Still bad fuel economy

[Karsten]

Hey everyone, i drive a VN V6 and am getting really bad fuel economy (200km from a Full Tank) according to my computer, i have tried the following but no difference:

- New Spark Plug Leads (Top Gun)
- New Spark Plugs (Bosch)
- New Oxyen Sensor
- New Coolant Temp Sensor
- Injector Cleaner
- Cleaned out Air Filter & Throttle Body
- SS Induction

Its really starting to annoy me and has been going on for a while now, if anyone could tell me the problem it would be much appreciated.
Thanks

[TVR-190]

check your fuel filter and breather hoses

[greenfoam]

ECU for sure, if not then fuel regulator, if it's not locking up the converter quickly as it warms then the ECU

[Dum*P*ster]

go to your local wreckers and find a VN ecu.
I got a mate who had the same issue, replaced EVERYTHING that causes bad fuel economy..And it was just the ECU had shit itself..

So he put $500+ down the drain,

[Karsten]

check your fuel filter and breather hoses

would my fuel filter be located underneath my car along the fuel rails? and what are breather hoses?
thx mate

[Karsten]

ECU for sure, if not then fuel regulator, if it's not locking up the converter quickly as it warms then the ECU

how do you know if the fuel regulator doesnt work? besdides the bad fuel economy of course, deap idle for example?? i read theres not much to go wrong with fuel regulators though.

[Karsten]

go to your local wreckers and find a VN ecu.
I got a mate who had the same issue, replaced EVERYTHING that causes bad fuel economy..And it was just the ECU had shit itself..

So he put $500+ down the drain,

ahk thx for that mate, good to see im not the only 1 lol. doesnt worry me too much i guess the parts your mate replaced would of been better for his car in the end

[Dum*P*ster]

where abouts are they located? thx mate

I no VP series 2 have a breather on the right hand side back, just in the wheel arch.. directly goin to the Fuel Tank

[Karsten]

I no VP series 2 have a breather on the right hand side back, just in the wheel arch.. directly goin to the Fuel Tank

are you sure its the breather hose? ive heard a few different things, not to sure which it is lol, are they parts hard to replace?

[Dum*P*ster]

Im pretty sure it is, someone posted a pic of what it is not long ago, tryin to find it now

[Dum*P*ster]

BAH! I FINDED IT! lol

http://images.google.com.au/imgres?i...icial%26sa%3DG

It's actually linked to this website

[alex2_s]

also keep in mind, is performance affected at all or just fuel economy? its possible to over-compensate for loss of performance by more throttle = more fuel used...

if so check things like the engines compression to see if you're not doing up an essentially dying motor, also no obvious restrictions to efficiency, dragging brakes/wheel bearings etc? motor gets to correct temp ? (thermostat), vacuum leaks somewhere?

super-slipping auto trans?

fuel pressure regulator is also a good possibility as mentioned...

oh and you mentioned the 200km to a tank being recorded by a computer, is this accurate? i assume this is backed up by a crude measurement/guess by resetting the tripmeter when filling up and seeing how far you can go...

[88GreenVN]

Check calibrations of the trip computer. 625 is the factory number for distance and fuel flow.

VN L3 Calibration - How To!

[greenfoam]

ecu

[88GreenVN]

Yep I bet it's the ECU too - but while your checking things on fuel ecconomy - may as well check the calibrations of the trip computer too.

[Karsten]

also keep in mind, is performance affected at all or just fuel economy? its possible to over-compensate for loss of performance by more throttle = more fuel used...

if so check things like the engines compression to see if you're not doing up an essentially dying motor, also no obvious restrictions to efficiency, dragging brakes/wheel bearings etc? motor gets to correct temp ? (thermostat), vacuum leaks somewhere?

super-slipping auto trans?

fuel pressure regulator is also a good possibility as mentioned...

oh and you mentioned the 200km to a tank being recorded by a computer, is this accurate? i assume this is backed up by a crude measurement/guess by resetting the tripmeter when filling up and seeing how far you can go...

I dont believe the cars performance has been affected, just the fuel economy, although i have only driven my VN so i wouldnt be 100% sure on how there meant to go, plus i tend not to boot my car as much, because it would kill me in petrol.

Checking things like the engines compression, wheel bearings and vacum leaks i am not to sure about (not that mechanically minded) but if you or any of the other JustCommodore members could give me instructions on how to check/ replace these things, would be much apreciated.

Also after each full tank of filling up (50L Tank) i reset my trip computer and compare the two receipts from my previous fill up, i thin from my last fill up i used an average of (21L/100km)

[88GreenVN]

I'd start with the ECU - $50 from a wrecker - would pay for itself in 2 weeks

if it was wheel bearings causing that much fuel the car would hardly move and stop when you took your foot off.

Regulator - maybe. Fuel filter - maybe.

It's the ECU that controls the air/fuel mix and if it thinks the engine is cold - it shoves in mega fuel. If the wire is damage between the sensor this may be the issue too.

[levymetal]

edit: something is wrong with my reading skills

[Karsten]

I'd start with the ECU - $50 from a wrecker - would pay for itself in 2 weeks

if it was wheel bearings causing that much fuel the car would hardly move and stop when you took your foot off.

Regulator - maybe. Fuel filter - maybe.

It's the ECU that controls the air/fuel mix and if it thinks the engine is cold - it shoves in mega fuel. If the wire is damage between the sensor this may be the issue too.

good way to sum it up, apreciate it

[ahmedomnnea]

Hi mates,
I have a 2002 VX with a 3.8L V6 engine, and I am having the same problem with fuel consumption, I fill up about 60L and reset the trip computer and the Distance to empty reads 450Kms, and while I am driving I can see the instantanous ful consumption which varies between 6L/100kms to 15L/100kms, sometimes it jumps to 30L/100kms when I push the accelerator all the way down until my rpms gets to 4500 rpms which I do may be 5 seconds in a month!!, but here is the problem:
when I fill up and reset the trip computer I should be getting 450kms to a tank0 (which is also not that good) but it runs out of fuel after 230kms and I need to refuel or it would die on me.
please helpppppppp.

[88GreenVN]

Hi mates,
I have a 2002 VX with a 3.8L V6 engine, and I am having the same problem with fuel consumption, I fill up about 60L and reset the trip computer and the Distance to empty reads 450Kms, and while I am driving I can see the instantanous ful consumption which varies between 6L/100kms to 15L/100kms, sometimes it jumps to 30L/100kms when I push the accelerator all the way down until my rpms gets to 4500 rpms which I do may be 5 seconds in a month!!, but here is the problem:
when I fill up and reset the trip computer I should be getting 450kms to a tank0 (which is also not that good) but it runs out of fuel after 230kms and I need to refuel or it would die on me.
please helpppppppp.

Change your o2 sensors if you have not done so already.

[ahmedomnnea]

I didn't check the o2 sensors yet but if the o2 sensors are faulty shouldn't I be getting different (higher) readings for the fuel consumption in the dash trip computer, it shows an average of 10.5L/100kms but what I am getting actualy is about (20-30)L/100kms.
please, I need help.

[Lost_Pete]

Mine is bad because the odometer only works part time.

[levymetal]

I didn't check the o2 sensors yet but if the o2 sensors are faulty shouldn't I be getting different (higher) readings for the fuel consumption in the dash trip computer, it shows an average of 10.5L/100kms but what I am getting actualy is about (20-30)L/100kms.
please, I need help.

not necessarily. the computer could be off due to many reasons. you've already been given help - the o2 sensor is the first thing to change when you have bad fuel economy. change that, and report back with your new economy. also change air filter if it's been a while, and check tyre pressures. pretty cheap start