My 18is is consuming way to much fuel...

[bmwman91]

Makes sense, good call on testing at the DME. If the temp sensor is anything like the sender, the wires by the connector might be prone to breaking.

[MVincken]

but when the coolant sensor is broken, won´t the coolant gauge also give a bad value?

[5Toes]

^ no. there are two separate senders. one for the DME and one for the gauge.

[MTD]

So the car is back from the mechanic. The temp sensor was gone, so he put in a new one. Let's hope that was the problem! Filled a tank today, i'm gonna report in a week or so when i fill again and get the mpg calculation!

Also, thanks for all the tips guys!

[916e30Dave]

I'm interested to hear your results

Sent from my SM-N910T using Tapatalk

[word is bond]

Hey - any follow up on this? I've had a similar issue for while. Replaced the O2 sensor, but no difference...

[MTD]

Hey, sorry i forgot to mention the results.
So, last saturday i filled up again... and the results where disappointing. 22.5mpg. 1mpg of improvement, but that's probably cause i did a trip with 70kms of continuous freeway.

This problem is really annoying, and is driving me to bankruptcy. Filling the thank every 7 days, with the gas prices here in europe is insane.

Other suggestions as to what might the problem be?

[MVincken]

Strange, try to put on an emission tester, maybe the lambda sensor has gone bad.
No engine fault codes?

[MTD]

Strange, try to put on an emission tester, maybe the lambda sensor has gone bad.
No engine fault codes?

Emissions should be ok, it was tested the other day when i took the car to get inspected and certified to drive another year, at the inspection center

no fault codes

[MVincken]

hmm, yes i was more talking about percentage of oxigen in the exhaust gasses.

how is the rest of the hardware of the car?
try to jack it up and check if all the wheels run free
when is the last time you changed your motor/gearbox/diff oil?

[MTD]

Hardware is ok. All wheels are ok.
Oils have been changed about 1/2 months ago, almost after i bought the car

[d_elson0]

Alignment/toe/caster? Tire pressure. What wheels you have? Wheel bearings. Knock out the simple things first like prior posts mentioned. 21mpg still ain't too bad, but can be better

[MTD]

14" standard bbs wheels. They were aligned on a wheel house on the machine a week ago, they are alright. What does toe and caster mean?

i was really hoping to get better than 21mpg... Fuel efficiency was the main reason i chose the m42 over the other engines

[bmwman91]

21MPG is poop for these engines. Back in 2008-2009, I would get 32MPG when I was commuting and actually trying to get good mileage. That is 32MPG calculated by dividing the trip odometer by gallons at the fuel pump, so actual 32MPG.

For whatever reason, if I look at my mileage since about 2010, it just decreases linearly and nothing that I ever replaced or fixed ever really helped. I still have not put my new coolant temp sensor in, but it sounds like it might not be the issue. Readings from my wide-band O2 sensor seem to indicate that things are running properly at stoichiometric.

So, maybe it is in fact a dying diff or bad wheel bearings. Sadly, those are sort of expensive and involved to replace. I will be replacing all of those items in a month or two as part of my prep for autoX in 2016 (scored a Quaife 4.10 LSD on here a little while back!)...I will report back if it help anything in my case. The small case 4.10 LSD I have in there now makes a lot of noise.

[MTD]

I would get 32MPG

oh yessssssssss

please also report if you could fix the problem. I also intend to get new wheels maybe in the beginning of next year, but the diff was something i only was going to change more down the line. Hope that's not it..