Top end power problem

[JAWZ]

Ive got a 2005 Navara D22 str thats having issues with power at the top end of its range. Its seems to struggle to get air and when driving up hills on the freeway i usually end up down gearing a few times. On the flat she cruises along at 100-110 no worries but throw a hill in and she's struggling where the turbo kicks in.
At my service the mechanic said my turbo needs replacing as the issue but he just looked at it and didn't inspect it at all.

Im prepared to buy an aftermarket turbo and just swap it out if need be myself just wondered what the brains trust here thought or have experienced?
Cheers Guys

 

[tweak'e]

i doubt very much its the turbo.

but really need to know what exact rpm your talking about.
i'm more inclined to think its a fuel problem. but there can be other things.

 

[JAWZ]

Seems to kick in at 2250rpm.
Ive changed out all my filters twice now as i thought the same thing with it possibly being a fuel issue.

 

[Rabbid-chop]

I was going to say filters. My 2004 was like that from new, seemed to open up a bit more after about 150,000 km. Exhaust, prefilter delete and egr/swirl mod made a bit of difference. Chip made a massive difference. Running a gt2554r now and a rumpig tune, goes like the farking clappers, lol. Maybe chuck a cheap boost gauge on just for shits and giggles and let us know what she's making - it think mine was about 13psi stock at full noise.
Ive got two forefront prefilter delete pipes sitting here if you want one.

 

[tweak'e]

Seems to kick in at 2250rpm.

first thing is that is mid range not top end.

can you find another one to drive and compare?

so the question is, is what you are describing normal or a fault?

these tend to have a small top end power band. generally 3000 to 3500 rpm.
on the hills they need to be doing around 3000rpm.
they are under fueled in the low rpm. down around 2000 rpm power drops right off.

 

[JAWZ]

Ok I understand what your saying but it never used to do this.
You can feel it struggling to get going and I've been down to 2nd gear in some hills out west. On the flat she's fine but when you put your foot down she struggles enormously.

 

[tweak'e]

i forgot the simplest, the NPS. look up the threads on the neutral position switch. unplug it and see if it fixes it.

 

[Old.Tony]

^ as per Tweak'e. Diesel engines don't use a butterfly to control the amount of air entering the engine - they get a full gulp every time. The three main reasons for a loss of power are underfuelling, failing turbocharger or a dodgy NPS. Work on the last one first - unplug it and take the car for a drive.

 

[tweak'e]

Diesel engines don't use a butterfly to control the amount of air entering the engine -

actually they do, especially anything common rail. tho its for emission control.
quite possible to get jammed intake butterflies.
with zd30 that would show up as loss of power with black smoke out the exhaust.

 

[JAWZ]

Thanks a lot guys I'll give that a whirl and get back to you.

 

[Bax84]

Check for a boost leak as well.

I came back from a trip a year or so ago, noticed it was incredibly sluggish up hills, could hear the turbo powering along and it was fine along the flat. Opened the bonnet when I got home and noticed I had a pipe off. Connected it back up, boost again, no dramas.

 

[Horatius]

Had a problem once very similar to what you describe. On the freeway/highway put the foot down to go up a bit of an incline and no power available, having to go back to 4th gear etc. Arrived (wrongly) at the conclusion it was the turbo. When I double checked everything, found a loose plug connection at the boost sensor. It was my own fault too, I had it unplugged some time before this and didn't put it back on properly, must have vibrated loose.

ps. Assuming there are no boost leaks, wouldn't hurt to unplug it and take it for a drive. If there is no difference, that will likely be the problem. Only a suggestion. Afaik (which isn't much and could be wrong lol) if it isn't sensing the turbo trying to boost it will affect the fuel delivery.