3.0 TDI with erratic loss of boost

[Tony]

Hi guys, I am a new kid on the block! I just bought my 2003 3.0 TDI GRX a year and a half ago (eventually!) at 118 000 km's. I have had a number of little problems over this time, but since December I have been experiencing a strange problem where the vehicle suddenly loses power when traveling at a very sedate 100 - 120 km/h. Pushing the accelerator flat has absolutely no effect, but if I ease off gently on the gas and then depress the pedal again, the power is back with a boost and all is ok - for a while. This can occur continuously every minute, or less frequently. When I contacted my mechanic, he suggested water in the diesel, I went to Nissan PE and we removed and replaced the diesel filter, and found a small trace of water in the diesel from the old filter, however my problem continued until about 300km later when I needed to fill up and could only find 500ppm diesel (up to this point I had used 3 tankfulls of 50ppm only) immediately my problem dissappeared. I just took a trip down to Clarens last weekend, filled up with 50ppm and I have the same problem! About a month ago I had a Dastech chip installed and a decat, and Steve from RG Diesel said he was having trouble setting the oxygen sensor. Could there be a connection? I have been advised by my mechanic to go to Nissan and to have a full diagnostic done and then to take the results back to him to try and resolve the issue. If anyone can give some advice as to what it could be that is causing this I would be really grateful.

[KOOS BEST]

Hi Tony, extracts from the refence document, off load the doc its very important for ZD30Nissan Patrol Reference Document
Page 12 of 112
TEST IF YOUR VEHICLE IS AFFECTED BY OVER BOOST – HOW TO
To test if your vehicle is having the over boost issue carry out the following test;
• Find a nice flat piece of highway where you can coast the vehicle at a set speed without
changing speed or RPM while driving i.e. moving your foot up and down on the
accelerator.
• Get the vehicle to around 100-110 klms, not your corrected version for bigger tyres etc.
This is dependant on your vehicle; a manual GU4 sits around 2600 RPM at about this
speed. Drop gears but keep in a higher gear so that slight foot movements are minimally
registered. 4th or 5th gears are preferred.
• The important thing is to keep the vehicle at around 2600-2700 RPM.
• Coast at this for as long as you can and see if you can feel an engine twitch (bit like
being hit by a slight side wind, can take anywhere between 20-60 seconds) or if you have
a boost gauge watch the boost go to its maximum level and feel for the same twitch.
• If you feel a twitch great, don’t take your foot off the accelerator, as doing this resets
the ECU and it will happily adjust itself and lose the error. Slowly accelerate and if you
foot goes all the way to the floor with no acceleration you have just experienced a
Nissan boost safety feature, by design.
• If you have a boost gauge, on mine the boost dropped to 15PSI for about a second then to
10PSi, then to 4PSI and stayed there with no acceleration possible, foot to the floor
staying at speed.
• If you don’t feel a twitch keep coasting for about a minute then slowly accelerate if you
foot goes all the way to the floor with no acceleration you have the issue.
This Nissan designed feature is to make sure your engine does not stay at boost for long periods
of time therefore causing damage to the engine, it is an over boost safety feature that does not
throw an engine management code.
HOW I TESTED MY OWN VEHICLE
All testing was carried out on my manual Nissan Patrol Y61 ZD30TD 2005 GU4 model, build date
is June 2005, 3” mandrel bent exhaust with ceramic coated dump pipe, hi-flow CAT and vortex
muffler. I also had access to 2 other 2005 model GU4 experiencing the same issues after EGR
blocking, both with 3” exhausts. It seems that the GU4’s may not be as tolerant of modifications
as the Series 3, could be different ECU’s, more boost, new ECU code introduced, could be many
variables?
When increasing your exhaust diameter, thereby improving gas flow, or blocking the EGR and
redirecting the additional exhaust gas flow toward the turbo it will cause the turbo to spin
faster thereby giving better low down performance and faster Turbo spool up which can greatly
reduce Turbo lag, and is seen as a plus for drivability, but this also increases boost.
In the below I used the above method to test, I also tested each phase over a number of days
with a mixture of highway and around town driving. I was advised by two independent sources
that by performing the test method above my maximum boost should have been around 10-11
PSI so this is what I set the boost around (I could not find a standard same year unmodified
vehicle with boost gauge to test on).
• EGR unblocked, tested, boost was too high at around 18 PSI, so it errored as expected.
• Screwed the VNT 3/4 a turn to drop the boost to around 10-11 PSI, tested, at this point
of the test the vehicle was far more drivable even revved quicker to the higher RPMs
(3500-4000) than it had for quite a while. The engine did not work as hard and gear
Nissan Patrol Reference Document
Page 13
changes were smoother. After driving for a short period the boost would “creep up” by a
PSI or two and settle around 13-14 PSI.
• I then blocked the EGR and turned the VNT a further 1/4 a turn, tested, noticed the
boost back up around 16 PSI. So blocking the EGR increased the boost by about 5-6 PSI.
Driving around town between gear changes it felt like there was a restriction in the
engine so when you changed gears the RPM dropped quite quickly and made changing
gears jerky.
• I then turned the VNT again so that it is now 1 1/4 turn in total and the boost is now
normally back around 10-11 PSI. The vehicle is far more drivable at this level and it still
has plenty of pulling power down the highway. What it did was cause a type of power
band at around 2000 RPM that would make the car take off when you hit the accelerator
for overtaking etc and the boost stayed low. It is very easy too start at 2000 RPM and get
the car to over 4000RPM easily without feeling any engine restriction. However one slight
side affect was the loss of some, not much but noticeable, torque down lower. The
owners of some cars I have adjusted want to leave it this way and not re-adjust as I have
done below. If you drive a car set up like this you would understand why, you can be
cruising at 100 klms and put your foot down to overtake and the car just takes off, even
while you are towing, with no over boosting of the engine.
• After the above testing, and a few months, I re-installed my Steinbauer Diesel
performance chip. What this did was change the way the fuel is delivered to the engine
and gave it more pulling power down low. One of the side effects of installing a chip is
that it will make the engine run slightly hotter the more the chip is turned up the more
fuel, so the hotter it gets. This can also be detrimental to your engine if you do not keep
and eye on it.
• Now here’s a catch, the turbo is also responsible for cooling the combustion
temperatures in the engine. So I simply re-adjusted the turbo VNT screw back 1/8th of a
turn to slightly increase the boost to around 14 PSI while cruising on the highway. The
VNT screw is now set at 1 1/8 of a turn in total. This had the effect of dropping the
temperatures by approx 25 deg C, and gave me back some lower down torque. The
engine now has a more even power band right through the RPM range. BUT guess what,
while cruising down the highway the engine now over boost errors as it did previously.
• So final adjustment was to turn the screw back to its 1 1/4 setting to stop the over boost
error. So you can asee that only a slight 3-4mm turn of the screw can have such an
effect.
After each test I reset the ECU by disconnecting the battery(s) for 20 minutes. Make sure you
save your trip meter reading or you will lose them. This reset allows the vehicle to start back at
factory defaults and re-learn its engine set up accordingly. As a matter of course I will do this
every time my vehicle has been serviced at a dealer and it always performs smoother and
quieter than when I receive it.
IN SUMMARY
Even performing the above adjustments does not limit your maximum boost to 10-11 PSI.
Remember that at all times your boost and fuel are being determined by the ECU and it will
decide how much boost you are going to get when you need it.
When I drive around town and accelerate down the street I still get boost readings up to and
over 20 PSI with the occasional higher spike just like normal, as I should as it is a design
characteristic of the Turbo (see Glossary on VGT).
What the above does is bring the mechanical/vacuum controlled boost VNT actuator setting
down to its normal designed threshold so that while coasting along the highway you don’t over
boost your engine and cause other issues along the way, like a leaky intercooler due to higher
than normal boosts over long periods of time, or a blown engine because your MAF has failed
and the over boost just helps it fail that much sooner.
The best way to protect your engine is as a separate section in the document. So get to it, give
your engine a test and see if it happens.
Just remember, these are a great engine and Nissan to its credit has been trying to engineer out
any issues over time, in my own opinion, with the mix of power and economy and the fact that
it needs to pull a 2500 kg vehicle around it does a great job.
If you modify your exhaust, block the EGR or both you will cause the engine to over boost, it
may not boost high enough to throw a code, or even to error all the time, but it definitely will
be boosting higher than designed

[Tony]

Thanks Koos, for your very thorough response. At least this is not a major problem that will cause me sleepless nights, or leave me stranded on the side of the road. Nice to have this kind of support from fellow Patrol Manne!

I bought my Patrol firstly because it has been the one vehicle that has had massive appeal to me, I fell in love years ago and have wanted one forever - but more importantly it stands for everything i've always wanted to do one day, in terms of overlanding and general long distance cruising - with awesome offroading ability. So far I have upgraded the suspension with an Ironman kit, installed a Safari Snorkel and recently chipped and removed the catalytic converter. This was recommended by the guys at Rob Green. Roofrack and Bushbar will be next - if anyone has pics of their bars or roofracks I would love to see how they look.

[SCUBA Patrol]

Hi,

I'm down in PE and contacted Madman about their "meter". They do not have a kit made up for the NIssan patrol 3.0l. are their any of you okes in Pretoria that would take the time and visit them with your patrol in order for them to build-up a kit for the patrol? I realy would like to fit a Madman system to my 2006 3.0l Patrol!

Pleazzzz

[Pieter du Toit]

Hi Scuba,

You don't need a kit from Madman - you can buy just the madman meter - all the other items you can buy loose from most places.

See my post here http://www.patrol4x4.co.za/viewtopic.php?f=53&t=363 about the egt installation.

Also see my post here http://www.patrol4x4.co.za/viewtopic.php?f=53&t=445 about the boost installation.

Hope this helps - but shout if it does'nt because then we can see what we can do here from CT!!

Regards

[Langman]

Hi Tony

Have you managed to get to the bottom of your "little" problem? I am curious to know if this started, gradually or just suddenly...reason is I also have a 2003 3.0 Di GRX however mine has slightly higher mileage and I don't know if my problem could be linked to what you experienced. Same as you I am new on the block but even worse is that I was previously a petrol head meaning I have no clue what to look and listen for as diesel 'tell tale' problems and signs. What I noticed is that also between 100 - 120 it feels sometimes as if there is a lack of power. Not that bad but it's there and if you accelerate past this it seems to go away. It also does not always happen??? It almost feels likea a petrol engine losing fire due to a plug that's about to go. Was this the same you experienced? If anyone else out there can give me advise I am all ears...hopefully it is something small.

[Izak]

Hello Scuba

I have been contemplating putting in a Madman in my Patrol. The kit that you talk about, what does that mean? I stay in Alberton but have regular meetings in Pretoria. I can do because I want one as well.

Izak

[Tony]

Hey Langman, sorry I have not responded, just not had time to play on the old pc for some time. My problem occurred overnight! We drove down to Ballito and spent a week there, then filled up with 50ppm at the local BP, and two hours later on the way down the coast to Transkei I suddenly felt the (like a little shudder almost) and it felt like the life had gone out of the motor. I only discovered later that lifting my foot off the accelerator, and easing it down again she surged forward and all was back to normal - for a short while, that is. This continued sometimes at 5min intervals or other times at much longer intervals. Rob Green were'nt happy with the boost control, and after a second visit (after chipping & decat ing), they made the sudden boost which I was experiencing (I thought this was normal on all 30 TDI's) a lot more gentle - in other words I now need to ease my foot down somewhat more to experience that extra oomph. I must say that I did come to like the sudden gush of power that I had before, and it has taken a little getting used to with less. I do however find the car more driveable in town, and needless to say my problem has been resolved so it was obviously an overboost error that was being experienced.

[JG Shields]

Tony,

I had exactly the same problem with my ZD30 engine in the Patrol. Al the kings horses and all the kings men could not put the problem to bed...that's Nissan I am talking about. In my case it was the "boost" sensor, situated in the front of the intercooler. I replaced it and all was good again. The sensor is a mechanical/electric sensor and goes faulty after some time, mainly because of dirt in the intercooler. It gives an inaccurate reading (over reads the boost) to the ECU which in turn puts the car in limp mode. When releasing the throttle, the ECU resets on the lower boost reading and the car goes strong again.

Good luck!

[chipompi]

Hi, after having read the posts on the ausie website I decided to block my EGR, i did find that i had more grunt until i turned down my turbo as recommended to stop the over boost but now find that the trol is a bit slugish low down, iam thinking of putting my settings back to where they were.

what i would like to know is if being at altitude effects the boost, i live at 3600feet and drive like an old man and dont drive at excessive speeds or tow anything