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Discussion Starter · #1 ·
I recently bought a 2006 Nissan Navara Aventura (Manual Diesel) with a YD25DDTi engine. I am now trying to work out all the bugs. I have the same "no power", "black smoke" problems that I have seen in a number of other posts on this forum. I have tried all of the easy fixes and would love some insight into a couple other symptoms I have noted.

What I have done:
I blanked the EGR (which appeared to be intact and working), cleaned the MAF, changed the diesel filter and filled the tank with fresh diesel, changed oil and filter just to be safe.

What I noticed:
Small amounts of oil on top of injectors 1 & 3, No power (cant get anywhere fast and over 60mph is impossible), black smoke on acceleration, standing black oil in pipes from turbo to intercooler and intercooler to intake

The previous owner seems to have bypassed the boost control solenoid and run the vacuum line from the pump directly to the solenoid control valve. If I disconnect the vacuum line while the engine is running the rod goes down and if I reconnect it, the rod returns to the upper position. I have removed and tested the solenoid by applying 12V to the coil and it seems to be faulty. (Probably why the brilliant previous owner bypassed it) My question is what would bypassing the solenoid cause the engine to do? No boost, or boost all the time? I will obviously be attempting to fix this one/ buying a new solenoid but I need to know if this would cause the symptoms I am experiencing.

Also I have removed all 4 injectors and #1 appears to have oil and carbon on the stem. This could be a byproduct of a failing O-ring but the carbon makes me think that the washer failed and exhaust gasses were escaping up into the engine (which would explain the black oil). Thankfully the seats all appear to be clean and undamaged! I have attached a photo of the injectors and am wondering if the carbon deposits on the tips of all four could be caused by the bypassed solenoid giving a rich mixture. Thanks for all your insight and all the help I have already received by reading others posts. Sorry for the 5 paragraph essay and I look forward to hearing your thoughts.
 

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By passing the boost control solenoid means too much boost and poor running. It sounds like it is broken.

Don't worry about oil in the intake, it has come from the crankcase ventilation and is normal.

Not sure about the injectors.
 

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Discussion Starter · #3 ·
Just an update...

Since engine runs smoothly I decided to fix one problem at a time. I cleaned the injectors (exterior), replaced the washers and o-rings and put the cover back on.

Measured some vacuum pressures today and cleaned the boost control solenoid. The coil is OK and the metal clip around the outside is not difficult to pry up and remove. This allows the solenoid to be separated into two pieces and everything inside to be exposed and thoroughly cleaned. I believe I am getting a bit of vertical movement on the valve now.

Vacuum from the pump (at, but before the solenoid) = 26psi
Vacuum at the boost control valve (after the solenoid and hose) = 14psi and increases to 16psi when car reaches 4000 rpm

Noticed today that pipe going from turbo to intercooler does not change at all as engine is revved. Suspecting a problem either with the valve inside the turbo that allows air to bypass the turbine or improper adjustment on the rod which operates this valve.

Car still has slow acceleration, smoke, and acceleration does not increase from 50% to 100% throttle when in 4th-6th (However more black smoke does come out) This indicates that more fuel is being provided but not enough air is reaching the engine to allow for the proper fuel:air ratio. Again, this could be caused by the turbo.

How hard is it to take the turbo out? Any special considerations?
 

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Not a great job taking the turbo off, several studs will snap.

Back to the BCS, is the little actuator pulsing up and down at idle? If not, a sure sign the valve is not working as it should.
 

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I'm interested but not following the vacuum bit - isn't 26psi nearly 1.75x atmospheric pressure?
 

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Discussion Starter · #6 ·
@landmannnn
Not a great thing to hear going in... :shock: The valve rod is moving slightly, barely noticeably. I will put a ruler next to it today and see if I can get an accurate reading relative to the valve itself. I have attached a couple videos showing vacuum operation. Let me know if there is any other way to test what should be happening at the valve. Also there is an adjustment screw? on the valve rod. Any way this adjustment screw is way off and the valve is not opening and closing as it should?
@freemansteve
That is correct. Couldn't find many specs as to what the vacuum should be but the consensus I obtained from this forum is that it should be between 25-30psi or 1.7-2 atm from the pump. Does that sound right to you?

Vacuum before Solenoid
https://youtu.be/_O5aJwMu0UY

Vacuum at Valve
https://youtu.be/VUArye_5PQU
 

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I'm not being contentious, but I was thinking a "perfect vacuum" would be 0 psi, and a "slight vacuum" would be something between 0 psi and 14.5 psi (ie between zero and under 1 atmospheres)....
 

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There is a mix up here with positive pressures with negative pressures.
Positive pressures can be measured in PSI amongst many calibrations.
Negative pressures e.g. partial vacuums can similarly be measured in vacuum inches, usually water or mercury.
26psi positive is no where near 26" vacuum pressure either water or mercury.
If you look at your compound gauge it is able to measure both positive (although not very high 9PSI max) and negative (it has the ability to measure 1 bar), it goes immediately to negative pressure indicating a vacuum, therefore you are comparing to the wrong specs!
 

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@landmannnn
Not a great thing to hear going in...
The valve rod is moving slightly, barely noticeably. I will put a ruler next to it today and see if I can get an accurate reading relative to the valve itself. I have attached a couple videos showing vacuum operation. Let me know if there is any other way to test what should be happening at the valve. Also there is an adjustment screw? on the valve rod. Any way this adjustment screw is way off and the valve is not opening and closing as it should?
@freemansteve
That is correct. Couldn't find many specs as to what the vacuum should be but the consensus I obtained from this forum is that it should be between 25-30psi or 1.7-2 atm from the pump. Does that sound right to you?

Vacuum before Solenoid
https://youtu.be/_O5aJwMu0UY

Vacuum at Valve
https://youtu.be/VUArye_5PQU
The actuator rod should move up and down about once per second, from memory perhaps 5mm.
This rod alters the variable vanes on the turbo, possibly it has seized a bit. If you take the intake hose off with the engine stopped you should be able to see the vane movement by moving the rod.
 

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Remove the turbo vacuum hose from the boost solenoid. Stick it in your mouth and suck on it. The rod should move a fair amount. If it doesn't move at all or very little then it seems your wastegate is shot or VGT vanes are seized depending on the turbo your Nav has(I am not sure about UK models).

If the shaft does move substantially compared with what you are seeing at idle then it does seem likely your boost solenoid is toast or you have a vacuum leak somewhere. Check all the hoses running from the vacuum pump thoroughly as any leak in the system will cause problems. If everything seems in order then bite the bullet and buy the controller. Small price to pay for a happy truck. I've had a broken vacuum hose before (dealer broke it clean off when changing oil filter) and it's definitely truly terrible without boost.
 

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Sound advice, from the description he has a VNT turbo. Actually the original poster is closer to your part of the world than the UK.
 

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Discussion Starter · #12 ·
Thanks for all of the input.
@freemansteve
I have not had much experience with vacuum testing so no hurt feelings here :grin2: The gauges I am using to measure negative pressure are a set of vacuum gauges for balancing street bike carburetors. Also done by measuring negative pressure and comparing the values. My gauges indicate that the measurement is actually in "Vacuum Inches" as clarified by @chris vince (thank you). Therefore converting the values given earlier into atm

26 in Hg = 0.869atm
14-16 in Hg = 0.4679 - 0.5347 atm

according to the online google conversion calculator.
@chris vince
Thanks again for the clarification!
@landmannnn
Rod is definitely not moving that much. Ill have to take another look at that solenoid. Any clue what voltages vs rpm I should expect at the plug for the solenoid? Just want to double check the wiring before getting a new solenoid?
@Born-2-Fish
I removed the vacuum line and did the "manual suction test." The rod moved considerably more that it does at idle. However I then started the engine and after starting connected the line coming from the solenoid to the valve and the rod moved as if I sucked on the line. (meaning it is getting suction at idle) From the video you can see that the suction is present at the valve but at about half the value from before the solenoid.

I will double check all of my vacuum lines and connections now and make sure I didn't miss anything. With murphy's law it cant just be a hose...
 

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If it is the turbo vanes that are gummed up and seized, before you shell out for a new turbo, they do clean up remarkably well with a few doses of strong oven cleaner.
 
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Whilst I'm by no means an expert on the mechanical side of these matters, I had a very similar problem with my truck and having replaced the solenoid and the maf sensor it actually turned out to be a leaking hose. The air intake to boost solenoid line. Whilst I can't guarantee success, I would strongly recommend replacing all the airline hoses connecting to the turbo and boost solenoid to eliminate that as an issue. It can also be worthwhile applying lubricant to the underside of the actuator if the previous owner has had it jammed open and it's not been allowed to move freely for a sustained period of time.
Can't help you with the pressures etc you mentioned so you're obviously way more competent than me mechanically!
Good luck.
 

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Discussion Starter · #15 ·
Just to provide an update/tentatively close this thread;

After a week with a mechanic who seemed to not know his head from his ass (he was on his way to dismantling the catalytic converter) I gave up and decided to take it on myself.

I first looked to remove the turbo where I found that 2 of the 4 bolts which secure the turbo to the manifold had snapped off leaving only the threaded portion in the manifold... The genius who installed the turbo had decided this was better left as is and just left it like that. There were about 4 bolts missing in the two shields that surround the turbo and a leak from the gasket where the oil pipes go into the turbo.

After removing the turbo I also removed the diesel particulate filter (short fat pipe connected between the turbo and exhaust) and used some compressed air to spray the abundant dry carbon out of the filter. There was excessive carbon build up in the turbo as well and that was cleaned thoroughly. The rod from the actuator to the turbo was improperly adjusted both on the rod itself and the stopping bolt that limits that valve position. After reassembling all pieces, removing and replacing broken bolts and missing bolts, I do have boost again. I am still getting only decent low range acceleration (as well as some black smoke) and the rod from the valve is not moving as it should at idle. (Rod does move up when vacuum hose is connected and boost is present: car accelerates well above 2k rpm) However, it seems the main problems were an air-flow restriction caused by the DPF and a possible air leak at the turbo-manifold connection.

Thanks so much for the help and I will let you know if I solve the solenoid problem. Plan on taking my OBDII reader and trying to get a boost pressure reading to see if I can pinpoint the problem.
 

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Just to provide an update/tentatively close this thread;

After a week with a mechanic who seemed to not know his head from his ass (he was on his way to dismantling the catalytic converter) I gave up and decided to take it on myself.

I first looked to remove the turbo where I found that 2 of the 4 bolts which secure the turbo to the manifold had snapped off leaving only the threaded portion in the manifold... The genius who installed the turbo had decided this was better left as is and just left it like that. There were about 4 bolts missing in the two shields that surround the turbo and a leak from the gasket where the oil pipes go into the turbo.

After removing the turbo I also removed the diesel particulate filter (short fat pipe connected between the turbo and exhaust) and used some compressed air to spray the abundant dry carbon out of the filter. There was excessive carbon build up in the turbo as well and that was cleaned thoroughly. The rod from the actuator to the turbo was improperly adjusted both on the rod itself and the stopping bolt that limits that valve position. After reassembling all pieces, removing and replacing broken bolts and missing bolts, I do have boost again. I am still getting only decent low range acceleration (as well as some black smoke) and the rod from the valve is not moving as it should at idle. (Rod does move up when vacuum hose is connected and boost is present: car accelerates well above 2k rpm) However, it seems the main problems were an air-flow restriction caused by the DPF and a possible air leak at the turbo-manifold connection.

Thanks so much for the help and I will let you know if I solve the solenoid problem. Plan on taking my OBDII reader and trying to get a boost pressure reading to see if I can pinpoint the problem.
At least some progress. Still struggling with smoking over here. Thinking of checking the turbo as well

Sent from my D5803 using Tapatalk
 

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Discussion Starter · #18 ·
So I decided to keep the thread alive to keep all the info in one place.

Problem still exists, just not quite as bad with a clean fuel system. Still smoking and no acceleration at low revs in any gear but particularly the high ones (>4)

Put an OBDII reader on it and Intake Manifold Pressure is sitting at 25 in Hg (.847 bar or .836 atm) up to 4500rpm. (This is sitting at idle) I know the turbo is spooling up because I can hear the whine and I have seen the turbine spinning. The fact that the reading stays the same just seems wrong to me. I have tried spraying out the sensor and making sure the vacuum line is hooked up properly from the intercooler and all looks good.

Does anyone have reference values for the ideal pressure readings or if the reading should change dramatically when revs are increased? TIA
 

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So I decided to keep the thread alive to keep all the info in one place.

Problem still exists, just not quite as bad with a clean fuel system. Still smoking and no acceleration at low revs in any gear but particularly the high ones (>4)

Put an OBDII reader on it and Intake Manifold Pressure is sitting at 25 in Hg (.847 bar or .836 atm) up to 4500rpm. (This is sitting at idle) I know the turbo is spooling up because I can hear the whine and I have seen the turbine spinning. The fact that the reading stays the same just seems wrong to me. I have tried spraying out the sensor and making sure the vacuum line is hooked up properly from the intercooler and all looks good.

Does anyone have reference values for the ideal pressure readings or if the reading should change dramatically when revs are increased? TIA
Not sure, I normally show the boost gauge which is a different guage I think. If I am wrong then the boost sensor is broken.
 

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Discussion Starter · #20 ·
OK I'm slowing down a little bit. I have now replaced the MAP sensor (Aka Boost Sensor) as well as the Boost Control Solenoid. When I switch on "high idle" the bar is moving the correct amount. It is not moving a low idle but Im willing to overlook this detail for now.

I watched a bunch of videos on youtube and one of them from West Yorkshire Engine Services (
) focuses on a sound made when one or more injector is going bad. Above 2500 rpm (sometimes over 2000rpm) my Nav is definitely making the "rattling" noise. I will see if I can post a video followup for reference. Its more like an empty engine exhaust sound (coming from the engine) in my opinion but why split hairs lol. With 209,xxx on the clock it seems I am overdue for an injector swap as many people on this forum have them going bad at about 150,xxx.

The unfortunate part is I am located in Zambia, Africa so will have to get new ones from the UK since the only ones available here are secondhand and might be just as bad with a higher price tag (ZMK3000 or just over 300USD!). So I have located the injectors on PF Jones' website and was looking at reconditioned vs new. With the reconditioned refund of 60 pounds for the old injector it brings the total to 120 for a reconditioned injector and 260 for a new one.

So all of that info for two questions.

1. Has anyone else bought reconditioned injectors from PF (or anywhere else for that matter)? They do have a 12mo warranty but it would be a PITA because I would have to ship them back to the UK.

2. What computers has anyone used to program the values into the ECU? I saw @CEKing85 mentioned he used a Delphi DS150E with Autocom. Anyone else had success with these? Looking for the cheapest solution as I have a Bluetooth OBDII dongle but it doesn't support this function so only buying it for this one job.

Thanks for the info, if a new thread is required I will happily move this post but the symptoms still match the above problem so I thought I would try here first. Thanks in advance!
 
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