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Osiris Osiris is offline
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Posts: 4
Join Date: Jan 2018
Car: E89 BMW Z4 35i DCT
Default Z4 35i Over fueling and using way too much fuel - 01-25-2018, 07:34 AM

Hey guys,

I don't see an introductory section so I apologize in advance if an introduction is required on this forum before a post.

a small introduction. I have a 2009 z4 35i DCT sDrive.

Mods include:
charge pipe
large FMIC
*****ted *********
*****ted Exhaust
oil cooler
stage 2 fuel pump

Right down to my question.

I have been having very high fuel consumption ever since owning this car. I took ownership of this car in June 2017.

So far every single tank I get under 300km to a tank no matter how I drive. if I drive the car hard I get less than 250km to a tank if I drive and keep the car under 2000rpm to work and back everyday I get max 290km to a tank at a stretch.

So far I have tried the following to remedy the fix among different MHD maps.

1: JB backend flash via MHD
2: MHD stage 0 stock map
3: BMW stock map
4: MHD stage 2 91oct95Ron
5: MHD stage 2+ 91oct95Ron

I have changed one of my o2 sensors that was causing one of the banks AFR's to run lean

I have recently less than 500km ago had the car carbon cleaned via wallnut blasting

I have done 4 oil changed in the space of a month to get the oil perfectly clean

I have had brand new turbos fitted, new radiator, new coolant sensor.

The car has new injectors fitted around 5000km ago. Revision 12

I recently had *** foolers (Mini cats installed).

All of this has made zero difference. The carbon clean made the car run a little smoother and idle quieter. That's about it.

The car has a strong fuel small that actually burns my sinuses. my Previous car was a E46 330i and it had a nice smell to it while idling. This N54 Z4 is very strong.
I was thinking maybe its a leaky injector but from what I have read a leaky injector would cause a missfire and rough idle. my car is idling very smoothly so I don't know.

I did a MHD log with the MHD Stage 0 tune a night ago, Please could you guys maybe look through it and tell me if you notice anything obvious.
I had the mini cats fitted a week ago and I think they have caused a few issues with the AFR's so I am getting them removed tomorrow but I may be wrong as I am not very experienced at what these readings should be.


Please guys if you can let me know from that log if you see anything obvious please let me know.


No idea why its putting stars where I have listed my mods.

Last edited by Osiris; 01-25-2018 at 07:36 AM.. Reason: No idea why its putting stars where I have listed my mods.
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Osiris Osiris is offline
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Posts: 4
Join Date: Jan 2018
Car: E89 BMW Z4 35i DCT
Default 01-25-2018, 08:42 AM

Guys honestly why is it putting stars everywhere in my post???? The link isn't working as its replaced a bunch of text with stars....
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Osiris Osiris is offline
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Posts: 4
Join Date: Jan 2018
Car: E89 BMW Z4 35i DCT
Default 01-25-2018, 08:52 AM

Well I have tried to past the link many times now and it just puts a bunch of stars as above. not sure whats going on. Can't see if there are any forum rules that have some kind of weird clause that prevents links or words like d e c a t d o w n p i p e
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JuniorB JuniorB is offline
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Posts: 329
Join Date: Mar 2016
Car: 2007 e60 5 series
Default 01-29-2018, 07:37 PM

Awh man,you know emission stuff is frowned appon. This is BMS's forum, it's in there signature. Anyway, if your smelling raw fuel, your leaking and should strop driving the car. Put a gauge on the schrauder valve, and pressurize the system, see if the gauge drops
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General.Massacre General.Massacre is offline
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Posts: 108
Join Date: Sep 2017
Car: 2009 E92 335i DCT
Default 02-13-2019, 01:54 AM

Hi all.
I know the OP, and have assisted with Troubleshooting.

So far, the car still gets around 300km to a single tank of gas, but if the OP unplugs the vehicles Amp, then his fuel usage extends to about 450km to a single tank of gas.
any chance there is a possibility of electrical issues of thew amp linked to anything in the fueling system, maybe causing large draw or something?

Ive been googling, but either get Amp issues, or Fuel issues, never anything that is linked together.

Anyone had this before?
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NoQuarter NoQuarter is offline
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Posts: 72
Join Date: Jul 2012
Car: 2008 535xi
Default 02-14-2019, 12:34 PM

Unless you have traced where the fuel smell is coming from then any other troubleshooting should be postponed.

If the smell is that bad, then you need find the source then take it from there
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Dave @ BMS/Fuel-It!'s Avatar
Dave @ BMS/Fuel-It! Dave @ BMS/Fuel-It! is offline
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Posts: 4,201
Join Date: Apr 2014
Car: E92 335XI
Default 02-14-2019, 10:24 PM

Trace fuel smell

Also- we don’t use third party host sites- just upload the JB4 CSV direct to post


e92 AT 335xi 2.0
Doc Race Kit 6062
Fuel-It!Platinum DIY PI Kit + Stage 2BL
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