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Discussion Starter #1 (Edited)
I could not find a thread for this issue, so I am starting one in hope to find answers to my issue. Few days ago, as I was sitting in a traffic on lights, I casually played with the BC and got into actual consumption part of it. The thing is, it was reading incredibly high figures, fluctuating between 15-25 litres/100km. Now, I remember when I did this few months ago, it always showed around 1 litre on idle, in neutral. I started to notice it while driving, lets say I am coming to lights, I mostly downshift my way to 2nd gear and then disengage to neutral. When I do this, my consumption is super high, 25 litres showing at times. Its really weird, having a consumption like that when the engine is actually idling. Anyone got an idea what could be the cause ? Greatly appreciated.
I should also point out that consumption lately is on the rise, measuring by full tanks in the past months. It isnt much, but there is an increase for sure.
 

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When you're standing still your fuel consumption in mpg or km per litre, or litre/100 km, is infinite. Think about it....
 

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Discussion Starter #3
I know where you heading, but I was pointing at the fact that some time ago it was reading 2L actual consumption, now it does 20L.
 

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As long as you realise both are wrong. I can't remember if mine says 0 or 99.9, at idle when standing still, but they'd be wrong too. Most likely your body computer has slightly different firmware and/or integrates with the ECU differently. Which raises a question: have you done a proxy alignment with the new BC? is the odometer flashing?
 

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Discussion Starter #6
Nope, odo's not flashing or anything. Its just weird because lets say I am going down a hill using engine to brake, it reads 1-2L. While approaching lights at steady speed in neutral reads 20L.
 

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Its just weird because lets say I am going down a hill using engine to brake, it reads 1-2L.
Of ourse it would be possible for the ECU to be programmed to completely shut off fuel injection on the over-run, in which case the readout should display '0' (since on over-run there is no need to make any power at all). But it's my understanding that this isn't usually the case, i.e. that most ECUs are programmed to inject a small amount of fuel on over-run, to keep the O2 sensors and catalyitic converters hot, and something to do with reducing NOx. That is, there is some fuel wastage during over-run for emissions related reasons.

Regards,
John.
 

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Discussion Starter #9
I understand there is some fuel being injected there, but the point is that it has risen to 20L somehow.
 

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Mine says ----- when i stand still (idle)
Duh, yes, so does mine, now I think about it. It says 99.9mpg on the overrun, foot off the accelerator.

I've very seldom even looked at the 'real time consumption', as it's fairly useless except as ICE. I keep a record of what I put in the tank/cost/mileage, which gives true consumption.
 

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Discussion Starter #11
I, too, don't rely on the BC to show me the consumption.. I already said it in the 1st post that I count it with what I put in and how many km's I did. Maybe I can finally get an answer, on what could cause this ? Its been okay for more than a year, but now the cons. got worse and then I noticed this idle fluctuation.
 

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I waited off deliberately rather than jumping in as usual.

Consumption worse, fluctuation of idle are clues.
On my JTS, over-run sees MPG go very high but goes to "--.--" when stopped. I've not tried the metric display yet as I'm not going to subject the JTS to urban driving.

Anyway, it does sound a bit like injector spray patterns are a bit off. Can you give more info about use, driving habits and even the fuel you use please? Info about engine oil would be useful can can you please also go and smell the engine oil (strange request, I know but I have a reason).
What is the car's total distance covered and do you know of any non-routine maintenance which has been performed on the engine?
 

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I wouldn't use the computers fuel consumption data to diagnose anything. The numbers are junk! If you have actually calculated a decrease in fuel consumption my first guess would be a stuck open thermostat. It should be reaching 88 quickly and never dipping below this.
 

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Discussion Starter #14 (Edited)
Driving habits - home to work and vice versa - 20kms. Once or twice a week I do ~150kms. I would say 50/50 urban / A roads. I put 98 unleaded in the tank most of time. Oil changed less than 1k kms ago (Selenia Racing). It does drink oil a bit, but not huge amounts. I top up every ~300 km's with 100-300 ml depending on how much I trashed it. So around 1L / 1kkm. It had head rebuilt following a cambelt failure, it had injectors refurbished, and new cambelt that time. It happened 3 years ago, I got the car for 2 years now. The oil doesnt smell with petrol. The car has covered 170kkm. Maybe its worth mentioning that it still has original clutch, as my mechanic told me there could be some fluctuation caused by the clutch. But other than some squeeking when started in cold (And I mean winter cold, when its below 0), I and neither him could not notice any deviations pointing the clutch is bad.
 

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Discussion Starter #15
Regarding the injectors - don't think they are the culprit here. The idle rpms hold nicely, 850 while warmed up. Not experiencing any running or power issues. No misfires detected on diagnostics. But I am not taking this as a definitive that they are 100% in order.
 
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