[Emmett 2000 3ltDI]

Good evening all and thanks for all the information I have already used on this forum.

I have recently purchased a 2000 ZD30Di with a limp issue at cruising speed.
The following was done by previous owner through mechanics to try and fix the problem.
:New MAF
aws valve
:General service
:Check EGR, TPS

I have replaced the new MAF with a genuine one.
Looked for leaking vac or intercooler but seems ok.
Today I finally got the boost gauge on it and was expecting some sort of over boost problem
but instead got the following.
Seems somewhat normal until you put a fair bit of acceleration on it then it will drop from 14psi to 7psi
At cruising speed it will be at 14-15psi and sometimes limp (Lift accelerator and it will return power) .
At cruising speed if you put foot down it will drop boost from 14psi down to 5-6psi and take ages to build boost.
Seems that boost is high and drops massively when asked for power.
Most of the issues are above 2500 revs.

What next ladies and gentleman?
Any help or advice would be much appreciated.

 

[Emmett 2000 3ltDI]

BTW it is completely stock other than someone has bypassed the Vac tank after snapping the little white bit where the hose goes on. I have a new one coming just in case but unless it has had some vac hoses mixed up it should be ok..

 

[Emmett 2000 3ltDI]

I should also clarify the daws went in but came back out when it didn't fix the problem so completely stock at the moment. I would like to fix it before starting to install NADS so I know I am not masking a problem.

 

[Phdv61]

If you have a full stock PAtrol with non blocked EGR, and if nobody touched the turbo settings ( limiting screw, rod length), it should be fine. It is not, so your Patrol is no longer 'stock'.

If you got it with a dawes, it is very likely that the previous owner did some 'experiments' without knowing what he was doing. No worries, this can be fixed.

Everybody now knows what I think of the Dawes valve arrangement.
So I guess you still have your ECM controlling the Vacsol, + a dawes ( and needle, or not ?).

If your EGR is blocked, and if you still have your ECM controlling the Vacsol, it is a classic one to get limp modes.

A quick fix is to screw 1/3rd at a time the limiting screw ( or install a needle ). And you'd better add the dawes to limit boost peaks.

What happens is that your dawes keeps your vanes closed until you reach the boost at which it is set to open.
When it opens, vanes are suddenly fully opened. And you get a sudden loss of boost. That straight opening must be "smoothed".

One Dawes + one needle is a bare minimum. But you will never get a perfect setting. And you will have to compromise by opening a bit the needle otherwise you will keep bouncing.

Go to the thread "Dawes + 2 needle or 3...."
Enjoy the (long) reading. All necessary explanations are detailed in there. Some guys of this site became "experts" in setting multi-valves arrangements I have been suggesting.

 

[Phdv61]

Last but not least. Limp comes from MAF voltage exceeding what the ECM is happy with. You can either make the vanes to open more, and reduce boost/MAF voltage, or go or a fully electronic solution to keep the MAF voltage under control and optimize your turbo management.
Look for "Magic Box". Mine is a 2000 Di too.

 

[Emmett 2000 3ltDI]

Thanks so much for the reply.
It hasn't had a Daws in it since I have had it as it was taken back out by the mechanic when it didn't fix the problem. So you think that the VNT screw has been adjusted and not.returned to previous setting is causing these issues essentially by increasing MAF voltages?

 

[Emmett 2000 3ltDI]

No EGR block btw.

 

[Phdv61]

I really don't know what happened with your Patrol.
But if your Patrol is all stock, it is a possibility that the previous owner tried to increase the boost by unscrewing the limiting screw or reducing the actuator rod length. At 20 000km distance, it is hard to say. But this is where I would start with.

 

[Emmett 2000 3ltDI]

You may well be right and the thought had occurred to me too.
I had a look at the boost/vac solenoid this morning and it seemed clean and diaphragm was intact. After putting it back together and reinstalling it the boost still seems strange and some wired power issue still but for the first time it didn't limp.

 

[JoeBoy]

Mate mine does the exact same thing. Same patrol but a 2002. I haven't had the time to fix it properly at the moment, but it's a common issue on the ZD30DIs.

From the research I've done, it's the ECU controlled overboost protection. Basically when the engine runs at high boost for longer periods of time, the ecu limits the boost and drops it as you've described.

Search the forum for "ZD30 bible", there's a section that describes the issue. Although it doesn't give clarity as to what actually causes it other than faulty MAF.

Take a look at this screenshot for info:

 

[JoeBoy]

Actually after doing a re-read of the doc, it could be that the previous owner was doing alot of towing and wanted more low down power so adjusted the VNT.

 

[Emmett 2000 3ltDI]

Hard to say at this point. The boost maxes out at around 14 which I wouldn't have thought was too high and today after checking the boost solenoid it didn't limp but no change to boost levels I can see.
I have ordered a Tillix kit to bypass the boost solenoid now that the limp has stopped my working theory is that it could be failing boost solenoid.
I wanted to do my best to make sure it wasn't something else before starting NADS.
I'll let you all know how it goes.

 

[Phdv61]

You can spray some WD40 inside the solenoid to lubricate it.
Limp is not overboost. The overboost limit is much much higher.
Limp is due to the ECM cutting fuel from the IP if the MAF voltage exceeds a given voltage for too long ( 2s roughly) below 2000, below 2500, below 3000 and below 3500RPM.

 

[Emmett 2000 3ltDI]

A note on my issue though is that it will limp at almost any boost level but consistent holding of speed above 2600 revs (hence not being completely sold on the over boost limp being the problem, and it had a Daws put in to limit boost and it didn't work.

 

[Emmett 2000 3ltDI]

You can spray some WD40 inside the solenoid to lubricate it.
Limp is not overboost. The overboost limit is much much higher.
Limp is due to the ECM cutting fuel from the IP if the MAF voltage exceeds a given voltage for too long ( 2s roughly) below 2000, below 2500, below 3000 and below 3500RPM.

Thanks for that, goes a fair way to clarify my issue.
So bypassing the solenoid should have the desired effect then? Or will I need to organise a MAF voltage limiter of some kind?

 

[JoeBoy]

I

You can spray some WD40 inside the solenoid to lubricate it.
Limp is not overboost. The overboost limit is much much higher.
Limp is due to the ECM cutting fuel from the IP if the MAF voltage exceeds a given voltage for too long ( 2s roughly) below 2000, below 2500, below 3000 and below 3500RPM.

The problem isn't the car going into limp, it's overboost protection. If you block the egr and adjust the vnt the engine will still run the the overboost protection at crusing speeds at 14psi.

 

[JoeBoy]

A note on my issue though is that it will limp at almost any boost level but consistent holding of speed above 2600 revs (hence not being completely sold on the over boost limp being the problem, and it had a Daws put in to limit boost and it didn't work.

Could be the boost pressure sensor?

 

[JoeBoy]

There's some info here

3.0 TDI with erratic loss of boost - Page 2 - Nissan Patrol 4x4 (Africa)

 

[Phdv61]

above 2600 RPM, which means above 2500 RPM but below 3000 RPM, if your MAF voltage exceeds 3.88V for more than 2s, you will get limp.

 

[Bidja]

I have ordered a Tillix kit to bypass the boost solenoid now that the limp has stopped my working theory is that it could be failing boost solenoid.
I wanted to do my best to make sure it wasn't something else before starting NADS.

So what I would suggest you to do is try a boost controller (Dawes or Tiillix)+ 3 needle valves. Proven to be a good MAF/Boost control setup.

As you have a Dawes boost controller_Is it a black body type (3bar racing stencilled on it)?
If so suggest you contact Lindsay at Tillix and buy 2 needle valves. Two needles because I assume you already have one needle valve. If not the black body Dawes you can buy Tillix as you have ordered.

Tell us what valves you have and we can go from there and if you are interested in trying Dawes or Tillix + 3 needle valves, contact Lindsay (Tillix) and get him to hold your order as you may not require the Tillix boost controller but do get the 2 needle valves if you already have 1 needle + Dawes(3 barracing)...

Have a read of this thread as linked here and go back thru the posts to get a better understanding of the set up(covers both DI & CRD):

1 Dawes/Tillix + 2 needles, or just 2 needles, or ... 3...