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| MrNutter |
Posted - 27 Jul 2011 : 08:40:45 AM
I've been getting bad fuel economy out of my V6 VN for awhile now, about 400km out of a tank (city driving). I decided to do something about it so I put in a new fuel filter, O2 sensor & as much as I don't believe in additives, used a bottle of injector cleaner. I did each thing seperately so I could see which one made the biggest difference after a full tank of fuel. After the O2 sensor was changed my economy got worse, down to about 300km per tank city driving. This was not the result I expected so I reset the ECU according to the instructions on this website. It seems to have made no difference. I did notice when I reset the ECU though that the revs didn't drop at any point like I expected them to, if anything they rose after about 10 seconds. I tried doing another reset but didn't worry about revving to 3000rpm, I just let it idle for a couple of minutes then took it for a drive. Still no joy.
It seems to run fine but the economy is terrible. I've eliminated fuel leaks because I can't see or smell any petrol. There is something weird going on though as the gauge will drop substantially after the car has been parked for several hours. For example if I park the car with the needle bang on the half a tank mark & leave it overnight, I will go back the next morning & the needle will be 2-3mm above the next mark down, even after a belting on the gauge.
The gauge waves around a little but seems accurate. It's says full when the tanks full, half when it's half full & empty when it's empty. I'm at a complete loss to explain it & more importantly, fix it.
Anyone got any ideas? |
| 3 L A T E S T R E P L I E S (Newest First) |
| VNGRPA |
Posted - 01 Aug 2011 : 8:15:34 PM
I'm not to shore on that mate as i don't use mine so i cant tell, other wise i would take mine off and see what happens for you but maybe someone else on here can help you with that one ,
however in the past i have been told that you shouldn't plug them up wrong other wise it will cause problems,
good luck anyway mate hope you get it sorted out |
| MrNutter |
Posted - 30 Jul 2011 : 07:43:07 AM
Thanks for the reply VNGRPA.
It's not the plugs, it got a new set of Bosch Platinum about 2 months ago. I pulled them anyway & they are good & gapped correctly (1.5mm).
The exhaust system from the manifolds back was knackered so I replaced that about 6 months ago. After crawling round under it last night it all seems like it's still fine.
The vaccuum hoses seem the most likely culprit to me as there was a couple that I couldn't get the right hose for last time so I had to sleeve the existing broken hoses together with larger diameter hose. It's the 3 short hoses at the top of the black semi-cirle thing attached to the filler neck that all go into the plastic T-piece that I couldn't replace. I think I've done a pretty good job sleeving them & am fairly sure that there wouldn't be any leaks but I'll try & find the right diameter hoses so I can replace them properly anyway. I replaced the hoses one at a time so I could copy the order they were in aside from the 3 coming from the top of the tank which I had to do all at once. If I mixed the two smaller ones up & connected them to the wrong sides of the black semi-circle canister on the filler neck, would that possibly cause my problem? |
| VNGRPA |
Posted - 27 Jul 2011 : 1:50:43 PM
after reading what you have done so far witch all sounds great by the way ,first thing i would do would be to change the spark plugs ,check all the hoses coming out of the petrol tank and check to make shore your cat converter is in good condition
by checking the spark plugs you will be able to see or smell if the car is running rich (hence using more fuel) with resetting the ecu it would make no difference if the spark plugs are no good as it would tell the ecu your not getting enough fuel
with the hoses for the petrol tank by checking them you will eliminate any vacuum leaks you might not be able to smell it witch would make you think there's no leaks
and the cat converter - this could be on its way out if your car has been running rich it will have a big affect on blocking it if it is starting to get blocked the engine would have to work harder to get the air out the exhaust witch would use more fuel
hope that helps |
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