D40 Fuel Economy

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Hi Guys, first post on here thanks for having me, I hope I am in the right section?
I have recently brought a Navara D40ST (4x4) 2.5 Diesel, Turbo, Auto Tranny, Dual Cab, 100k on the clock.
Neat all round car that has been looked after, it has an enclosed canopy, bullbar and has been slightly lifted. Have replaced the mud tyres with standard size tyres (original diameter).
Ok car was chewing 20 litres every 100clicks, they adjusted the rail pressure, reduced it to 18litres per 100 (diesel was evident on tailgate)
Following week (I complete a 1000kms at a time on country roads) they replaced the Air Flow switch and reduced consumption to 14.5 litres per 100clicks)
Now being told that's the best it can do, when clearly this and other forums illustrate they can do better and closer to manufacturer guidelines?
I have also read (gee I have read some stories on these cars!!) that the injectors could be RS?
The car is still under the yard warranty and they are still pretty responsive to my calls to fix it.
Is there anything further I can suggest they undertake to reduce the consumption further? I could live with 12litres, but 550kms to an 80litre tank is killing me with all the country driving I am doing? Thanks in advance, really appreciate any suggestions and I will continue to scan other posts.
cheers
i
 
Yes the injectors could be toast, but before even considering that, there are other things to look at. Knowing the year model of yours is important - at least it lets us know if you have a DPF. Look on your dash as you turn on the key - if there's a light like you see in the below photo in the bottom centre, you have (or had) a DPF fitted to the vehicle and that could be the cause.

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The DPF needs to "regenerate" and when doing so, uses some extra fuel. If it's doing it all the time, you could be using quite a bit of juice. If your DPF has been removed (look under the front passenger floor, the DPF is a larger tube that mounts inline in the exhaust and has several little pipes coming out of it. If yours is missing and you have the light, maybe your DPF sensors are shot - you should talk to auggie (a user on this forum) about some new sensors.

If you don't have the light, other things that can cause extra fuel consumption are:

1) Dragging brakes. Drive the car for 5 minutes and feel the hub/wheel nut temps. They should all be the same temp and not overly hot.

2) CAS misalignment. If the car starts well and idles smoothly the CAS is probably fine, but if it's a little hesitant the timing needs to be checked.

3) Faulty/failed turbocharger actuator. Some of the ST models had electronic actuators that needed to be replaced by Nissan. If it's vacuum-operated, it could be vac hoses (very common), vac solenoid (common), brake booster (uncommon, accompanied by poor braking performance), actuator diaphragm (uncommon), vac pump (very uncommon).

4) Faulty fuel rail pressure sensor. Possibly it's been interfered with by a performance chip, which often modify the return signal to fool the ECU into raising the fuel rail pressure.

Questions:

a) Is there any smoke evident, at various times, and what colour is it?

b) Does the car perform well? Dragging off Hiluxes at the lights can be done in Park with the engine off, handbrake on and a chain tying you to a nearby pole so that's no real test, try dragging off a performance vehicle like a Hyundai Getz. Can you do it?

c) Does your car have a performance chip? Try disabling it. There may be a control for it in the cabin (DP Chip, Steinbauer, ChipIt, Unichip, No Limits - there are many to choose from, some infinitely better than others).
 
Hi Tony

Mate thanks for the reply it's much appreciated!
Sorry my car year is 2010, late build and from the service records its been utilized all it's life up north, assuming long trips. It also had a trailer brake and the previous owner towed a caravan with the car as I have seen photos.

On the light you have added above, I have not seen that one come on at all. The ECU? or the exhaust light top middle yellow was on when I first purchased the vehicle and the mechanics fixed that (needed welding or repair) and the diesel specialists have "reset" all that is required to be reset with that particular warning light after I advised them it had been on (I have been also advised from a number of plant mechanics the diesel guys currently looking at the car are onto it and one of the best in the business in Perth, they appear to me to be competent).

I unfortunately can't check if DPF you mentioned above has been removed as the car is still in the shop, but I will ring and ask them, though I haven't noticed any thing missing when I last had my head under there.

Point Number 1 - had a mechanic go over the car and brakes were checked so pretty confident this is not the issue.
Point Number 2 - I will ask them to check this, though the car does idle ok and since the air flow meter was replaced runs a lot better.
Point Number 3 - I will ask them to check this
Point Number 4 - I asked them if it had a chip and they said no, I will mention that as well.
Point Number 4a - haven't noticed smoke or indeed excessive smoke and to be fair haven't taken notice of color. There was a bit of excessive soot in the exhaust, but this has reduced since they made the rail pressure adjustments.
Point Number 4b - Mate the they are not a Porsche if that's what you mean, but overall since they have made the last lot of improvements the car has performed ok and accelerated fine when overtaking. I have been driving the car "consistently" as i can to provide the best indication of fuel use, though not been scared to slip the slipper in to overtake on country roads. Seems to go ok when doing this.
Point Number 4c - No chip in the car so i have been told!

Many thanks
i
 
Late 2010 probably has no DPF, and the absence of that light means the device was not fitted to your car (or someone's clever with black paint, I'll bet on the former first).

The yellow engine light is the "Check Engine Light" (CEL) also referred to as the "Malfunction Indicator Light" (MIL). If it lights up, the ECU thinks there's a problem and it will have stored a code for it. Any decent mechanic's shop will have a widget that can read those codes. For $10 you can have one too - get an ELM327-compliant bluetooth OBD2 adapter and use an Android phone with the Torque app. That code gives you at least a starting point for problems with the car (although it's sometimes misleading, at least you have a beginning).

If performance is ok then it's probably going to come down to tuning/injectors, but let's see how it goes once you get it back.
 
Hey Tony

Mate thanks again, it's bl00dy handy having other opinions when talking to these service guys, sometimes although you know your right you find yourself self doubting!
The good news is they rang me today and said that the injectors were indeed over fueling and they are putting new ones in. Some of the other members mentioned similar problems on the forum so it helped me a bit a bit firmer in my request for them to be looked at!
thanks for the advice
regards
i
 
Hey Tony

Mate thanks again, it's bl00dy handy having other opinions when talking to these service guys, sometimes although you know your right you find yourself self doubting!
The good news is they rang me today and said that the injectors were indeed over fueling and they are putting new ones in. Some of the other members mentioned similar problems on the forum so it helped me a bit a bit firmer in my request for them to be looked at!
thanks for the advice
regards
i
Good to hear you found your problem how much did the new injectors cost and wich ones did you use
 
Hi Subz
I am not sure which injectors where used (they are still undertaking the work) but they were not supplied from a Nissan dealership, it was a specialist Diesel Injector supplier. The guy said previously they were 2.7k for new injectors, not including install costs.

Yes fingers crossed that this has indeed fixed the problem.
I have learnt heaps from this site and your members, so keep up the good work, although I am hoping for further hassle free Navara motoring in the future, I am sure I will need to come back again! Thanks again for all your advice
regards
i
 
Hi Guys

I had my car back last week, they replaced the injectors and the booster valve? Booster something (around 400 bucks worth apparently).

The car is now running much better and not revving as much and since these new injectors have been fitted (plus the booster valve) and I completed 1000kms of country driving but could only still manage 12.65 litres per 100kms. Been told this as good as it gets, its an Auto and they chew juice!

It would be better if I could get closer to 10litres per 100, but it's so much better than the 20 I started off with and I am pretty sure if they see me coming back through the door there might be some spanners coming in my direction!

I will keep my eye on further suggestions and see if I can get it any better? The diesel guys did say they hadn't witnessed so many components going out within 100kms so maybe I just brought a big yellow lemon? :)

cheers again
regards
i
 
12.65LPHK is much better and it's actually close to "normal".

We did 1118km in one direction and use 120.9L (10.6LPHK) with 4 adults plus clothes for 2 weeks and some food and a few tools and other bits and pieces. The car would have easily been over 2500Kg but not sure how close to its 2980Kg limit it was.

We then came back, doing 961.7Km using 118.9L (12.1LPHK). Same people, same load.

The difference? On the first trip, I didn't let the car go over 90km/h. On the return trip I went at the speed limit (up to 110km/h).

Try a decent trip at a slower speed?
 
speaking briefly about [ fule injectors ] my ex pajero was diognosed with worn out injectors and the replacement cost was a joke [ over 2k ] i took the car to a deisel mechanic who had a good injector cleaner unit, he cleaned all 4 injectors and the engine ran better than ever for over 70,000 klms until sold.
what he did say that many mechanics will just replace the injectors with expensive new ones just to make the quick and easy buck, any fuel injector is worthy of atleast one cleaning in its life. forget the injector cleaners on the market he said you must have these cleaned with the machine. also i have seen new navara injectors selling for around the 7 to 800 dollar mark on ebay. bugger that $2700.
 
Flabergasted

I recently filled up after around town driving - 68 litres = 470km. 2010 D40 Diesel. Is something wrong? Never been much better?? Heading off on a trip soon towing a van. Will need jerry cans to get between places??
 
14.46LPHK is not all that good but there might be two things influencing it. First, if it's a King Cab it's actually not to bad - there should be a software update (that we have never found the internal reference for) that fixes it. Otherwise, if it's driven heavily - it could do it easily. It's 2T+ of genuine brick!

You could try a Liqui Moly injector clean.
 
Hey all. Been a long while. Just looking at this thread and I may have the most efficient car here. Haven't checked every post but here are my stats. 2009 ST-X 2.5 manual. Owned since new. 112500k. Original clutch. Shockers about to be replaced as its handling like a plank. My truck does a 37 km school run twice a day and mostly city driving around Bris. I get the warning light at 720kms. I usually fill up at 750 to 780kms. It takes 71 to 72 litres everytime. I get 9.5 to 9.7 litres phk. I usually dont flog it but it doesn't get nursed.
We are driving to Melbourne this christmas so i'll post up the highway mileage if i remember.
 
475 and the fuel light comes on.

Thanks Old Tony. We don't drive it hard so maybe something else. How can i get the software update? Is it a Nissan thing or is it available elsewhere? Ta
 
Last edited:
Auto Spanish D40

How lucky you guys are, 2007 d40 spanish 16l/100ks around town, about 400ks for 64ltrs. Os

the Spanish built D40's with the particulate filters are the worst for fuel economy, mines an 07 also, i get around the 14-15L/100km in my nav and i just know that thats what i should expect to see. its all to do with the regeneration process the car goes through every 250-300km
 
Mine's currently averaging 12.4-12.7LPHK. I've been able to get in the low-to-mid 10s on a pure highway cycle (driven lightly, but at about 2700Kg). I was doing worse, but I've had dirty injectors (Liqui Moly fixed it) which was easy to spot - the engine "hunted" or "surged" regularly when cold/cool. Also had a leaking gasket between turbocharger and exhaust manifold.
 
Im certainly a happy camper, 2013 Thai model and I've never gone over 10L/100km, usually sit in the high 9's, but do live rural, so quite a bit of 100k driving. Did a 700km hunting trip a while ago, constant 100k driving for a whole tank, fuel consumption in the 8.5L/100km range.
 
I think the big factor here is the tyer size when i had stock tyers i was getting 9.2/100L getting 720 to the tank then i up it to 32's and it went up to 10/100L dropped to about 680 to a tank now with 33's 10.8/ 100L and maxing out on 600 lol so big difference then stock
 

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