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2011 YD25 Navara
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Discussion Starter · #1 ·
I own a 2011 D40 with a YD25 engine with a 6 speed manual transmission.
I have been a long time lurker of this website and decided to make an account to see if anyone can help me or maybe I help someone.
I am having some issues with lack of power at low RPMs and also at high RPMs. When taking off in 1st gear, the truck is sluggish and requires a bit of throttle to get her moving.
At higher RPMs under constant throttle the boost peaks at ~20psi before dropping down to 15 sometimes 17 rapidly, where it stays. I can hear the turbo adjust the vanes and I get a noticeable drop in power.
I have scanned the vehicle and get no trouble codes. I have also attached a picture of my OBDs recording of one said incident.
For clarity, I had the turbo rebuilt this year because of faulty seals, I have cleaned the MAF, Throttle Body and replaced all (hopefully) of the vacuum hoses.
I guess my question is whether or not this behaviour is normal.
I also get a bit of smoke out the exhaust at these higher RPMs

Glad to be involved in the community!


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Discussion Starter · #3 ·
Welcome along. It's just a couple of degrees here, so a bit jealous of you right now in the Caribbean.

Your graphs look spot on.

First check, is the fuel filter reasonably new?
Always worth running some injector cleaner through the tank of that hasn't been done recently.

You shouldn't get any smoke, the fact you are means that something isn't quite right.
I would next double check all the intake hoses for lose connections and splits.
Thank you for the reply. Yes you can have some of our heat. It’s scorching hot the past week.

I have run some diesel treatment to see if it would help but to no avail. I will try some injector cleaner and double check the hoses.
will get back to you soon. Thanks again!
 

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Discussion Starter · #5 ·
Hello again,
So I have completely run through a full tank with the injector cleaner but with no luck. I have also double checked the hoses. The symptoms are the same as before. However i have noticed that the truck will occasionally boost past 20psi up to 25 and hold it there. This usually only happens on first acceleration in 3rd gear after a cold start. After which it will go back to hitting 20 and dropping to 15.
This leads me to my question.
You need diesel and air in the cylinders for combustion. How does the truck know/monitor/regulate the mixture in the cylinder? I have a feeling one of the parameters are not correct. It could be external like a faulty BCS as Daz said.
I feel like understanding this would help me trouble shoot
Thanks again for the time guys!
 

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Discussion Starter · #7 ·
You don't have a boost control solenoid, the boost is directly controlled by the ECU.

Taking the intake of the turbo you should be able to feel if the vanes are free to move, it does sound like they are sticking.
Good day,
Apologies for the late response.
I may be using the incorrect name for the part. But here it is in picture form.
The vanes don’t seem to be sticking.

A new issue has arrived as well. Occasionally I will only get to 10lbs of boost before dropping off to 5. Majority of the time it performs as described in the original post.

Would the boost reach 20 at all if the vanes were sticking?

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You don't have a boost control solenoid, the boost is directly controlled by the ECU.

Taking the intake of the turbo you should be able to feel if the vanes are free to move, it does sound like they are sticking.
 

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Discussion Starter · #8 ·
I have also noticed that occasionally I get a hissing noise from what seems like the brake booster. That goes away when the break pedal is pressed. I attached a vacuum pump to the booster but it wont hold pressure past 15inHg. Could this be the issue? As the two systems share the same vacuum pump?
 
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