The OP is in Australia. They use a different method for determining octane ratings.

 

Good test for the MAF is to idle the truck and then unplug the MAF. Should run considerably poorer.

Also if you can, monitor your 02 sensor voltages while idling and driving. The two upstream sensors( bank 1 sensor 1 and bank 2 sensor 1) should be alternating between a high and low voltage. say .8 V to .2V just as an example. if they are at .45 they are not reading anything, this is normal at startup but should go away after the truck is warmed up. If it is stuck at .45 or the voltage is at whatever static reading and not fluctuating between say a value over .5v and below .5v then this is most likely your problem. O2 sensors are good for a change after about 100k miles anyway.
Go with BOSCH sensors and change all 4 at the same time, or at least in pairs( both banks sensor 1 or sensor 2) if that makes sense
I know you said your 02 sensors are good but I fought this for the better part of a year so thought I'd share...

Not sure how you aren't getting a fuel smell in the exhaust though.. makes me wonder if maybe you've got a plug somewhere and aren't filling your tank all the way. Not sure the likely hood of such but regardless, some more information-- it is a 25 gallon tank and when I am at a quarter tank I can usually fill around 18 gallons and when I get the low fuel light I can usually fill about 22 gallons.

Edit: also just trying to think of anything else, I've heard of stuck open injectors leading to gassy smelling oil, misfires, obviously more fuel consumption but you have no symptoms of anything other then poor gas mileage so, just throwing everything out there

 

OK ...... does not idle any different with the MAF unplugged .... ordered the new MAF sensor yesterday ... ebay is telling me 3-5 days delivery ...will report back on the MAF is changed.

took the standard 80 odd litres when i filled it last time ...... fuel light had just come on

 

how is it idling to begin with? Is it rough and a little bit of a shake? Does it smooth out with a little bit of throttle ? Or is it perfectly smooth to begin with?

and for the coolant temp sensor, what kind of temperatures are you running? Do you have the black 180 thermostat in already? You should be able to monitor the temperatures with the code reader. I think people average around 190 degrees with the black thermostat but you should see it build temperature from a cold start to tell that it is working

 

I am having a similar fuel consumption issue. New MAF, new injectors, one new upstream O2. Others are working normally.

I am suspect of my Cats. I've ordered new Magnaflow high flow Cats, and replace the other upstream O2 to see if that fixes my issue. My fuel mileage is not quite as poor, but I have a hard time getting better mileage than 11 mpg's, even with mostly highway driving. Following this thread closely.

 

Idle is smooth at 750 rpm to begin with and .... temps are fine ... cooling system is in good shape but not running the black thermostat ...yet.

 

I am getting a whopping 9 mpg. I have new Bosch MAF, new throttle body gasket, new injectors and upper manifold gasket, new cats, air filter and new walker O2s. No codes. 4 mile round trip drive in the city. Long Term Fuel Trims are around +/- 0.8%
I run 93 octane. I have SAI. New lifters, cam, water pump, head gaskets 10xxx miles ago.
What gives!?!?!?

2004 D2 SE7 148,xxx
4.6L

 

I use a Foxwell NT510 I believe programmed to interface with Land Rovers. I am also able to reset adaptations which is pretty much resetting the computers memory of what it has learned about how your engine runs ( fuel trim etc.). If you have replaced anything sensors like 02 sensors or MAF, I think it would be a good idea to reset them if you have the ability to do so. The foxwell unit is only like $100 USD and lets you do a good amount on land rovers and others. You may be able to replicate this by unplugging the battery and letting it sit for x amount of time but I can not verify that.

I would start here if you can

After replacing all these parts only thing for you to do is look at raw data and try and determine what part is either faulty or picking up an abnormal reading and post your findings here. data such as MAF reading, 02 voltages, etc. Whatever OBD tool you have usually has a function that lets you record the data.

Did you do a smoke test on your vacuum lines to ensure there are no leaks?

 

After all that, plus the miles your truck has on it, I would consider having the injectors cleaned. They may be partially stuck open and "dribbling"

 

problem appears to be solved ... after the visit to the mechanic the other day ....!

the code reader did show a fault with the MAF sensor .... this was initially put down to it being disconnected while running to see what the change in idle condition would be ,,, in this case there was no change.

fault code was cleared ,,,, maf sensor was removed for a visual inspection ... looked clean but was given a spray anyway with MAF sensor cleaner and replaced.

car was not running any different at this stage .... ie running fine ..... ran the tank down as normal and refilled it a few days later .... now my truck is not running any different but fuel economy has returned to normal ...... !

i have ordered the new MAF as mentioned ... not arrived yet ... will monitor and report back after another tank or so on fuel consumption.

??????

all good

Darren