Causes of excessive fuel consumption???

[cliff]

Hey guys and gals,

This is more a fishing expedition than anything else!! I'm trying to work out what would have caused a dramatic inrease in fuel consumption?? The only change I've made is changed the diff gears from 3.9s to 4.1s, installed an air locker in the front and shimmed the LSD. The old girl is a TB42e with just under 350k the head was done at 280k, however it has gotten hot once since then whilst towing.

Now I appreciate there is a search function, but 9 times out of 10 it doesn't get the results you're after anyway, so any help would be great.

Cheers,
Rich

[boots]

Dare say if its gotten hot and 350 ks on it , the injectors are in need of some love and attention .

[97_gq_lwb]

Quite common yet overlooked causes for excessive fuel on efi cars are.
Engine not reaching the correct operating temp or fluctuating from cooler or incorrect thermostats.
02 sensor needs replacing usually 70 thousand k's max then bin it.
Bad cats honeycomb melted over.
Afm needs cleaning.
Engine fault codes.

[MQ MAD]

Goin from 3.9s to 4.11s will effect economy
What sort of economy are you currently getting ???
Running hot when towing , well depending IF the radiator was properly flushed (or rodded out) when the head was replaced then it could possibly need it again
IF the rad wasnt cleaned properly its probably a tad blocked
Bit more info needed

[Silver]

Plus the usual stuff like check tyre pressures.

Thanks for the detailed posts above, by the way!

[billyj]

thermostat stuck open, faulty afm, faulty o2 sensor, dirty injectors, blocked airfilter, blacked exhaust

[cliff]

Thanks for the replies guys.

The following has been checked and not an issue.

Exhaust system, replaced this time last year. Including a highflow S/S cat.
Genuine thermostat and rad cap.
New ally 3 core radiator.
Air filter is K&N and was just serviced.
Nil fault codes.

Item that will be done thanks to your advice above.

Injectors to be recoed, or replaced.
O2 sensor replaced,
MAF checked.

If all this fails, I may just throw in a 304 and be done with it. lol

[97_gq_lwb]

Another thing could be the ecu recieving the wrong speedo signal vs tps .
Did you change the speedo drive gear to suit the diff ratio.

Would hate to see you throw a 304 in it the best place for a 304 to be thrown is in the scrapheap.

[billyj]

if your running a k&n filter i wouldnt be suprised if the maf is dirty, takes about all of 10mins to give it a clean with maf cleaner

[97_gq_lwb]

Personally i would ditch the k&n filter on a 4wd.
They block up quick enough on the street i would hate to see one that had been off road for a day.

[Bigrig]

Personally i would ditch the k&n filter on a 4wd.
They block up quick enough on the street i would hate to see one that had been off road for a day.

X2 - got one, tried it out, and ditched it a couple of months later (a few weeks ago). Clogs up unbelievably if you don't have a dust catcher thingymabob on your snorkel ... now back to normal paper filter ...

[Ben-e-boy]

I have 2 K&N's one clean ready to go in and one filthy dirty ready to come out

[Bigrig]

I have 2 K&N's one clean ready to go in and one filthy dirty ready to come out

Stop being such a boyscout (be prepared)!!! lmao

[LittleJohn]

cliff, do you use any 2 smoke oil in your fuel?
just asking as i do, and its great , but when i slip and too much goes in the mix,
the fuel consumption is absolutely rife,
i can visually see the fuel guage drop !!

[HammerBuilder]

Personally i would ditch the k&n filter on a 4wd.
They block up quick enough on the street i would hate to see one that had been off road for a day.

Yep they certainly do get dirty heaps but at least you know they are working, I clean mine bout every 5000k's with oil change but if in extreme dusty place i run a filter over top of snorkel saves the main filter heaps then if camping just wash it in afternoon trow it back on in the morn does the trick.
Apart from this yes it will use a little more fuel as now the tailshaft has to turn 4.1 times to do the same as the old 3.9 I know it dosent sound like much but you should have better power n towing.
As for heating just like others have said & also make sure you have the heater on & bleed all the air out of cooling system
Cheers n see how you go n please let us know how you go as others may need same info....

[billyj]

the porblem alot of people dont see with a k&n style filter is that being oiled and so close to the maf over time the hot wire on the maf gets a oily coating that affectes how it reads the incoming air

[kiwijase]

ive also read that somewhere billy.

[Robo]

Quite common yet overlooked causes for excessive fuel on efi cars are.
Engine not reaching the correct operating temp or fluctuating from cooler or incorrect thermostats.
02 sensor needs replacing usually 70 thousand k's max then bin it.
Bad cats honeycomb melted over.
Afm needs cleaning.
Engine fault codes.

x2.
these are all thing needing attention before going any further

[Robo]

the porblem alot of people dont see with a k&n style filter is that being oiled and so close to the maf over time the hot wire on the maf gets a oily coating that affectes how it reads the incoming air

x2.
ditch the oiled air filter.
it is a common problem, in all forms of motor sport.

[cliff]

The K&N is cleaned at least every month, depending on how much off-road work it gets.

I didn't think that I would need to change the gear drive on the speedo, I didn't have any dramas after the 285's went on, and the 4:11s would only bring the gearing back to a more stock setting anyway.

I will hit the MAF with some carby cleaner and see how it goes.

I will be booking into my mates workshop next week to spend some serious time and money on the ol girl, so we'll see how things pan out after that.

[Robo]

Do not use carby cleaner use maf cleaner.
it is different.
carby cleaners most,( should) have a dry lube in em, use that and you coat/seal the maf.

[97_gq_lwb]

I didn't think that I would need to change the gear drive on the speedo, I didn't have any dramas after the 285's went on, and the 4:11s would only bring the gearing back to a more stock setting anyway.



I was just thinking it may be whats affected your fuel economy.
Most ecu's go into a leaner fuel mode when not under load this is usually according to several factors.
Speed vs throttle position being one of them.
So if the diff ratio is changed it will have an affect.
The only way to really see if this is happening is by data logging it .
Ecu talk or something similar Maybe nissan consult

[RustyNav09]

i am just bumping an old thread so i dont create yet ANOTHER thread on fuel consumption.

i myself do not have a patrol but my brother does and i have been on this forum for a little while. I am asking this fuel consumption quesions for a work mate of mine. He has a 2002-04 GU 3.0L Patrol and he is having fuel consumption issues. i dont know kms on car or how its driven but im pretty sure its like any old generation. What i am trying to find out for him is why he is getting poor economy when the car is empty, but when the car has a 18ft van loaded it gets great economy and is a dream to drive? anyone got any ideas? i was thinking injectors but that wouldnt explain it when it was loaded.

thanks