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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > Regional Forums > UK > UK Technical Forum > Help..... E91 320D economy



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      05-18-2010, 02:25 PM   #155
SteveF1
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I understand what you're saying but the car did more miles to the gallon when I first bought it to what it produces now. As the car hit last winter the mpg dropped quite noticeably and I put it down to the low temps and the freezing winter we had. Now we are hitting summer the mpg hasn't really risen so thats were my problem starts, the fact the car did at one time have acceptable mpg and now it doesn't and I need to find the route cause.

I had a Golf R32 before this BM and it averaged 30mpg, 23mpg when worked hard. For a V6 to be comparable in consumption terms to a 2.0 litre diesel is in my view totally unacceptable in any driving condition or range.

After having the car spend more than three weeks (spread over past six months) in the garage fixing various things I have officially admitted defeat on this issue as I don't think BMW give a monkies and stifle their dealers when it comes to problem solving. There is a major over reliance on computer diagnostics as opposed to physical checks and that in my view has prevented my problems from being sorted.

BMW don't care.
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      05-18-2010, 02:37 PM   #156
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Quote:
Originally Posted by SteveF1 View Post
.... As the car hit last winter the mpg dropped quite noticeably and I put it down to the low temps and the freezing winter we had. Now we are hitting summer the mpg hasn't really risen so thats were my problem starts, the fact the car did at one time have acceptable mpg and now it doesn't and I need to find the route cause.
Excuse me if you have posted on this before, but have you had the 'running' coolant temperature checked? Or done so yourself, through the hidden menu? Make sure you are running around 89 - 90 degrees C.

EGR thermostats are a common issue.

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      05-18-2010, 03:05 PM   #157
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BMW may have checked it but they haven't specifically stated to me that the coolant temps were checked so I'm not particularly sure. How can I find out what the temps are running at, I do not have I-drive so can this still be done?

Forgive me but what is the EGR and what does this do and what are the common issues with it?
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      05-18-2010, 04:03 PM   #158
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I am getting 47mpg regardless of how hard I drive her!
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      05-18-2010, 05:33 PM   #159
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^ That's my problem right there.

Why am i not?
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      05-19-2010, 02:38 AM   #160
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Hmm for whats its worth I have a 116i courtesy car at the moment and average MPG (i reset it when I got the keys) is 19


Anyway, aside from that...

If BMW refuse to front the repair/investigation bill: What you have to consider is what cost those 4-7 mpg actually cost you per year of ownership in real world terms.

If your getting 28 mpg and do 10k miles a year then you are using 357 gallons of fuel. 1622 imperial litres which at 1.20 per litre is 1,946 per year on fuel.

If however you get 34 mpg which is a significant improvement, the figure is 295 gallons and therefore 1,609

This means if your going to keep the car an entire year further, its worth spending 330 approx fixing this issue - to BREAK EVEN. This is no net benefit. Only peace of mind that your MPG is better.

So as I'm only keeping my car another 15 months, and BMW have refused to replace the MAF so far - basically I feel like I have no choice but to put up with the MPG. The cost of replacing even just the MAF will be over 300. Its a 180 part and they'll want 2 hours labour. I can possibly get it done independantly and break even, but if I'm just breaking even I can't be bothered with the hassle. And furthermore to that, it might not be the MAF. It might be XXX other part. Black hole of money if I ever saw one.

Very frustrating but this is the realisation I came to. Basically it's not worth me worrying about this problem any more because BMW can't be bothered to help me with it.
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      05-19-2010, 03:22 AM   #161
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Hi

Just can't understand how the economy is so bad on your cars - after all the investigative work etc.

Have you guys contacted a "technical-type" person at BMW head office? I can't believe that your cars are unique - someone must have experienced the problem - maybe it's a "known" issue. If not, it should be.

Sometimes (with other products) you can get put through to an "anorak" who can answer your queries in a more forthright fashion than the Managers at the main dealers.

Maybe this is worth a shot as a last resort?

Jeff
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      05-19-2010, 03:24 AM   #162
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I am working on that very same premise Mega....

We do quite a few less miles per year than 10k though so my scope is reduced somewhat.

Im still reluctant to touch the MAF......I assume you have disconnected it etc and nted no difference?

Would you say that your motah is noisy at idle for example compared to another 3er?

I cannot escape the fact that 2 injectors showed as fault on my diagnostics session so i MAY take that hit and just do it.

They can be had for about 160 a pop.

If that does not cure it, im done.

JJ
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      05-19-2010, 06:02 AM   #163
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if your MPG is not improving much as the weather gets warmer then thats also pointing to the MAF. A lot of MAF sensors have the intake air temperature sensor built into them. If this fails then the ECU assumes a air temp value of -5C and fuels the car for these conditions. So in this warmer weather the ECU is over fuelling all the time.

I have replaced several MAFS over the years and always seen an improvement in MPG. They should be a service item in my book, replaced every 40K or less.

For driving to optimise MPG you are off boost most of the time and the MAF is the most important sensor for fuelling. Once the turbo is boosting the MAF is almost ignored and the MAP sensor takes over.

just my 2p........
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      05-19-2010, 08:06 AM   #164
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I've not tried disconnecting it. To be fair I'm almost 100% sure that its the MAF, but BMW just won't listen, and that "almost" part of me makes me not want to take the leap.

Furthermore I've got a mate who is a bmw technician, and he was fairly adamant it wouldn't be the MAF. And he gets annoyed at me for always researching everything online etc.. Like he knows better, except he doesn't know the answer.. so...

Sigh..
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      05-20-2010, 01:38 AM   #165
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You know Megs, 100 quid gets a MAF..........brand new.

http://www.airflowmeters.co.uk/

Those guys quited me 100 after taking my part number and they guaranteed a straight swap with no issues or my money back.

Its an easy job too mate.

Literally, 2 allen bolts (engine cover) and then 3 more (MAF) and a plug.




Might be worth a punt for a ton?

JJ
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      05-20-2010, 02:24 AM   #166
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I would - but Its been an expensive month.

Cheers for the info though
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      05-20-2010, 03:40 AM   #167
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Grim lad.....

Im just waiting for mine to break now ffs.

Jj
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      05-20-2010, 03:45 AM   #168
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Sorry lad, i was talking dick too.

It was http://www.airmassmeters.com/

They guy was called Paul and it was 143.




Jj
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      02-04-2011, 06:53 AM   #169
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jinjur and others, did you ever get to the bottom of these fuel consumption issues?
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      10-16-2012, 06:22 PM   #170
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So, guys, did some of you change the MAF ? I am having same issues with my fuel consumption. All termostats changed, EGR cleaned. I am having 27mpg with 33km/h average speed.

e91 m47n2 auto
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      10-19-2012, 03:30 AM   #171
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I have just increased my MPG while investigating a slight oil weep the other day:



Normally get 600 miles from 62 ltrs = 43.54 mpg, 138K, manual, re-mapped, both stats changed and don't drive it hard but normal drive to and fro work is very slow stop/start traffic. Next will be the MAF sensor.

The big plastic air pipe had a little hole in the bottom, dipping very small amounts of oil occasionally. Bought a replacement pipe and now seems a bit better. Doesn't lag as much now when pulling away and MPG on the OBC went up by 4, but haven't nailed a full tank yet. The MPG must of been effected as un-metered air was getting into the system, although not much air.

By the looks of it, the oil was coming from the small breather pipe and not the turbo seals as I couldn't see an oil around the blades. Just worried that the oil may build up in the bottom of the new pipe or get sucked through the turbo.

Also found a random hex bolt wedged in-between small brake pipes, not sure where it came from, looking at realoem it looks like hex bolts go with the turbo area but it doesn't show where, and its too tight to see where it lives. This had a turbo replacement before I bought it so maybe its came loose or one of them bolts you drop and use another one in its place.
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