How to fix 2003 Landrover Discovery II V8 (4 litre) used excessive amounts of fuel

2003 Landrover Discovery II V8 (4 litre) used excessive amounts of fuel, but no leaking fuel anywhere and the fuel gauge is reading accurately …what to do next is to read trouble code with a LR specific diagnostic scanner like Foxwell NT510 and know what’s going on.

Car model and year: 2003 Landrover Discovery II V8 (4 litre)

 

Symptom:

Using excessive amounts of fuel

It’s not leaking fuel anywhere and the fuel gauge is reading accurately … it is not driving any different, no noticeable fuel smelling exhaust or anything else obvious.

 

What to do next and possible reason:

Definitely check for trouble codes with a LR specific diagnostic tester.

Drive your Disco without the MAF wire connector connected. If the problem stays the same it usually means a bad MAF sensor.

 

Update:

ok … just came from the garage … everything checks out and no codes … trim is good …oxy sensors good ….tps good … coolant sensor – good… sprayed the start ya ba&%$d around – no vac leaks detected …. MAF is clean ……. air filter is clean – non oil type …… no fuel smell from the exhaust .. no fuel leaks ….running 98 octane fuel as always …..

mechanic reckons to change the MAF( would have done at least 100k + km) anyway to see what happens … and also the evap purg valve as these can cause problems …?

on my 3rd or 4th tank of fuel from different garages .. no difference.

 

What to do next?

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.

 

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 computer’s 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.

 

Finally solved!

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 …

 

www.foxwelltool.com