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Chris28

Poor MPG 540i

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33 minutes ago, Chris28 said:

 

I’ve been using the trip computer for the MPG. I rarely let the tank go to empty so I haven’t had the chance to check it the old fashioned way. Are the trip computers prone to being inaccurate? 

 

The only way to really know your true mpg is to zero the trip and fill up, then calculate it at next fill up, if you started this thread based on your OBC reading then you actually have no idea what it really is!

 

BTW - my OBC is wildly optimistic on mpg, it thinks mine does around 30mpg but it actually does low 20s most of the time!

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12 hours ago, BarryM said:

 

The only way to really know your true mpg is to zero the trip and fill up, then calculate it at next fill up, if you started this thread based on your OBC reading then you actually have no idea what it really is!

 

BTW - my OBC is wildly optimistic on mpg, it thinks mine does around 30mpg but it actually does low 20s most of the time!

 

Yeah I will have to wait and see what figure I get whenever the tanks next empty. Though I’m still gonna do the vacuum leak test later today as the idle seemed a little rough when I started it earlier. 

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Tank doesn't need to be empty. Just brim it and zero trip. Then when you next fill it 1/4 tank whatever note the litres and mikes and do the maths. 

 

More you do it the more the pump cut out factor is reduced. 

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On 26/01/2019 at 20:28, NWJW said:

 

  I would echo the advice on checking it's getting up to temperature, if it's running cold it'll drink fuel. 

 

Edit, INPA will show you exactly how hot/cool the engine is running too and very nice motor by the way! :)

 

On 26/01/2019 at 10:33, grapefruit said:

Have you checked the thermostats - via the hidden menu - to make sure it's getting up to temperature?

 

Ok I checked the temperature via INPA. Here’s what it said she’s sitting at, after I let the engine warm up for about 20 minutes.

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41279D8E-B7D8-4122-A212-2A1D020ACB6B.jpeg

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 ^^^ It's definitely getting up to temperature seeing as the car will have a 102'c themostat, the lambda values look ok to my untrained eyes too. :? 

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Okay so I’ve done a real mpg calculation. The results aren’t good. Averaged 15.7mpg. Looks like the trip computer is pretty accurate. 

I’ve noticed a small pool of oil under the car recently. So I’m thinking the 2 could be connected. I can’t see where the leak is coming from when I have a look under the hood. I also had my mechanic check for oil leaks but he said he couldn’t see anything either. But there was definitely oil leaking from it today, you could see it clearly as the ground was wet.

I had the common manifold gasket changed a few months ago during its first service. Any other common oil leaks I should check? 

 

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Sure it's oil rather than fuel its leaking?
Anyway, those lambda values look lean. I don't know what logic the bmw ecu has but if they are constantly in that 0.1v range then it's not right.

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3 minutes ago, jonbill said:

Sure it's oil rather than fuel its leaking?
Anyway, those lambda values look lean. I don't know what logic the bmw ecu has but if they are constantly in that 0.1v range then it's not right.

 

Ok thanks! So do you reckon it’s the sensors that are faulty or it’s something else causing them to read high?

Also the leak could totally be fuel, that would explain why I seem to spot it whenever it’s wet. It simply evaporates too quickly when it’s dry and I don’t see it. So I’m guessing fuel filter?

 

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1 minute ago, boiliebasher said:

Hmmm..... Sounds like you may have a fuel leak some where which would explain the poor mpg.... Can you smell petrol when you lift the bonnet or generally around the car?

 

No I’ve never smelt fuel. It sometimes smells hot, if you know what I mean. Especially if I’ve just floored it. I thought the smell could of been oil leaking and burning on the manifold of something. 

The leak looks to be from right under the engine. So probably not the fuel filter. 

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Ah ok. Generally a fuel leak you can usually smell. But not always the case. I still wouldn't rule it out as a possibility though. Would explain a few things.

 

The "hot" smell could be something as simple as a rocker gasket. Not too much to worry about there. Easy/cheap enough to replace.

 

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I think it would be good to get it up on a lift somewhwere with the engine running to see if you can see whats leaking.

As for the o2 sensors, I'd do a bit of live monitoring.
It's normal for some Ecus to cycle between a bit lean and a bit rich to 'watch' that the o2 are working correctly. So you should see them cycle between 0.1 and maybe 0.9.
If it is constantly at 0.1 I think the ECU would be be trying to add fuel to make it richer. But I doubt fuel trims can add enough to get your fuel economy.

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4 minutes ago, jonbill said:

I think it would be good to get it up on a lift somewhwere with the engine running to see if you can see whats leaking.

As for the o2 sensors, I'd do a bit of live monitoring.
It's normal for some Ecus to cycle between a bit lean and a bit rich to 'watch' that the o2 are working correctly. So you should see them cycle between 0.1 and maybe 0.9.
If it is constantly at 0.1 I think the ECU would be be trying to add fuel to make it richer. But I doubt fuel trims can add enough to get your fuel economy.

 

Live monitoring, as in, rev it for a bit and see if they move? Is it strange that both of them are low? I was thinking that maybe the sensors are ok but something else is wrong and its causing those readings? 

As for the leak, it's booked into the mechanics tomorrow. I put a tray under the car today to see what landed on it. Its definitely oil. So hopefully just a rocker gasket or something. 

 

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Live monitoring, as in, rev it for a bit and see if they move? Is it strange that both of them are low? I was thinking that maybe the sensors are ok but something else is wrong and its causing those readings? 
As for the leak, it's booked into the mechanics tomorrow. I put a tray under the car today to see what landed on it. Its definitely oil. So hopefully just a rocker gasket or something. 
 
Yeah, drive around a bit and have some one watch those values.

If they are permanently low, I'd be inclined to suspect the sensors. They don't last for ever.
(although I would expect an EML, but not based on any knowledge of this engine! Hey ho)
If you can easily get at the spark plugs, it would be a useful check to take one out and check the colour of the tip to see whether it is burning a decent mixture.

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it is a petrol car and 4 litres engine

what more do you want?

come to the bright side... choose diesel 3 litres and enjoy 4.7 l per 100km

Edited by gine39530d

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19 hours ago, gine39530d said:

it is a petrol car and 4 litres engine

what more do you want?

come to the bright side... choose diesel 3 litres and enjoy 4.7 l per 100km

  

 And have a car with an engine that isn't as powerful, has much worse power delivery, doesn't sound as nice, doesn't rev as highly, isn't as smooth....

 

....... I should add I quite like the m57 lump (had a 330d for a while) but the only advantage it offers over the m62 is fuel consumption IMO.

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i got badly hurt by petrol back in 2015

had saab 95 and went on cross europe trip from Estonia to spain malaga

 

Holland france and germany killed me

prices were 1,67 euros per litre of benzine

 

and on a full tank of 80 litres i barely managed less than 800 on highways

 

since then now i am permanently traumatized and stay away from benzine

still i am suffering PTSD

remember it like yesterday

terror attacks in paris

burger king in holland

porn show in Amsterdam and ganja

 

+*******

and effin prices... still cry till this day

*****

Edited by gine39530d

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On 2/2/2019 at 11:14 PM, NWJW said:

 ^^^A  2001 car won't have an inlet air temperature sensor, the maf takes care of all that on later cars. 

 

It has AIT.  Look at the log.  Within spec too.

 

Lambda reg. is fine at 1.0.  But you have a multiplication of 0.6.  You have a leak somewhere.

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9 hours ago, adam- said:

 

It has AIT.  Look at the log.  Within spec too.

 

 

  

 Early non-vanos cars have an air inlet temp sensor, it clips into the front of the air box, later vanos cars (which the op has) have what looks like a provision for the sensor on the air box but it's blanked off. As said, this function was integrated into the mass air flow sensor on later cars and as you say, on the op's car it seems to be doing what it's supposed to be doing. :)

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Ok I have an update. The leak turned out to be oil from the rocker covers. Although the main gasket had been recently  changed, the little gaskets for the bolts weren’t. They where rock hard, I’ve now had the all gaskets changed properly.

If this had caused a vacuum leak then hopefully this will improve the mpg! I filled the tank tonight from empty, so I will be able to work out the new mpg in a week or so. Fingers crossed it’s been improved!

I will also get the car linked up to the INPA at some stage to see if the readings are now different.

I’ll keep you all posted.

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