VN V6 - BAD fuel economy

[dazzla]

Hi,

I've got a VN V6, series 1 which is getting about 5.5km per litre (is about 18L/100Km).
Engine power is OK, the idle is a little rough sometimes (occasionally misses) - but all in all it seems to be running fine apart from the fuel issue.

About a week ago, I had the injectors cleaned (which seemed to improve response).
About a month or two ago, I replaced the oxygen sensor.
Neither of these made any difference to the fuel consumption.

I can notice a bit of a petrol smell when I get out of the car after driving for a few minutes. I'm not sure if this smell is comming out of the tailpipe or is there is a leak somewhere. - I cant see any leaks in the engine bay, but have not checked under the car.

Does anyone have any suggestions?

thanks,
dazzla

[immortality]

change the fuel filter first. check all the flexible fuel lines around the tank. these are getting old now and are probably presished by now. clean the TB and IAC valve and reset the idle. do a search, plenty of threads here on how to do this. a good service never hurts.

[dazzla]

Sorry, prob should have said I changed the fuel filter, did it last week when i had the injectors cleaned. Also changed spark plugs.

The flexible bits of hose either side of the fuel filter did not seem perished, maybe this weekend i'll change them anyway. - same for the flex lines to and from the engine fuel rail.

I replaced the ignition control module and harmonic balancer earlier this year.
About 3 years ago I replaced fuel pump too.

The TB and IAC probably need cleaning, but could they really be responsible for such excessive fuel consumption??

[Shortstuff]

It made a difference to my fuel consumption when I cleaned the throttle body/ IAC valve. It was using about 16 or 17l/100km before and went down to about 14. Made no difference when I changed my oxygen sensor.

The Fuel Pressure Regulator might be something to look at as well.

[88GreenVN]

The temp sensor could be playing up - uses more fuel if it thinks its cold.
What about the plugs & leads

[dazzla]

forgot to say that i changed the temp sensor when i did the injectors and plugs.
- the old one tested ok, but for $17 ..
I changed all the flex lines, don't expect that to do much; they were all in good condition.

The pressure regulator is on my list of suspects, along with the MAT and MAP sensors - the gregorys mentions all of these.
I havent got a fuel pressure meter, might have to invest in one.
is the pressure reg cheap? if so i might just change it.
and if i get some time next weekend, i'll clean the TB - makes me wonder about the rest of the manifold if the throttle body can eat up a few litres per 100km..?

also, a friend of mine suggested the catalytic converter might be restricting the exhaust - tapping it makes a sound that certainly does not sound 'solid'. Does this sound likley?

[VNPOWER]

how long are you driving it for each day?

City or highway?
My normal average week is 10minute trips in city traffic and that = 200k's per tank.

Did a long drive today.. and got 432k's and a 1/4 tank left..


Another thing you should check, when you actually fill up how much are you putting in? When mine reads empty (Red) i only fit 30 litres in which means there is still over half left...

Which technically means i should be able to get over 500k's if i just keep driving it while reading empty..

Just consider these things before you go crazy trying to work out why its drinking..

[dazzla]

I drive about 20k per day in normal traffic - Pretty much all my driving is in average suburban traffic, never peak hour.
I'm calculating my efficency based on what the bowser reads.

-So are you saying you get 200km per tank as measured by your gauge? which is 15L / 100km if your 'tank' is 30L? - In crap traffic, that's about what I would expect is normal.

I think I've already gone crazy trying to figure this out.
Always it work out at exactly 5.5km/L (18.2 L/100km), irrospective of driving style. And thats with 98 octane fuel too..

[VNPOWER]

my tank is 63L