2012 M56 Exhaust soot

[The_Murph]

Hi,
I have a 2012 M56 with about 6000 miles. I noticed that the SS exhaust tips are always covered with black soot and my gas milage has been droping in normal interstate driving. Also if you punch the throttle from a stop or slow roll it looks like a city bus taking off with a big black cloud behind the car. Is this normal for all direct injected gasoline engines, or is something going wrong with the fuel system?

[qship96]

Not normal, sounds like it is running rich,which explains both the soot,black smoke, and reduced mpg. You are under warranty, take advantage of it.

[The_Murph]

Thanks qship96!

[SteveTheTech]

Greetings, The_Murph

First off Kudos on the second year M56. That car is really an absolute blast to drive.

Around these parts we tend to see things like this around this time of the year.

I have a few questions, things I could not get from your post or info.

Where are you?
What type of fuel are you running?
How long have you had the car?
Have you ever taken the car in to the dealer? There may be an engine control computer software update.

There are a few things that make the M56 different than other vehicles from Nissan or Infiniti.
The largest difference is the fact that the 56 has direct injection and highly variable valve timing intake and exhaust timing. The amount of air and fuel even at high load produces more solid carbon than the average smaller displacement engine, this is true in many forced induction engines and may not indicate an issue. Fuel grade and seasonal blending will vary the amount of soot or smoke you might see. Despite having quite a large engine it tries to get the best fuel economy possible, it does this by altering valve timing and exhaust overlap. What that may tend to do under normal conditions is not allow the by product of normal combustion to clear the exhaust system completely. Forcing several hundred if not thousands of grams per second of exhaust through pipe will literally blow the bats out of it under median to high load, especially if you were idling or under very light load.

[The_Murph]

Greetings StevetheTech,

To answer your questions:
1 I live in central Illinois
2. I'm running premium unleaded, most of the time with no ethanol
3. Had the car just over 4 months, and it has 6000 miles on it.
4. I haven't taken the car to the dealer yet as it is a 150 mile trip one way, so it's not too convienent. I also saw on Freshalloy, another owner had like problems and it was fixed by replacing the injectors and fuel rail. The diagnosis was a stuck injector. That could happen as the fuel system is dirtiest when the car is built and then you also have to 2 month boat ride from Japan that things can stop working properly just not being used. I know they had terrible engine and transmission calibrations on the 2011 model that was fixed with a software update. I picked up on that during a test drive of that model and refused to purchase a car that didn't run right. That software fix was incorporated in the 2012 model.

The car is not at idle or super light loads for any extended period of time. This black smoke problem can occur after a mostly highway trip of 25 miles at 60-65 mph and if your at a stop sign and take off with wot or 3/4 throttle, you can get a huge cloud of black smoke out the tail pipes that nearly completely obscures the car behind you if you look in the rear view mirror. Not unlike an old diesel city bus taking off from a stop. I expect a 1-2 mpg drop with winter fuel, but my ecconomy seems a lot lower than others who get 27+ mpg at 70-75 mph, and seems to be getting worse over time.

The other indications are the exhaust tips and lower bumper are black on the outside even after a 200 mile interstate run and the oil seems to contain excessive amounts of soot even after only 1000 miles. After only 1000 miles the oil is as black as night and what you might expect to see after 5000-7000 miles on an oil change. With 8 cyl and if one is running too rich it would be hard to notice that in a performance change, hence the other indicators become significant.

[SteveTheTech]

4. I haven't taken the car to the dealer yet as it is a 150 mile trip one way, so it's not too convienent. I also saw on Freshalloy, another owner had like problems and it was fixed by replacing the injectors and fuel rail. The diagnosis was a stuck injector. That could happen as the fuel system is dirtiest when the car is built and then you also have to 2 month boat ride from Japan that things can stop working properly just not being used. I know they had terrible engine and transmission calibrations on the 2011 model that was fixed with a software update. I picked up on that during a test drive of that model and refused to purchase a car that didn't run right. That software fix was incorporated in the 2012 model.

I don't know if I quite agree with your assessment here. There may be an issue with a sticking or improperly flowing injector but if the tailpipe emissions were to exceed 20% of the federal mandate the SES would come on. There is no maybe about it, if there were raw fuel being dumped into one of the cylinders the SES would begin to flash as that poses immediate risk to the catalyst. There have been only a limited hand full of incidents that I have heard of regarding the direct inject system mostly very isolated and I cannot think of one that did not have an SES complaint with it.

Nissan has been shipping cars all over the world for decades without an issue I do not quite agree with your comments about dirty fuel system components. They are filled with different quality fuel but haven taken fuel systems apart over the years I have rarely seen any dirty or debris make it into the lines when the proper fuel quality is used. Engine and transmission calibration and unset adaptives are two different things. I have been telling people since these cars came out to seriously look into driving a car will 2000+ miles on them as a first test drive. These cars are quite quirky (as I am sure you know) when they have low mileage. Their shift timing is odd at best, although quite efficient and they get down to business when needed. However having an ecm update really helped their first year jitters.

There are many things that could cause that. It will most likely be one of those things that you are not able to pinpoint until a code is set somewhere. Personally I would not worry too much about it there is far more than enough warranty left on your car to cover anything for the foreseeable future. The dealer will most likely not be able to do anything if they cannot locate the source of a problem.

You may not be able to notice a performance change if the engine were slightly off...but your car will know.

[Frog]

Are there any updates to this issue?

[The_Murph]

Frog,

I've brought this issue up to the dealer and no resolution other than Infiniti engineering says that is normal for this engine. My car now has about 34,000 miles and soots the exhaust tips and rear bumper like always. Especially on a long highway trip where it gets into lean burn mode.

[Panzer Leader]

I would bet it is the Direct Injection. Why? Because I had a 3.6 SFI G8 No soot at all. After that two 3.6 DI CTSs, tailpipes fouled constantly.... I would also suggest that you get a Catch Can installed.