D40 V6 Petrol - Fuel consumption???

[Wetkit]

Hi Guys,

I'm new here and from the enemy country, RSA.
No sport discussions please, my rugby team is doing bad enough as it is

Anyway, I have had my D40 gas guzzler now for nearly 3 years.
It is a 2007 model, 4L V6, 4x4 and Auto.
Yes, it sucks juice not nothing else!!!
But I would not swap it for anything, except perhaps a 550

I used to get 18L/100km consistantly, town driving, highway or towing.
Only doing heavy sand driving in 4x4 used to change consumption to around 24L/100km (Land Cruiser and Patrol country).

Now, after my last 4x4 outing, the consumption is stuck on 24l/100km.
I can smell the unburnt fuel from miles away

I had it at 2 diffrent Nissen agents here. Both confirmed it is running way too rich, but none can find the cause for it.
There is no fault indicators showing up on the instrument panel, or checking via Consult computer.
Readings from A/F and oxy sensors confirm over fuelling but ECU not adjusting injector timing?
Run it on load, and it starts to lean out again.

I know you mostly Diesel guys here, but perhaps somebody could have some idea's?

Thanks

 

[Aussie Frontier]

Your consuption is way way too high. I would suggest maybe you have a slight fuel leak.have you done an ECU reset to get it to relearn its fuel curves?
I have the V6 petrol as well with a 6 speed and Im wondering why its doing 13l/100 .
I find the best fuel consumption is around the 1700rpm in cruise

 

[75 GRC]

Welcome to the V6 petrol family...
They love their juice!!!
What more can I say.
Cheers Geoff

YEP!GOT A V6 'BUT I LIKE TO CUSTOMISE.

 

[Wetkit]

Well, the Auto is way heavier on juice than the Manual, as well as the 4x4 vs the 4x2.

Anayway, yes, the ECU was reset and re-learing done.

 

[kernels]

Poor petrol fuel economy usually points to

* Dirty MAF sensor
* Bad Oxy sensor (sensors)
* Low air pressure in tyres
* Fuel system running 'open loop' instead of 'closed loop' - probably not this if consult is not complaining
* Vacuum leaks from inlet manifold / pipes
* Binding brakes / wheels / gearbox
* Check earth connections everywhere

 

[Aussie Frontier]

Yeah id be checking MAF and O2 sensors then as something is telling the ECU to go full rich
If however the strong fuel smell isnt from the exhaust im betting u have a fuel leak

 

[Wetkit]

Thanks guys.
Have redone all the earth connections.
MAF was cleaned.
Going to try and clean the A/F and Oxy sensors the same way as the MAF sensor. Hope it works...

How would one go about checking the vacuum lines???

 

[user 10312]

How is it running, does it seem down on power?

 

[Wetkit]

No loss in power.
Idling a little bit rough, but not so that it would raise alarm bells.

A friend now suggested perhaps 1 or 2 injectors that could be stuck open, or leaking.
From there that the ECU can not compensate for the over fuel at idle and low loads.
Sounds plausable to me?

Now, how to check those injectors without breaking something....

 

[Robboneo]

Has anyone checked you fuel pressure ??

 

[bods]

Injector cleaner... I'd suspect o2 sensors straight away, how many in on it?

 

[bods]

Has anyone checked you fuel pressure ??

That's a good point too, if the pressure regulator on the rail I'd blocked it could cause excess pressure which the computer can't compensate for..... More pressure = more fuel at each injection stroke......

 

[user 10312]

That does sound plausible as injectors holding open is a mechanical fault that will not show up as a code.

Why I asked that, if it was ridiculously lean it can still smell like unburnt fuel and believe it not you can still use more fuel but you will notice a real lack in power. Anyway rules out chasing anything down that road.

If a sensor goes out of range it should show up as a code but not always. This is a tricky one.

If you have the ability to start checking ranges of sensors I'd be looking at the ones that will have major changes on fueling. MAF, Boost, Throttle position, Engine speed/Crankshaft position. Sensors like Air Temp, O2, and to some degree. Coolant Temp have more minor effects on fueling.


I wouldn't worry to much about the O2 sensor sure it will affect fuel consumption if not going into closed loop but this would probably make a minor difference in fuel consuption not a major one as in your case.

Sorry I can't help more.

 

[kernels]

If an injector is stuck open you should be able to pull the electrical plug on it without it making any difference to the engine running. Pull the electrical connections one at a time and confirm that the engine stumbles with each removed injector.

Pulling the electrical plug makes that particular injector not open when it's supposed to, I'm 99% sure they close automatically.

 

[seventies47]

Did the dealer give you any idea on what data they were getting? MAF readings? O2 sensor outputs? A/F ratios? Injector pulse widths? Coolant temp reading? this data would be very helpful with diagnosing a mixture issue. for example, a extreme low coolant temp reading will massively increase fuel injection quantity, also showing as a longer injector pulse width. A 02 sensor stuck at lean will cause over-richening. but will only affect one bank (in most cases). A high MAF output will also increase fuelling. Ask them for as much info as possible if theyre unable to find the cause!!

 

[kernels]

Bugger, left a big one off my list, a stuck open thermostat will cause the engine to always run cool massively increasing fuel consumption.

 

[Wetkit]

Ok, at least some good news for now....
All injectors was removed and sent for testing. Of the 6, 2 of them was definitely not closing as fast as they should be and causing the over fuelling.
Now to see if rebuilding them will fix them, otherwise would have to wait for new ones.

 

[Wetkit]

Ok, just some more feedback.

2 of the injectors was found to be over fuelling. All of them was rebuilt and installed.
I was completely blown away by the diffrence it made!!
It feels like I have way more power and the engine responce is instant.

Unfortunately it is still overfuelling on one bank, so today they going to swap the two A/F sensors to see if the problem moves. If the problem does move with the A/F sensor, we will replace that. If not, I guess it would be time for a new ECU

 

[Wetkit]

Ok, so the A/F sensors was swapped left & right and the problem moved with the sensor.
The one oxy sensor did not look too happy either, so the decision was made to replace both, ouch!
Job was completed Friday late, so I have not had too much time to do a full tank, but from what I can see, it looks way better.
now back to around 200km on 1/2 tank.

Thanks to all that gave advice!

 

[Aussie Frontier]

Still seems a little high.
I usually get just on 200 from the first 1/4 of the guage
maybe 50 on the next 1/4 on a bad day maybe 100 on a good
On average running 95 RON I get an average of 13l/100 in the colder months so about 450 to 480 on 60ltrs of fuel