Another black smoke thread…

[user 50884]

Hi guys perhaps someone have had the same issue as I’m having..

Black smoke on acceleration and a strong smell of unburnt fuel from the tail pipe.

If the cars been idling for a long time or after engine braking, you hit full throttle, the Ute sort of dies for a second then jumps back in again with a big cloud of black smoke.

So far I have replaced scv, boost solenoid, injectors and turbo.

There seems to be two different boost solenoids. One that’s constant and one that’s pulsing. My new one is a pulsing one, when I put it in I noticed that the pulsing is kind of slow. (The ones I’ve seen before is pulsing really fast) it’s almost like the vaccum is not strong enough but if you put your finger on the hose it’s quite strong.

It could also be the solenoid not getting correct signal to open and close?

 

[Old.Tony]

The solenoids operate at 100Hz in response to a signal sent at that frequency by the ECU.

There could be something else causing the lag & overfuelling. Have you cleaned the intercooler? I've done mine several times: using one hand, I block one side of the intercooler and pour petrol (gasoline) into the other side. I then block that other side as I invert the intercooler and release the upper hand as the pressure starts to build. Invert a few times then empty and look at the stuff that comes out. Repeat the whole exercise until what comes out has a hint of the colour of the fuel that went in.

Check the EGR tube for holes. Look for sooty black emissions from anywhere around it. If yours is older than 2012, you probably don't have an EGR flow meter and can safely block the EGR (do it on the intake manifold end where the gold EGR tube meets the EGR valve). EGR valves have been known to fail.

How good are the brakes? Have they been better in the past? You may have a vac leak inside the brake booster. Use a vac test tool to see if it holds vacuum.

 

[user 50884]

The solenoids operate at 100Hz in response to a signal sent at that frequency by the ECU.

There could be something else causing the lag & overfuelling. Have you cleaned the intercooler? I've done mine several times: using one hand, I block one side of the intercooler and pour petrol (gasoline) into the other side. I then block that other side as I invert the intercooler and release the upper hand as the pressure starts to build. Invert a few times then empty and look at the stuff that comes out. Repeat the whole exercise until what comes out has a hint of the colour of the fuel that went in.

Check the EGR tube for holes. Look for sooty black emissions from anywhere around it. If yours is older than 2012, you probably don't have an EGR flow meter and can safely block the EGR (do it on the intake manifold end where the gold EGR tube meets the EGR valve). EGR valves have been known to fail.

How good are the brakes? Have they been better in the past? You may have a vac leak inside the brake booster. Use a vac test tool to see if it holds vacuum.

The solenoids operate at 100Hz in response to a signal sent at that frequency by the ECU.

There could be something else causing the lag & overfuelling. Have you cleaned the intercooler? I've done mine several times: using one hand, I block one side of the intercooler and pour petrol (gasoline) into the other side. I then block that other side as I invert the intercooler and release the upper hand as the pressure starts to build. Invert a few times then empty and look at the stuff that comes out. Repeat the whole exercise until what comes out has a hint of the colour of the fuel that went in.

Check the EGR tube for holes. Look for sooty black emissions from anywhere around it. If yours is older than 2012, you probably don't have an EGR flow meter and can safely block the EGR (do it on the intake manifold end where the gold EGR tube meets the EGR valve). EGR valves have been known to fail.

How good are the brakes? Have they been better in the past? You may have a vac leak inside the brake booster. Use a vac test tool to see if it holds vacuum.

Thanks for the advice.

I’ll definitely try cleaning the intercooler

Forgot to mention the egr is already blocked off both at the exhaust manifold and at the intake

Brakes are very bad you have to push the pedal quite far down for it to brake. Not sure if it’s a lack of boost or just worn pads.

Do you know what pressure the vaccum should be?

 

[Old.Tony]

Do you know what pressure the vaccum should be?

Generated vacuum at idle should be between -94 to -96kPa (-940 to -960mbar, -705 to -721 mmHg, or -27.76 to -28.38 inHg) (from p186 of EM.pdf in the manuel* for 2006-2010 models).

The brake booster itself should be capable of holding vacuum. If it's not, the booster has a fault and that explains the poor braking performance.

* In English it's typed "manual" but this is for the Spanish version of the Navara.

 

[user 50884]

So I tested the above, no faults found unfortunately.

On other threads people are suggesting that the fuel pressure sensor can be the cause.

I struggle to see that too little fuel from some kind of blockage or air in the system could cause black smoke? Wouldn’t the Ute drive lean if that was the case?

 

[Old.Tony]

Absolutely right - black smoke indicates overfuelling, BUT ... that's a very relative term.

It's basically a specific amount of fuel for a certain amount of air. This means black smoke could be caused either by too much fuel or not enough air.

Too much fuel:
* Fuel rail pressure sensor not reading correctly. Often an issue with those that use chips, because the chips rely on modifying this signal in order to do their work. This is quite rare although performance chip issues have been seen)
* Dirty injectors (usually dribbling). Liqui Moly Diesel Purge is the most effective.

Not enough air:
* Turbo underboosting. Sometimes it's the turbo, not often failing but losing control (BCS failure or bad vac hoses). Other times it's a boost leak. Leaks are easy to find, look for black oily emissions on the air path between the turbo and the intake manifold.
* EGR valve fault. Adding EGR displaces air having the same result as reducing the amount of air. Blocking the EGR has been done by many.
* MAFS dirty. It's cleanable but only use electrical contact cleaner spray, never a solid object. Remove it from the air intake near the filter, clean, replace. It's $400 from Nissan if it breaks. I've cleaned mine and as long as you don't stick anything in the hole it's usually good.

I know you've dealt with some of these (like the EGR block) but I thought I'd put them all in one place.

 

[user 50884]

Thanks for that!

In regards to the EGR, is it still possible that a faulty egr valve can cause dramas although it’s blocked?

I’m guessing the egr valve signal still can confuse the Ute to add more fuel then necessary?

 

[Old.Tony]

Not really. The EGR valve is not actually connected to the fuel system at all, only the exhaust. The only link to fuel is through the ECU: when the throttle is at idle or at full, the EGR valve will NOT open, but will at other times. There's no feedback from the EGR to the injection system.

 

[user 50884]

Is it possible for the rail pressure sensor to be faulty although it looks alright on the car scanner? And no error codes?

 

[Old.Tony]

Absolutely. It only has to be a small amount out, but if that's the problem you might also be seeing it idle higher than expected (around 750rpm).

 

[user 50884]

How about the pressure relief valve? Wouldn’t really cause black smoke?
Same goes for leaks in the fuel system or blockage?

 

[Old.Tony]

If the pressure relief valve was faulty you'd notice the higher pressure and the ECU may compensate for it. Blockages or leaks tend to either allow air in (the fuel system is generally under vacuum, the pump sucks fuel from the tank).

 

[Supermike]

Had a similar issue on my YD25, turned out to be injectors were passing. So not fully closing/shutting off when they were meant to. When the truck was idling or engine braking the injectors would constantly fire too much fuel and it wasn't getting burned. Under load or throttle it wouldn't be an issue. I got lucky, they got replaced under warranty as it was an approved used Nissan.

 

[user 50884]

I’ve replaced all injectors already.
The smoke is still there but manageable now. Took me 4 different boost solenoids until I got there. Although the solenoids are new you can get all sorts of values if you hook up a gauge on it. Very confusing.
I feel like it smells diesel but as long it doesn’t smoke I’m happy..

 

[Supermike]

Yea you need to be careful with the BCS, a lot of genuine fakes out there

 

[user 50884]

Still not quite happy with my nav...

As soon as I start it I can smell it is overfueling even on idle..

Boost is 20psi, new fuel& air filter, oil change, new fuel pressure sensor, injectors and turbo. Cleaned out the intercooler and havent found any boost leaks.

Im worried that the pision rings or something along those line since the engine overheated a while ago and now has a new head gasket and cylinder head.

Just cant see what would cause it to run rich on idle..

 

[user 50884]

Some live data on idle:

Calculated engine load value 23.14%
Engine coolant temp: 76
Intake manifold absolute pressure: 99kPa
Engine RPM: 749
Intake temp: 44
MAF air flow rate: 12.79g/sec
Fuel rail pressure: 30390 kPa
Calculated boost -0.01bar
Calculated instant fuel rate 4.38 l/h
Instant engine power (based on fuel consumption) 18.75hp
Power from MAF: 17.15 hp

 

[Old.Tony]

That's odd. The rail pressure is great, but the fuel rate is over double what I'd expect at idle (around 1.7 l/h).

After all the work was done, do you know if the ECU's fuel map was reset?

 

[user 50884]

I’ve done the accelerator pedal reset multiple times and replaced the scv as well.

Is there another way to do a fuel map reset?

 

[Old.Tony]

That should have worked then, but here's my full procedure for doing the reset:

* Write down tripmeter value and have radio PIN handy
* Turn car OFF. Send any other person away for a couple of minutes
* Unlatch bonnet, get out of car and close door.
* Open bonnet, remove battery NEGATIVE lead
* Open car door, press brake pedal
* Reconnect battery negative (do it up properly), close bonnet
* Take car for a GENTLE drive for minimum 10 minutes
* Switch engine OFF

The disconnection from the battery forces the ECU to reset once power is drained (pressing the brake pedal). Normally they'll tell you to "wait a couple of hours" but you achieve the same with brake pedal in seconds.

The gentle drive gives the car the fuel map you're after.

Turning the engine off tells the ECU to save that fuel map.

That's how it's supposed to work, anyway. I've had an odd person here and there tell me it didn't work for them but the usual response is that it's worked, happpy days. Try it, see how you go.

When the injectors were installed, were they registered correctly with the ECU?