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Diesel Flat Spot

7K views 23 replies 11 participants last post by  A.J 
#1 ·
G'day Guys,

I'm new to this site. I just purchased an 05 STS Patrol. Its the 3.0 with auto transmission. Has three inch lift, 3 inch exhaust and DP chip. Problem is under heavy acceleration at 80-110kph i lose all power. If i take my foot off the pedal and reapply i regain accerleration. Took it to local Nissan they plugged it in and tell me everythings fine. This has happened on 5 occassions and I have no idea what is causing it. Any suggestions?

Cheers A.J
 
#2 ·
A.J Welcome to the forum and congrats on the new troll.... Pics please

anyway sounds like you are over boosting and going into limp mod. Taking your foot of the gas and reapplying it is the temp solution while wheeling.
Have a read of the reference document it will help you heaps
http://www.patrol4x4.com/forum/niss...ference-document-zd30-owners-look-here-31418/

also have you got the NADS( Nissan anti detonation system) in your troll
 
#3 ·
Cheers mate. I'm going to take a few pics tomorrow and upload. Long story short is i bought the car from a dealer in Vic. It was one owner, with 108kms on the clock and a fair few mods. Steel bull bar, spotties, snorkel, rear camping light, power to back for fridge, 8 inch fan on intercooler etc aswell as exhaust and lift as i mentioned earlier. I'm still learning my way around the beast and trying to ID what it does and doesnt have. Exactly whats involved in the NADS? Or what are the most basic things i should do to ensure she doesn't die anytime soon?
 
#4 ·
NADS are
Dawes and Needle valve to remove control of the turbo from the ECU or just a dawes to prevent over boosting... again ther are a few methods... look up Chaz or whitie on here... Geeyoutoo... Paul helm... all are very good with this stuff and heaps of other great ideas.
Nissan Patrol Turbo Boost Adjust Kit.
and the Dawes from here
TDi Boost Controller

Catch Can to prevent oily mist from entering back into your intake and contaminating the MAF(Mass Air flow) There are many types of comercially available catch cans people use and you can make your own too
Block the EGR... yours may already be blocked but you need to check this

Boost and EGT gauge to monitor your engines egsaust temp and boost.

These would be the most important things to do. In fact these mods saved my engine just recently when a vacume hose leak occured and my ERT's went through the roof. Because I could see it happening I ajusted my driving style and got it hoem and quick fix. There are plent of threads on here. Just use the search function.
Once you have read the refernce document it will give you a better understnding and more intermit knowledge about the workings of your troll.
 
#10 ·
Cost of NADS plus Boost and EGT guage?

Does anyone have a ball park figure of what having NADS plus Boost and EGT guage installed will set me back? I know it will vary state to state and mechanic to mechanic but i'm not overly mechanically skilled so wont attempt any of it myself?

NADS are
Dawes and Needle valve to remove control of the turbo from the ECU or just a dawes to prevent over boosting... again ther are a few methods... look up Chaz or whitie on here... Geeyoutoo... Paul helm... all are very good with this stuff and heaps of other great ideas.
Nissan Patrol Turbo Boost Adjust Kit.
and the Dawes from here
TDi Boost Controller

Catch Can to prevent oily mist from entering back into your intake and contaminating the MAF(Mass Air flow) There are many types of comercially available catch cans people use and you can make your own too
Block the EGR... yours may already be blocked but you need to check this

Boost and EGT gauge to monitor your engines egsaust temp and boost.

These would be the most important things to do. In fact these mods saved my engine just recently when a vacume hose leak occured and my ERT's went through the roof. Because I could see it happening I ajusted my driving style and got it hoem and quick fix. There are plent of threads on here. Just use the search function.
Once you have read the refernce document it will give you a better understnding and more intermit knowledge about the workings of your troll.
 
#13 ·
Does anyone have a ball park figure of what having NADS plus Boost and EGT guage installed will set me back? I know it will vary state to state and mechanic to mechanic but i'm not overly mechanically skilled so wont attempt any of it myself?
Why don't you drop a PM to Chaz since he is in your neck of the woods, I'm sure he will give you a helping hand in understanding whats necessary, pricing & maybe if your nice he weill assist you in installing some of the NADS.

By doing the mods with the assistance of a content expert, you will learn so much more & have a better understanding of the ZD30, yet alone more confidence in the motor.
 
#14 ·
AJ. I'm one of those dodgy backyard style blokes, I fitted a catch can to my truck, blocked the EGR and did the dawes myself... yet to attempt the Needle Valve (gotto PM Helmsy and arrange some Beers)

If you are ok on the spanners you shouldn't have any trouble doing all that with the info on this forum. If you get stuck, ask the experts... they're always keen to help a fellow Patrol owner out.

$690 for an accelerator assembly... that's as good as robbery. It's too bad the local Nissan dealer tells me I have to buy the whole unit and the spares shop tells me they can order in the electronic parts for MUCH cheaper. At least it was covered by Warranty.
 
#15 ·
I dont understand how them replacing the acc assembly would in any way help the overboosting unless it was sending the wrong voltage??
As far as the NADS goes all is fairly easily and we are all here for guidance. The only thing you may get stuck on is the pyro, an exhaust shop can weld the bung in if you take the dump pipe. I am a fitter and plumber by trade and have spent alot of time working on cars, the thing is if YOU do it, and something happens it will be like" Oh I know what it is " and rectify quickly, if someone else does stuff on your car and it plays up, you will be in the dark.
Im not saying rip the motor out and rebuild it, just none of its too hard if you have the right info.
cheers
Zappa
 
#17 ·
Still going into flat spot/limp mode!!!

I bought the car from a dealership a month and a half ago; therefore it’s still under second hand statutory warrantee.
I have noticed between 80 and 100kph accelerating uphill I lose all power and until I release accelerator and reapply pressure I have no power.
I took the car to Nissan; they tested it and told me the wrong voltage was going through the accelerator. Therefore they replaced the accelerator assembly and problem fixed.... afraid not!
Took it out to Dorado Downs earlier this week, reached the flat spot 7 times on the way there whilst on freeway between 80-110kph climbing up hill. Took it back to Nissan and they can’t fault it apart from telling me there are some discrepancies in the air flow readings? Indicating a possible problem with the airflow meter. Nissan can’t guarantee replacing the airflow meter will fix the problem therefore the caryard I purchased it from won’t pay for the repairs.
I picked up the car this afternoon and hit the flat spot on the 10km trip home......
Does anyone have any suggestions?
 
#20 ·
Turn the DP chip to minimum setting or take it out.
I deal with about 3-4 of these problems a week.

The DP chip on minimum setting is only slightly to rich for a 3L. So EGT's are still in the relatively safe zone.
On medium to maximum they are far to rich.

Let us know how this goes.

P.s Dont play with the VNT yet, it wasnt a problem standard and should not be a problem now.
I have seen 3L with faulty air flow meters come in running 28-30psi of boost, and they didnt cut even at that level.
Adjusting this may help the problem, but it will only be a band aid, not a solution.
 
#21 ·
P.s Dont play with the VNT yet, it wasnt a problem standard and should not be a problem now.
The problem is that it’s NOT standard after fitting a 3” exhaust system. We see plenty of these engines over boost after having large exhausts fitted, but I agree that lowering the DP setting would be worth a try because it’s less invasive and easier to do. However, the DP alters the signals to the IP after the ECU and I can’t see how the ECU can possibly detect a rich mixture condition.

An over boosting issue may just be caused by a large spike due to aggressive spooling thanks to the exhaust and this is one of the few causes of limp mode without throwing a code or MIL that is easily reset by closing the throttle.
 
#22 ·
Apparently the Troll doesnt have a DPchip according to Nissan. I know the previous owner had one on it, as i spoke with the 4WD specialist who serviced the car, however when i went looking for it I couldn't locate it. I'm led to believe that the DP will be connected to the ECU which on a 05 STS should be up under the dash?? Having never viewed it myself i don't know if previous owner took it out, or one of the two caryards it's been to may have knocked it off (I have seen this occur before). When i asked Nissan to confirm if there was a chip there they told me it was too hard to know without ripping the dash out however they didnt think so as it would interfere with the readings when plugged it in for diagnostics, which didnt appear to be happening.
 
#23 ·
A.J,

On your model the DP Chip is wired directly into the fuel pump loom. Later CRD DP Chips were a plug in setup, but still connected under the bonnet. The only Chip/Module that plugs directly into the ECU was the Safari DTronic, which is no longer available. If your car ever had a DP Chip, you should be able to see where it was spliced into the fuel pump loom.
 
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