2 Month old 2.5 Navara blowing excessive smoke

Hi guys my 2010 ST blows so much smoke some times it's embarrassing, definitely don't look in your mirror at night when you pull away from the lights , clouds I say.

I was behind a not-too-old D22 with a 2.5L diesel yesterday and it pumped a bunch of black smoke, but the driver was using a fair bit of accelerator. I don't drive around behind myself enough to notice - and I suspect that if I drive around in small enough circles so that I can see my own exhaust, I'll eventually park the Navara in its own tub and disappear. I don't want that to happen!

I'd love to get my hands on one of these "excessive smokers" for an hour. Assuming that the vehicle is mechanically sound - no piston ring damage, no turbo bearing damage etc - then the smoke can only be caused by overfuelling.

The car knows how much air is coming in - there's a Mass Air Flow (MAF) sensor in the intake that tells it. If the air filter is blocked up it will know about it and may compensate with less fuel. That doesn't mean that it's perfect - the output from the MAF is not defined as a specific value, but a range of values, which leaves it open to errors.

It's the same thing for the fuel rail pressure sensor. Its output is within a certain range. If it's reading the pressure and returning a voltage at the lower end of the acceptable range, the ECU will see that as a slightly lower rail pressure and will increase the output of the fuel pump to raise the pressure.

That increased pressure directly becomes increased fuel delivered to the cylinder for the same injector open duration, and the engine runs richer than it needs to - and blows smoke.

Add to this a slightly higher-than-normal (but still within range) output of the MAF sensor and the overfuelling is more pronounced.

Thus a small variation in sensor readings can become enough. Fixing it isn't easy. Nissan would plug their unit in and read the sensor outputs to find them "in acceptable range" as per the manual.

This is where racing crews - or experienced mechanics with time on their hands - can make a difference. Don't accept a reading from the fuel rail pressure sensor that deviates too much on the low side. Same for the other sensors. If they're off-spec, replace them.

I suspect that a decent chip like Chip-It's chip actually would allow you to compensate for this by altering the fuel map manually. Robert, if it doesn't, then you might consider that as an idea for future chips, although I suspect that a vehicle that runs slightly richer could just use a lower setting to achieve the same as a "normal" vehicle.

Without spending any money on the vehicle you can still do things to help. Clean the air filter. Make sure your diesel comes from a good source - small outlets that don't turn over their diesel a lot might not have the best fuel in the tanks, truck stops are the best sources.

Then you can reset the ECU too - the thing learns all the time, and if it's overfuelling, it will continue to do that even while it's learning to reduce the amount of fuel. Start afresh by resetting it and then see how it goes.

i had mine at nissan on tuesday, they said everything was OK, still blows smoke but, they said they have had heaps come back and its normal for these vehicles, i believe thay have no idea. i have a egr blanking plate to install on the weekend, will see how that goes.
cheers
geoff

geoffd40 said:

i had mine at nissan on tuesday, they said everything was OK, still blows smoke but, they said they have had heaps come back and its normal for these vehicles, i believe thay have no idea. i have a egr blanking plate to install on the weekend, will see how that goes.
cheers
geoff

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Geoff, you're just up the road from here (sorta)!

Have you got some Permatex Ultra Blue handy? Use it on both sides. The side facing the exhaust to stop the exhaust gas from leaking out into the engine bay. The side facing the EGR valve to stop turbo boost pressure leaking out.

This is my first post so hope it helps! My 24 month old Navara began blowing excessive smoke a month ago. I changed the fuel and air filters with little change. I took it back to the dealership, they put it through numerous test and found the injectors needed to be replaced(luckily still under warranty). I now have a smoke free ute and had no drama from the dealership.

I had injectors replaced on my 09 d22 last year because of excessive smoke. Ran fine for a while, now 13k latter it's smoking up again. I am thinking of doing this egr mod, but hesitating while it is still under warranty.

done the egr mod over weekend, very simple, took about ten mins, cant even notice it is in there from the outside, seems to have cut the smoke back quite a bit, highly recomended, will do the computer reset tomorow, see how that goes.
cheers
geoff

if its not low on power, missing, running rough or hard to start first in the morning there is nothing wrong with it. same as some of the other guys said try blocking your egr off. just a simple case of not enough air. i have noticed all d40's do it. being a diesel mechanic i know that if the engine has not reached the desired boost pressure it will keep ramping up the fuel intill it reaches boost.

Old.Tony said:

And the commonly installed catch can is attached to the output of the PCV (Positive Crankcase Ventilation) to catch the engine oil.

Diesels (much more than petrols, although they do it as well) allow some of the combustion gases to slip past the piston rings. "Allow" isn't really the right word - the goal is to minimise it, but anyway, the force of combustion squeezes some of the gas down the side of the piston and into the crankcase area.

This pressurises the crankcase area. Hot oil will splash, some of it will turn to vapour and it will be forced out the pipe that allows the higher pressure to escape. In the D40 engine (and perhaps the D22 as well, I didn't go looking) there is an oil trap in the top of the engine, but still some oil escapes - this is fed into the air intake between the air filter and the turbocharger inlet (because you don't want to try and push boost into the crankcase!).

A catch can will trap that oil and allow you to rescue/re-use it later.

Does it affect emissions? Not really. The specification for the crankcase oil in our diesels is JASO-FD - that's the highest rating for low-ash oil generally available. This means that if you burn the oil, it produces very few particles - it burns very cleanly.

So your catch can won't assist in emission control, but it might catch a little of the oil that the engine can't. Is that worth doing? Many people think so, and I'll do it as well, eventually.

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great explanation, i had a bad case of this on an old turbo nissan (petrol) i had years ago, was 'breathing' pretty bad and coating my afm in oil and inside of my cooler pipes were coated in it, installed a catch can and it overflowed within weeks, ended up being a blocked pcv valve, took it out, sprayed it with carby cleaner and shook it till it moved freely, never had an issue again, i was so worried my rings were stuffed when the problem was fixed with a 2 dollar can of carby cleaner!

krunchi said:

Also being new does not garrunatee ur EGR valve is working right.
Mt d40 after 1000k developed weired EGR valve problems.
Blocking it off is the best solution, Nissan will never fix it if its EGR related.
Come to think of it , Do nissan fix anything on our cars?

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I'm with you, they do the bare minimum just charge like a wounded bull for servicing and on a warranty its like they are paying for it.