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Discussion Starter · #1 ·
Gday,

I trying to nut out a problem I have with my Patrol. I own a 2005 GUIV with a ZD30 coupled to an auto.
Ever since I've owned it, it’s has a problem with performance when cold or when it sits for a while and the engine not running.
It is very slow and sluggish and then after driving it for five minutes, out of the blue it has the power it is suppose too. It sometime has really good power if it sits idling for 10min and then take it for a drive.
My father in-law has the same model but it has a manual and that drives the same no matter cold or even if it has been driven +100km. I’d admit I’m jealous!
I have fitted a Dawes, needle and EGR plate but that did not fix this annoying fault.

I have a feeling it might be because of low vacuum. I replaced all the hoses and its still the same so I tested the vacuum using a gauge.
The pump has two inlet and I am getting two different reading

The one going to the VNT is reading 54KPa (300mm.Hg) and other for the Swirl control/intake air control solenoid valve is reading 80KPa (560mm.Hg)

The manual said
Start the engine, and measure the load pressure with the engine idling.
Vacuum pressure:Standard −93.3 to −101.3 kPa (−933 to −1,013 mbar, −700
to −760 mmHg, −27.56 to −29.92 inHg


It doesn't say to test each intake individually. Should the pressure be the same? It obvious the pump is reading below spec.
 

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Y2KGUII ZD Wgn
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Carefully inspect every mm of your vacuum lines again for leaks, did you miss one? There is one point where the lines comes out from under the IC that is prone to wearing through if a couple of brackets have been misaligned over the years.

My old girl has always been a bit low in comparison to what others have put up, I have 26"Hg at idle so I'm a little under the recommendation but that has never been a problem for it. Sorry I'm an old Engineer and still think in "Hg.

Your description is around 12"Hg on one and 22"Hg on the other, what I would do is go directly to the line under the front of the IC that feeds this gear and connect your gauge there directly, meaning everything else is bypassed, so you should be seeing highest Vac possible, if you are getting a good reading there then you are losing it somewhere else.

Don't forget there are actually 2 lines under the IC one of them feeds the solenoids that control swirl and main shutdown valve the other goes to the VNT gear, so you really need to remove the IC to inspect fully.

Let us know what you come up with.

BTW, you can block the one to the swirl valve no worries, that's the one at the back, leave the valve closer to the front connected, that is important.
 

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I also have a GU IV 2005 ST auto and yes it seems to take a while to spool up when cold but that is partly the auto box is sluggish to lock the torque converter till it is warmed up.

I tested the vacuum at idle connected to the VNT, I get about 22 to 25"Hg at idle and it climbs to 30 to 35 when reving 2000 to 3000rpm.

So if you are measuring at idle then it is about the same as mine. Cold mornings you do need to take it slow till it warms up.
 

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Discussion Starter · #4 ·

I pulled the intercooler off and made sure everyone was replaced and followed a vacuum drawing for the ZD30. I suppose back to my original question are there meant to be two different pressures coming from the same pump?
VNT side is at 16"Hg (this pressure doesn't not change when the rpm increases)
Control Valves side 25"Hg (27"Hg when RPM increases)

The is no way the ECM can read the vacuum pressure...right?

Big thanks to you guys for your knowledge
 

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Y2KGUII ZD Wgn
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Mate, just to verify all this I did a trial on mine a few minutes ago, I connected the vac gauge to the vac tube under IC that goes to the throttle body valves and blocked the one to the VNT took a reading and then did the reverse, engine was dead cold at 24C and I achieved 27.5"Hg on both sides (hmmm just a touch higher than my readings of the past), so you are leaking somewhere.

Try it again as I did, blocking it's opposite number that will give you a true indication of what the vac pump is doing and where the leak may be hiding.
 

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Y2KGUII ZD Wgn
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You can check the VNT by simply attaching a piece of tube to the VNT, sucking like crazy to lift the VNT arm, then put your tongue over the end of the tube and see if the arm holds position for a short while, this simple test can be done on the Dawes as well. Takes about 30 seconds and answers the question. If there is a leak at the Dawes pull it apart and see if there is any debris in there, happens from time to time.

If you have a look in my sig there's a link to my channel, I did a video about pulling a Dawes apart and resetting it.
 

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Discussion Starter · #8 ·
Thank you from your idea. Found the leak coming from the needle valve. Connected gauge to VNT side, closed needle valve, start engine and vacuum press went up to 26"HG. I wonder if my I am adjusting the valve so its open to far?
The way i am adjusting it, is to start opening the valve and when the actuator starts to open , close it down until the actuator closes, leave it there.
 

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Y2KGUII ZD Wgn
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OK sorry we missed that asking you that, sometimes we take things for granted, all tests need to be done with the needle closed otherwise your venting to atmosphere. The way you are setting it up is the text book way and that's fine, I do it a little different, I set it to a spoolup rate that I want, depending on the circumstances I may want it set a little different. How far open is your needle valve? And what is your spoolup rate, give us some numbers at 1500 and 2000 in 3rd and tranny locked with it open to where you normally have it and then when it is closed, you may have it open too far.
 

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Discussion Starter · #10 ·
Yes silly me for not taking an open needle valve into account. I have never looked at the spool rate at a certain rpm but i wonder if it would be easy setting the valve using vacuum pressure.

With the needle closed, pressure is at 26"hm and VNT closed is at 16"HG. I've set it at the half way mark 21"Hg at idle and took it for a drive. I drove great! I'm happy but mind you the engine was warm.
I'm going to leave like that for a few day and monitor. I will get the spools at RPM too
If you down mind GU2 can you see what your pressure is set at for the VNT?
What is the pressure when actuator closes and your sweet point?
Your max is at 27.5"Hm
It might be an easier way you set up for noobs like me?
 

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Y2KGUII ZD Wgn
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Yes silly me for not taking an open needle valve into account. I have never looked at the spool rate at a certain rpm but i wonder if it would be easy setting the valve using vacuum pressure.

With the needle closed, pressure is at 26"hm and VNT closed is at 16"HG. I've set it at the half way mark 21"Hg at idle and took it for a drive. I drove great! I'm happy but mind you the engine was warm.
I'm going to leave like that for a few day and monitor. I will get the spools at RPM too
If you down mind GU2 can you see what your pressure is set at for the VNT?
What is the pressure when actuator closes and your sweet point?
Your max is at 27.5"Hm
It might be an easier way you set up for noobs like me?
For spoolup, no two are the same, as said earlier setting it up the way you did originally is the text book guide, I have data from years ago on mine on what it takes to move the arm and take it to the top and I've compared it to others and seen numbers on different vehicles between 9 and 13"Hg, so as said no two are alike, depends a lot on your mods, that's why I do it to a spoolup rate instead.

I have played a lot in the past with my VNT adjustment (one reason I don't use my Needle much these days) so it would be different to yours again.

I actually came across some old data I put together some years ago on revs/MAFv/boost/tps/T% (%vac the ECU sends to vac switch). I might do an update soon for a comparison against today and put it up.


Just for a laugh, how does it drive with the needle valve fully closed and then open 1/2 turn?
 

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Discussion Starter · #12 ·
I've only driven it a couple of times now and i can say there is an improvement but I want to drive it for about a week before I make a final judgement. So far thumbs up
 
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