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Old 19-01-2012, 08:27 AM   #1
an10as
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Default AU3 excessive fuel use

Hi guys, all of a sudden my AU3 (4.0lt) is drinking like there's no tomorrow.
Have done 280kms from a full tank and it's on 1/4 tank already!
When I bought it just before Christmas I was getting 650-700kms a tank.
Doesn't seem to be running any different just drinking like hell. There's no fuel leaks.
Any idea's why it would?
Thanks , Dave

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Old 19-01-2012, 09:38 AM   #2
Mr Hardware
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Default Re: AU3 excessive fuel use

Ok so fuel guages lie
are you running your aircon?
when was the last time you gave it a good servicing?
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Old 21-01-2012, 01:23 AM   #3
an10as
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Default Re: AU3 excessive fuel use

Quote:
Originally Posted by Mr Hardware
Ok so fuel guages lie
are you running your aircon?
when was the last time you gave it a good servicing?
Fuel guage ok. I filled up yesterday and it took 61lts.
Yes running a/c everyday lately
Service? Like what what kind of things?
Just dont know why it would suddenly drink so much
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Old 21-01-2012, 10:06 AM   #4
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Default Re: AU3 excessive fuel use

O2 sensor. try replacing that see what happens.
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Old 22-01-2012, 12:48 AM   #5
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Default Re: AU3 excessive fuel use

The most common causes of sudden fuel consumption are air filter, o2 sensor, MAP sensor (also runs like crap), and a blocked exhaust. Try those and see what happens. Probably wouldn't worry about replacing the MAP sensor as you'd know all about it if it was U/S
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Old 23-01-2012, 01:36 PM   #6
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Default Re: AU3 excessive fuel use

Shouldn't the warning light come up on the dash if it was the 02 sensor, MAP etc?
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Old 23-01-2012, 02:02 PM   #7
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Default Re: AU3 excessive fuel use

High fuel pressure will also cause this eg fuel regulator blockage.
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Old 23-01-2012, 02:38 PM   #8
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Default Re: AU3 excessive fuel use

Quote:
Originally Posted by an10as
Shouldn't the warning light come up on the dash if it was the 02 sensor, MAP etc?
Wish it was that simple. I don't think the AU has a "check engine" status lamp?
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Old 23-01-2012, 03:03 PM   #9
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Default Re: AU3 excessive fuel use

Agree with the above. 02 sensor would be the first thing I would replace. Then I would look at blocked cat converter if the 02 sensor is a no go.
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Old 28-01-2012, 12:08 AM   #10
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Default Re: AU3 excessive fuel use

Ok will do thanks guys. When I filled it last I put Shell 98 in to see how that goes. Gone just below 3/4 now and done 180kms. Been driving it a bit like a grandma on valium though lol.
I wonder if I had bad fuel, the fuel use went bad after I filled at a roadhouse in Kaniva, or could have been Nhill, cant remember, in Vic.
Also got the back loaded with work gear and roof racks and ladders on. A/C going everyday too.
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Old 28-01-2012, 10:18 AM   #11
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Default Re: AU3 excessive fuel use

Yeah so is the load a new thing too? One of the AU's biggest skills is aerodynamics (the same as a bullet) so ruining it with a ladder will see differences in fuel consumption.
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Old 28-01-2012, 10:23 AM   #12
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Default Re: AU3 excessive fuel use

Quote:
Originally Posted by an10as
Have done 280kms from a full tank and it's on 1/4 tank already!
that sounds normal (for the suburbs) to me, did you put a v8 in it accidentally? :P

yeh try exhaust areas first, then move on to the other suggestions
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Old 28-01-2012, 10:59 PM   #13
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Default Re: AU3 excessive fuel use

Quote:
Originally Posted by Mr Hardware
Yeah so is the load a new thing too? One of the AU's biggest skills is aerodynamics (the same as a bullet) so ruining it with a ladder will see differences in fuel consumption.
Wouldn't have thought it would make much difference around town at 50-80.
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Old 28-01-2012, 11:02 PM   #14
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Default Re: AU3 excessive fuel use

Quote:
Originally Posted by Professor Farnsworth
that sounds normal (for the suburbs) to me, did you put a v8 in it accidentally? :P
Country town, no traffic lights and not much traffic.
Yeh I think a V8 would get better economy than that. My inlaws 5.0lt VN gets over 700kms a tank easy.
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Old 29-01-2012, 12:50 AM   #15
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Default Re: AU3 excessive fuel use

his VN is a lot lighter

my AU V8 gets 650 on the highway, but about 400 in town
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Old 29-01-2012, 09:00 PM   #16
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Default Re: AU3 excessive fuel use

my vct xr6 sedan will easily do 700 k`s on a run for 60 litres, a little more if i treat it nicely, hot weather and loaded roof racks wont be helping your cause that`s for sure.
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Old 29-02-2012, 11:05 PM   #17
an10as
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Default Re: AU3 excessive fuel use

Well a bit of an update, It's getting a little better fuel wise around town, and also running better.
I replaced the old spark plugs with iridium ones and noticed a little oil leaking from the inlet manifold join to head so I checked all the inlet manifold to head bolts and most were not tight at all so I tightened them all up. A couple were bastards to get at to tighten too. It was sucking in unmetered air.
After this, the slight engine hunting under load diminished and the idle rose 150rpm initially but it was still sluggish under 3000rpm.

Next I put a new air and fuel filter in and I emptied the petrol out of the old filter. It was very brown and dirty there's crap in the tank.
It goes better again and more responsive under 3000rpm
When I get time I'll take out the tank and flush it out, also the fuel pump.
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Old 01-03-2012, 10:08 AM   #18
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Default Re: AU3 excessive fuel use

i knew a good servicing would fix most of your issues
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Old 02-03-2012, 12:30 AM   #19
an10as
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Default Re: AU3 excessive fuel use

Quote:
Originally Posted by Mr Hardware
i knew a good servicing would fix most of your issues
Yep just needs a little TLC
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