the trick part that I am not totally sure about. With quad throttles
the throttle butterflys only have to be cracked open by a tiny amount to push the idle
speed up. Most aftermarket ECU's call the throttles closed when they are less than
1% open, which means you can actually have a 2000 rpm idle even though the ECU
considers the throttles closed and initiates fuel cut. A vacuum leak will cause the
same issue by raising the idle with closed throttles.

So the idle speed goes high... fuel cut occurs.... idle speed drops... fuel is restored...
idle speed goes up... fuel cut occurs.... and there you have it :)

Cheers... jondee86


Okay makes more sense. I replaced the cable and it idled at around 2100 rpm. Once the car warmed up it began to idle erratically again. I removed the throttle cable to see if the idle changed and it stayed the same.

It's hard to tell because I have mesh over the ITB's but I'm wondering if they are open to wide. Maybe I should start closing them little by little to see if the idle changes.

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Re: 4AGE Blacktop 20V IACV

Postby jondee86 » Thu Sep 26, 2019 8:32 pm

Remove the filter from the fresh air side of the ISCV and block the end of the
tube with your thumb. You should be able to regulate the idle speed by varying
the amount of "blocking" you are applying with your thumb. Tptally blocked the
engine should either stall or drop to a very low idle like 400-500rpm. If it does
not behave like this then your engine is getting idle air from someplace else.
Either the throttles are not fully closed or there is a vacuum leak.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: 4AGE Blacktop 20V IACV

Postby GNG45 » Sun Sep 29, 2019 11:56 am

jondee86 wrote:Remove the filter from the fresh air side of the ISCV and block the end of the
tube with your thumb. You should be able to regulate the idle speed by varying
the amount of "blocking" you are applying with your thumb. Tptally blocked the
engine should either stall or drop to a very low idle like 400-500rpm. If it does
not behave like this then your engine is getting idle air from someplace else.
Either the throttles are not fully closed or there is a vacuum leak.

Cheers... jondee86


I blocked it off and the idle dropped to around 700 rpm. It took about a minute or so before it stalled out. I ended up using a synchrometer on the ITB's and they all read varying numbers over 3 kg/h. I lowered them to around 1.8 kg/h and the car idled at around 1800 rpm. Whenever I gave it throttle it idled like in the Youtube video once and then stayed at 2200 rpm. I took the car out for a drive and it idled either at 1800 rpm or 2200 rpm, I would get that surge once and then it would idle at 2200 rpm. I started the car this morning because I wanted to wash it and it started to do that surge again. I checked the kg/h on the ITB's and they are all between 1.8 and approximately 2.3. The adjuster screw is getting much harder to screw so I'm going to give it a second try and probably start replacing all the vacuum hoses.

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Re: 4AGE Blacktop 20V IACV

Postby jondee86 » Sun Sep 29, 2019 2:37 pm

I feel that you are treating the symptoms rather than finding the cause of this problem.
On a 20V ALL the idle air should be passing thru the ISCV. If the engine can idle at 2000 rpm
with closed throttles, then either the ISCV is not closing or the throttles are not closing fully
and there is excessive air leakage past the throttle plates.

It is not possible to have the throttle plates closing 100% air tight, so the small bleed screw
provided on each throttle is used by the factory to make a final adjustment to balance the
leakage so that all throttles are the same. In the OEM setup the bleed screws are covered
indicating that they are not considered a user-adjustable item.

However, to compensate for wear and minor misalignment issues, each throttle has an
adjustable throttle stop and an adjustment to make sure all throttles open simultaneously.
Providing you are using the factory manifold the adjustments required will be minimal but
they will need to be checked and adjusted if necessary to make sure all throttles are closing
completely and opening at the same time (not one or two cracking open before the others
have moved).

Outside of this you have the vacuum operated servo throttle opener. If you still have this
connected, make sure that the push rod retracts clear of the throttle operating arm when
the engine is idling. If it does not retract far enough it will prevent the throttles from closing
fully at idle.. There is adjustment on the pusher rod.

And finally the ISCV itself. If you cleaned it but did not dislodge all the black crud from the
rotating cylinder, it may be sticking partially open. To be sure that it is clean it would be
best to take it off the engine and then remove the plastic enclosed solenoid. This allows
you to rotate the valve by hand and feel if it is free to move in both directions.

DO NOT remove the cover plate from the other end of the valve. There is a bi-metallic
spring inside that holds the valve in a neutral position. The spring is factory adjusted and
sealed and it is not a user-adjustable item. If the cylinder rotates freely in both directions
but you do not feel resistance from the spring and the cylinder does not return to the centre
position, then the spring is broken and you need another ISCV.

Rotate the cylinder by hand and continue cleaning until all the black stuff is removed and
the cylinder returns freely to the centre position from both directions. Let it dry, lubricate
with a squirt of CRC and re-assemble. You have now covered all the bases and the ECU
should be able to hold the correct idle.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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