Boost coming later in the rev range.

[YCJCYASATB]

I have a Ti550. Recently, my performance has reduced in the 1500 - 2000 rpm range. Inclines that used to be handled between 1500 to 1700rpm, have been causing a drop in gear to bring the engine at or above 2000rpm. Where it used to gather steam from 1500 and be pulling hard by 1850 or so has now moved up the rev range by 500rpm.

I use an app on my phone to monitor boost pressure among other things. It still produces 255kpa(absolute), but not like it used to and for a very narrow band. It’s not throwing any codes.

I am thinking along the lines of possible causes, being;
Boost actuator,
Swelling charged air hoses,
Leaking intercooler end tanks,
Down to the turbo being on the way out,
EGR sticking open slightly &
Intake being restricted by soot build up.

I have had a look trying to find a vacuum leak, couldn’t find one.
Just thought I would ask, with the hope that someone else has had the same or very similar issue?
Also seems to be blowing a fair amount of black smoke.
Thanks, Evan.

 

[Old.Tony]

That's not a bad list.

You'll find boost leaks fairly easily, there will be black oily streaks coming out of the leak.

Expanding hoses produces lag but a return to normal power fairly shortly after as the expanded hose fills with pressurised air. Silicone piping may help, like this one:

https://plazmaman.com/product/550-navara-high-flow-air-intake-hose/
but that's $ to invest and should be done once you're sure this is your problem.

EGR: block it and see. There's a chance you'll trigger a Check Engine Light so you may have to take this back out, but you'll at least know where the problem's coming from (this saves you from replacing the EGR valve and not solving the problem).

Worn turbo: not so easy to check on the 550, but if its bearings are failing, there's a very good chance the turbo's been shedding metallic particles. Remove any of the hosing from the turbo to the intercooler and wipe your finger on the inside. Now examine the residue under a bright light - there should not be any shiny flecks in it. If there are, you'll be shopping for a new turbocharger.

Boost actuator (control solenoid): not a common "sorta working sorta not" item. Usually it's a complete fail. Test it by connecting the vacuum pump directly to the turbocharger and take it for a drive: try to do it in such a way that you don't have to back off the throttle rapidly, overboost could pop a hose off. Return the car to normal once you've tried this, you'll know fairly quickly if it's had an effect. If the BCS has failed, you could either try a replacement or switch to something different, like a Dawes or Tillix valve. These work, but at the expense of some fiddling and a turbo that is more reactive than the ECU which works a little quicker.

Black smoke is a sure sign of slightly excessive fuel (which also means less air than required). "Air" meaning oxygen - exhaust gas is not air - so you're right to suspect the EGR valve as well. Try cleaning the MAFS (not sure where this is on the 550 engine) but ONLY use spray electrical cleaner (or MAFS cleaner, same stuff), do not EVER touch the innards of the MAFS, it is very fragile.

You might also consider running a bottle of injector cleaner through a tank of fuel - that stuff can't hurt.

 

[YCJCYASATB]

That's not a bad list.

You'll find boost leaks fairly easily, there will be black oily streaks coming out of the leak.

Expanding hoses produces lag but a return to normal power fairly shortly after as the expanded hose fills with pressurised air. Silicone piping may help, like this one:

https://plazmaman.com/product/550-navara-high-flow-air-intake-hose/
but that's $ to invest and should be done once you're sure this is your problem.

EGR: block it and see. There's a chance you'll trigger a Check Engine Light so you may have to take this back out, but you'll at least know where the problem's coming from (this saves you from replacing the EGR valve and not solving the problem).

Worn turbo: not so easy to check on the 550, but if its bearings are failing, there's a very good chance the turbo's been shedding metallic particles. Remove any of the hosing from the turbo to the intercooler and wipe your finger on the inside. Now examine the residue under a bright light - there should not be any shiny flecks in it. If there are, you'll be shopping for a new turbocharger.

Boost actuator (control solenoid): not a common "sorta working sorta not" item. Usually it's a complete fail. Test it by connecting the vacuum pump directly to the turbocharger and take it for a drive: try to do it in such a way that you don't have to back off the throttle rapidly, overboost could pop a hose off. Return the car to normal once you've tried this, you'll know fairly quickly if it's had an effect. If the BCS has failed, you could either try a replacement or switch to something different, like a Dawes or Tillix valve. These work, but at the expense of some fiddling and a turbo that is more reactive than the ECU which works a little quicker.

Black smoke is a sure sign of slightly excessive fuel (which also means less air than required). "Air" meaning oxygen - exhaust gas is not air - so you're right to suspect the EGR valve as well. Try cleaning the MAFS (not sure where this is on the 550 engine) but ONLY use spray electrical cleaner (or MAFS cleaner, same stuff), do not EVER touch the innards of the MAFS, it is very fragile.

You might also consider running a bottle of injector cleaner through a tank of fuel - that stuff can't hurt.

Thanks for the reply.

I have taken a while to get back as I have been working 12+ hour days. By the time I get home I just want to switch off.

Well the other morning after joining the highway, I was overtaking a car up a hill and it went into limp mode. Pulled over, checked the code P2206 from memory. Anyway boost not reaching the set point in time. Cleared the code and continued to work without any further issues.
Anyway, to avoid a drawn out story. I finally checked my MAF. It was filthy. Cleaned it with contact cleaner and it’s back to its normal self.

The black smoke has reduced dramatically as well. I wasn’t expecting it to be such an easy fix.
Thanks for the suggestion of the MAF.

 

[Olpha]

I have just had some issues of a similar nature with not pulling at low revs and then coming on stronger above 2500 rpm and going really well at 3000 rpm.
The next thing that showed up was a deep resonating through the exhaust at even travel at lower revs. Then started hearing "hunting" at idle although no change in revs.
I pinned it down to being something not allowing the geometry in the turbo to work properly but kept monitoring it until something registered in the fault codes. I didn't have to wait long. A short run with a box trailer up a gentle incline made it de-rate and spit a (pending) P2263 code Turbocharger System. I was able to simply shut it off for 60 seconds and it would reset, but it soon got a lot worse.
I was brave enough to simply order a new one at $275 (genuine Nissan but not from Nissan) and have since fitted it and it is going very nicely now. Added bonus, it is using noticeably less fuel.
One thing I did while changing the unit out was to start the car and then simply take the vacuum hoses off and feel for vacuum from the pump side and once I knew that was ok I placed the ends of the hoses together to test the mechanism on the turbo. Bingo. Instant difference in sound down the exhaust. I also ran the multimeter on the old and new and according to the workshop manuals there was nothing wrong with the old unit. My bush mechanics tells me there is because it's working like a bloody dream now.
Maybe try a couple of things I tried and see if you find similar results.

 

[Old.Tony]

^ If the unit you tested with a multimeter was the Boost Control Solenoid, there's no surprise that it tested ok. The BCS oscillates at 100Hz, the internal circuit may test ok but be unable to move the valve inside.

 

[BarneyB]

.....I was brave enough to simply order a new one at $275 (genuine Nissan but not from Nissan) and have since fitted it and it is going very nicely now. Added bonus, it is using noticeably less fuel.....

I was thinking you ordered a new genuine turbo charger for $275 ?!!
Where??!!.....I'll buy two!!

 

[Olpha]

I was thinking you ordered a new genuine turbo charger for $275 ?!!
Where??!!.....I'll buy two!!

Haha sorry BarneyB I forgot to put in that it was the BCS that was the identified fault I bet that gave everyone a bit of a surprise when I said it that way.
Hi Old Tony when you explain that way I'm not surprised with the outcome. I did think it was a little bit strange that the workshop manuals gave a resistance value reading only.