Help turbo not boosting in 5th gear only???

[Nav1990]

I have a 2003 Navara STR 3.0l ZD30 and for some strange reason recently the ute will not boost in 5th gear. every other gear is fine and she boosts well... i have removed the vac line on the egr actuator and there is a vaccuum there (Meaning the vac pump is good, i have also pumped the brake pedal which went hard with no ignition to ensure the vac line is good), i have also moved the other actuator rod back and form on the opposing end of the turbo housing (unsure of its name) it does not make any unfamiliar noises from the turbo and has always been serviced regularly. any advice on this matter would be much appreciated????? i am pretty technically minded but this has stumped me !!!
i have just changed over vac lines and test run (too no improvement)

I have also checked the neutral position switch with the engine warm button on and once engaging 5th the rpms drop back to normal idle rpms (must be a pass)

however when inspecting below where the neutral position switch comes from the gear stick i noticed that one of the sensors on the gearbox had been damaged and sheered. i traced photos online to see how the wiring went and ended up guessing. the guess wasn't a good one as everytime i engaged the clutch to change gear a clicking sound would be made, i reversed the wires over immediately and this stopped the clicking noise, however the **** ute will still not boost in 5th gear still...

it feels like a dead gear as soon as I'm boosting in 4th then going to 5th it just goes flat to 2000 rpms then steadily climbs (but will not go above 110kph, and when theres a hill i lose speed) i have moved the gear stick left right up down etc when in 5th to see if it will boost, but nothing!!!

the ute is also fitted with a Turbo timer also and the fuel filter has been changed

Any info is greatly appreciated

 

[Old.Tony]

The definitive test for the NPS is to disconnect it. The turbo timer shouldn't affect it.

 

[Nav1990]

Hello old.tony what is the procedure to test the Navara with the neutral position switch removed? Also for clarification which switch is the neutral position switch?

Thanks for the reply mate

 

[Nav1990]

The location of the switch that is?

 

[Rumpig]

If it's not the nps then it sounds like it must be starving for fuel but you would expect it to do it in 4th as well. Bit of a mystery.

 

[Rumpig]

Just unplug it under the car and go for a drive. Separate the plug on the left next to my finger tip.

 

[Oldie]

I get the same problem with my old girl going from 3rd into 4th. slow to pick up. but it only happens when going up an incline or hill.
I had my NP and RL switches replaced just a while back so thinkin the turbo may just be gettin Old like the owner haha
On flat road, I don't have a problem. when towing you certainly notice that you have to hit a certain amount of revs then you can feel the turbo kick in.

 

[Nav1990]

plugged the nav into the dyno tonight and nothing registered on the system scan. so on we went for a drive with the dyno plugged in and my mate reading the running statistics. everything and i mean everything was bang on and there was a little improvement on boost in 5th gear, however not what it used too be.. we watched carefully in every gear to see whether the neutral position switch would remain ON when we selected gears both stationary and when driving, however the switch was working how it should be and switched between ON and OFF as it should... this has really left me clutching straws... what am i missing??????????????????

Cheers old.tony for the pic I believed that to be the switch but wanted too make sure... I'm completely stumped now after te dyno has given the all clear

 

[Old.Tony]

Wasn't my pic, it was Rumpigs (thanks, Rumpig!).

The only things that can affect how the computer allows fuel injection rates/boost to be inhibited are the NPS, clutch switch and I think the handbrake (model dependent). If your NPS is working correctly, check the clutch and handbrake switches.

 

[Nav1990]

Haha cheers rumpig

 

[Nav1990]

Wasn't my pic, it was Rumpigs (thanks, Rumpig!).

The only things that can affect how the computer allows fuel injection rates/boost to be inhibited are the NPS, clutch switch and I think the handbrake (model dependent). If your NPS is working correctly, check the clutch and handbrake switches.

Old.tony

I have had a friend look over the Navara and as I've been driving it for so long I haven't noticed that it seems to lag in all gears, and when going into 5th That's when it' just struggles... I have read into the Dawes valve and adding a turbo boost controller... What will the issue be? you can hear the turbo sucking and feel it sucking from the air filter intake box... However it just seems to over suck and boost early..

Any info is much appreciated

 

[jonney]

maybe its time for a good free flow exhaust system unless you already have one fitted. the str / 2.5 litre with a good 2.75 inch system seems to have no lag in any gear from what i have gathered with my sons str. also how good is your inlet manifold i regards to soot build ? egr blocked ? the engine loves to breath, if it has restrictions it wont breath properly as you may know.

 

[Old.Tony]

The STR has a solid path from turbocharger to intake manifold so lag is minimised - unless someone's installed a FMIC.

I wonder about the wastegate as well. Is it sealing? Do you see any soot expelling from it?

 

[Rumpig]

It could be the MAP sensor isn't working, unplug it and go for a drive, if you don't notice any difference it may not be working, check the hose going to it for leaks too. It's the fitting with the grey plug mounted on the intake pipe.

 

[Nav1990]

It could be the MAP sensor isn't working, unplug it and go for a drive, if you don't notice any difference it may not be working, check the hose going to it for leaks too. It's the fitting with the grey plug mounted on the intake pipe.

I've seen videos and images of the maf sensor however the one on my Navara is just a sensor connector, correct? I thought that they had a circuit/air flow reader that you could pull out and clean? So if the maf sensor is knackered would it require changing both the plug in connector with wires and the socket on the intake mount?

Cheers

 

[Nav1990]

The STR has a solid path from turbocharger to intake manifold so lag is minimised - unless someone's installed a FMIC.

I wonder about the wastegate as well. Is it sealing? Do you see any soot expelling from it?

Sorry to sound green but what is FMIC? The waste gate doesn't seem to have much soot around at all... Does the actuator rod on the waste gate pull back and forth to open or does it only open when releasing pressure? Turbos are not my fortay so excuse all the green questions..cheers

 

[Nav1990]

maybe its time for a good free flow exhaust system unless you already have one fitted. the str / 2.5 litre with a good 2.75 inch system seems to have no lag in any gear from what i have gathered with my sons str. also how good is your inlet manifold i regards to soot build ? egr blocked ? the engine loves to breath, if it has restrictions it wont breath properly as you may know.

The egr is not blocked yet... On inspection a few days back with manifold tubing off it only had minor oil in the housing, not much soot... I am due to take apart the 2 way manifold, is this a major job?

 

[bods]

Fmic is front mount intercooler, zd30s don't have a maf sensor, only a map sensor as mentioned above. The turbo wastegate only opens when the set boost pressure is reached. I believe around 16psi for the zd30. You won't be able to move it by hand, if you can, the actuator isn't working properly and will be releasing boost too early. The easiest way to confirm is with a boost gauge, it should reach and hold a steady 16ish psi under full load. If it is below that then you have a wastegate problem.