Navara 2010 2.5 diesel fuel consumption

[jayk]

..ta mate!

 

[apcconstructions]

Poor Fuel Economy

Bad fuel consumption diesel Navara D40.

It appears to be only the automatics which have a DPF and fuel consumption issues.

Everyone I have talked to with a manual is getting around the
9.5-10.0L/100km while everyone with an auto appears to be getting around the 13-14.5L/100km

I have a 2006 auto d40 which gets consistently 10.5 from day one with no running in etc. I have just purchased a 2010 d40 diesel thinking that I should be getting the 10.5 - NO i am getting 14.5L, this is despite filling up at the same petrol station and same driving habits as my 2006 model. Country driving around 110km/hr and still getting 14.5L/100km

I have cored out a 50mm hole through the factory dpf and it appears to have increased fuel economy by about 1.5L to 13.0/100 without throwing error codes. Blocking EGR seemed to make no noticeable difference so I unblocked back to factory setting.

I think I might have stumbled onto something. There is a O2 sensor just behind the DPF which is used by the ECM to trim the rich/lean mixture while in crusing mode. The sensor is a Zirconia type which measures the exhaust gases and lets the ECM know whether the engine is running rich or lean. The ECM then shortens or lengthens the time the injector stays open to trim up the fuel ratio mixture. The O2 sensor(or air fuel ratio sensor) can only measure whether the engine is running rich or lean it cannot measure how rich or how lean the engine is running.

The O2 sensor works by giving of a voltage depending on how rich or lean the engine is. The perfect burn ratio will cause the sensor to give off .45 volts. Any voltage higher than this means the engine is running rich, any voltage lower than this means the engine is running lean.(do a search on wiki to go further into how the sensor works) The idea of the sensor is that the ECM gets a feedback from the sensor that is say .6v (rich)so the ECM reduces the injector time to lean out the engine, the ECM then gets a feedback from the sensor of say .3v(lean) so it then lengthens the injector time to rich en up the engine. This happens back and forth many times a second which hopefully causes an "average" to be near the perfect air fuel ratio.

I did a simple experiment where I piggybacked my multimeter onto the sensor wires(white and blue) and instead of getting readings above and below the perfect fuel ratio voltage of .45v the sensor was showing the voltage always above .45v (actually between .5 and .75v)

This could mean only one thing.
The ECM is not adjusting the fuel mixture according to the sensors feedback - as the engine is constantly running rich.
The only way this can happen is if the ECM is in open loop mode where it ignores the sensor and follows a predefined Fuel MAP which are always a rich mixture.

The ECM usually only goes into open loop mode when the engine is cold or you have dumped your foot and want to go fast so it is not interested in saving fuel.

The engine is not throwing any fault codes so in my case there is a big problem somewhere in the ECM programming.

It would be good if anyone else that is having fuel problems with the auto's to see if they can get the senor reading ( you have to be driving and the sensor plug must be plugged in) or use a scan gauge.

I am due for a service soon so I am going to get Nissan to connect their diagnostic device while the car is driving as this would most definitely. cause bad fuel consumption.

I will report back their findings.

Maybe the tech minded guys would have some feedback on this!!

 

[Old.Tony]

If the ECU has started using a bad fuel map, make it relearn the fuel map by resetting it.

I thought the 2010 autos didn't have a DPF? Several people have reported that the DPF is missing on their 2010 autos. Doesn't mean there's no sensor in the exhaust for the exact reason you describe - it's probably in the dump pipe.

Our DPFs have sensors but I believe they measure pressure before and after the filter matrix and not oxy levels, to determine when the filter requires a regen cycle.

Still, your idea sounds pretty spot on the money, and that's why we've been resetting our ECUs. There's a lengthy way, or an easy way to do it. I like the easy way - don't forget to empty the vehicle of any load (inside or behind) before taking it for the gentle "learning" drive.

 

[Leprechaun]

I can't see any reason why you should need to do a fuel relearn unless you have changed something significant.

Country driving at 110kph, 13-14 LPH doesn't sound excessive to me.

 

[Leprechaun]

I thought the 2010 autos didn't have a DPF? Several people have reported that the DPF is missing on their 2010 autos.

The ST & KC, 126kW engine will still have a DPF.

 

[Old.Tony]

I'm getting 11s and 12s with Veronica tipping the scales at 2.5tonnes. I tend to try and keep my actual speed below 100km/h so it's just sitting on the upper part of the torque curve climb. I also don't rev over 2500rpm unless I need to (even when towing).

Driving style does account for a lot, but seeing a difference in vehicles by the same driver, I'd be looking at the vehicle first.

 

[apcconstructions]

If the ECU has started using a bad fuel map, make it relearn the fuel map by resetting it.

I thought the 2010 autos didn't have a DPF? Several people have reported that the DPF is missing on their 2010 autos. Doesn't mean there's no sensor in the exhaust for the exact reason you describe - it's probably in the dump pipe.

Our DPFs have sensors but I believe they measure pressure before and after the filter matrix and not oxy levels, to determine when the filter requires a regen cycle.

Still, your idea sounds pretty spot on the money, and that's why we've been resetting our ECUs. There's a lengthy way, or an easy way to do it. I like the easy way - don't forget to empty the vehicle of any load (inside or behind) before taking it for the gentle "learning" drive.

My stx model sure has a DPF, it also has two temp sensors,one before and one after the dpf to measure the exhaust temp when it does a dpf burn. It also has two 8mm diam alum tubes ( go to a pressure sensor just next to the ABS module on the passenger side of the engine bay)- these two tubes one before and one after the dpf measure the pressure difference before and after so it knows when the dpf is blocking up and can then initiate the "dpf burn".There is also a third sensor behind the dpf(has 4 wires coming out) which is the O2 sensor. This is the sensor which is responsible for "trimming up" the fuel map.

From what I can gather from reading the nissan workshop manual there is a default fuel map which the ECM has that will run the engine slightly rich and the manufacturer knows won't cause any problems except high fuel consumption if any of the sensors fail. The ECM trims this fuel map up and down via the use of the o2 sensor. The problem occurs when the sensor gives out values outiside of its expected operating values( the ECM does have upper and lower voltages that it expects to see cycling from the sensor in order to trim up the fuel mixture - and the ECM does regularly check these parameters) If the sensor consistently gives out readings that are not expected by or within its "expected" parameter range the computer thinks the sensor is faulty or not ready and will go into open loop mode and run the engine on the default fuel map ie disregards the feedback from the o2 sensor - Thus resulting in higher fuel consumption.

I have reset my ECM a number of times and it doesn't appear to make a huge difference.

There may be a bug in the ECM programming as the workshop manual says that it will throw an error code if the sensor does not send out the correct voltages within its "expected range"In my case the sensor is definitely not providing the expected feedback that the computer wants to see ( from the test figures that the workshop repair manual states) and thus putting the ECM back into open loop mode.

This may be a common problem and if the ECM is not throwing a code then the dealer will not realize there is a problem.- Including Nissan

My d40 STX is a king cab and the fuel figures of 13-14L100km are freeway driving when the ute is empty 110km/hr. Besides as stated before my 2006 auto model gets 10.5 and so does the 2009 mazda bt50 diesel I have, one of my mates has a Isuzu diesel auto also getting around10L100km. Using 40% more fuel is not acceptable and there is definitely a problem. Nissan either knows about it and doesn't want to recall faulty or uncalibrated sensors(cost about $300 each and lets face there is no damage occurring just excessive fuel consumption) or there is a simple programming error in the ECM by not throwing an error code meaning that Nissan or the dealer think everything is fine.

Something is definitely not right and hopefully after my service next week I might be able to report back what comes of it.

 

[Old.Tony]

If your O2 sensor isn't returning the correct values, then maybe it has a fault and could be replaced. I would be arguing with the service guy that my car is supposed to be getting somewhere near the mileage stated and if you've determined that the results from that sensor are incorrect, proving that to the service manager ought to be enough to convince them to closely examine it. If they can get the same results, they'll log the fault with Nissan who will then authorise the replacement.

Without that authorisation (which then results in Nissan wearing the cost of the part, not the dealer) the dealer will fight you. They've done it in the past and there are several threads here testifying to that (I'd look in the Rants section if you were curious).

If it IS the O2 sensor, there are a number of people here who would be really quite interested in it - I think 08Kingcab and Justdrinkbeer both get fuel consumption above the ordinary and they've tried several different approaches. You're the first one that I've seen that has actually examined the return values of the sensors and figured how the thing works. My hat goes off to you for sharing that with us!

 

[Leprechaun]

My d40 STX is a king cab.

Well there's your problem! Add your name to the list of unsatisfied KC owners.

Only thing the dealer will do is a ECM reset, then tell you it's all within spec. It's their standard fuel economy query scripted reply

By the way your airfilter is no better than a pair of fish net stockings, if you open up the filter box you'll see a layer of dust on the wrong side of the filter box. Fortunately you can get a Unifilter now, I just fitted one 1K ago, First time in 50K dust hasn't being ingested, too late though my turbo impeller is F***D.

Also when your suicide doors drop (not if but when) You'll really appreciate the mistake you made buying the KC, when the dealer tells you there is no door adjustment and you'll just have to live with it.

 

[Arty_74]

Excellent reading apcconstructions, I like many would be very intersted to hear the results from your service.

I have the 08 TD auto and am constantly getting around the 13 to 14 l/100, I am dissapointed with these figures as this is my first diesel vehicle and changed from petrol to diesel for the fact that I would get much greater mileage!

This is the first post that I've read where someone has looked further into the problem as to WHY it is happening, how can a Nissan rep tell us that 12 or 13 l/100 and upwards is within the acceptable consumption range when the specs say 10!!

My previous V6 Prado did 11 l/100 (mainly hway)

 

[Leprechaun]

Why don't you remove the DPF and fit a delete pipe? $400, if it is the cause of your fuel economy woes then you'll make that money back in no time.

 

[Old.Tony]

08Kingcab, you raise a very interesting point.

What happens to the sensors with the delete pipe? If the issue is a ECM mapping failure, caused by an errant O2 sensor, does the delete pipe have any effect? I'd think not, but I don't know how the sensors are hooked up in the delete pipe (if at all).

Another good question is this: if the sensors are not hooked up in the delete pipe, where are they and how is the ECM operating on the basis of the (obviously) invalid return data from the sensors? Is the ECM simply staying in 'default' mode - which by what we've just been told is a slightly rich "safe" mixture?

 

[MintR33]

08Kingcab, you raise a very interesting point.

What happens to the sensors with the delete pipe? If the issue is a ECM mapping failure, caused by an errant O2 sensor, does the delete pipe have any effect? I'd think not, but I don't know how the sensors are hooked up in the delete pipe (if at all).

Another good question is this: if the sensors are not hooked up in the delete pipe, where are they and how is the ECM operating on the basis of the (obviously) invalid return data from the sensors? Is the ECM simply staying in 'default' mode - which by what we've just been told is a slightly rich "safe" mixture?

If its similar to a Cat delete pipe the sensors usually screw back in... $400 seems a bit steep though, might be worth talking to an exhaust shop to fab something up...

 

[Leprechaun]

Buy one, copy, then resell the original.

I do it all the time.

 

[Chip Tuning]

sounds like your sensor is faulty. U could run a pull up resister to make the voltage you need ... say .6 volts

 

[westy350]

apcconstructions,

Mate I feel your pain I have been trying to beat the high fuel consumption ever since I rolled out the dealership, I have got the DPF delete in at the moment didn’t really make that much difference, did a little but not as much as I expected, Now I’m with you I’m thinking its the oxygen sensor that is causing the ecu to use more fuel. How did you go with your service did the dealer give you any helpful info? all we really need to know is the signal the ecu needs to see to think that everything is ok do you know what it is or does anybody else out there? Then we could put a variable resister on it and tweak it until the ecu gets what it wants. Looking forward to hearing your results.

 

[Old.Tony]

A thought just occurred to me ...

The return value from the O2 sensor in the DPF is used to adjust the fuel mixture in the ECU.

This means with a variable resistor in a neat little box (including an "Activation" switch and corresponding red LED to indicate that the box is now connected) I could mount this in my car, replacing the O2 sensor return with the fake signal from the variable resistor ...

I could market this for $1200 a pop. With box, LED, wire and all, that's about $1,195 profit per car.

 

[Arty_74]

Just did a quick calc -
car 1 - 10LPHK - travelled 500km - used 50 litres of diesel @ $1.28/l = $64.00
car 2 - 13LPHK - travelled 500km - used 65 litres of diesel @ $1.28/l = $83.20 .... my car (

I'm approx $20.00 worse off each tank than the guys with manuals!!!! aaaargh
and using around 15 ****** litres more each tank

That seems like alot when you look at it this way

 

[westy350]

Could you put a ECU from a 2007 auto without DPF into a 2008-2010 auto with DPF if the DPF had been deleted? recon it would work?

 

[Krankin]

I'm gettin an avg 9.5l/100.