[E91 Hoarder]

My average mileage is stuck at 6mpg. After resetting it almost immediately goes back to 6mpg and stays there.

Has anyone encountered something like that? Any ideas where to troubleshoot?

2006 325i, no idrive, MT.

Thanks!

[tlow98]

How far is your commute? How many miles do you average every time you start the car?

[E91 Hoarder]

Originally Posted by tlow98

How far is your commute? How many miles do you average every time you start the car?

Doesn’t matter the distance; easy or hard on the throttle, it is always 6mpg

[E91 Hoarder]

Any ideas folks?

[eljay]

Does the range calculate "properly"? Is it showing miles left approximately assuming 6mpg or does it show it what you'd usually get with the corresponding fuel level remaining?

Have you scanned the car for any codes? I would start there.

Also, found this that may be useful to try:
https://www.1addicts.com/forums/showthread.php?t=320316

[E91 Hoarder]

Originally Posted by eljay

Does the range calculate "properly"? Is it showing miles left approximately assuming 6mpg or does it show it what you'd usually get with the corresponding fuel level remaining?

Have you scanned the car for any codes? I would start there.

Also, found this that may be useful to try:
https://www.1addicts.com/forums/showthread.php?t=320316

The range, instant gauge, average speed all seem to calculate properly. When tank is full, it shows over 430 miles range and low fuel warning at around 50miles.

No codes related to the issue, I scanned.

Thanks for the link - I'll take a look.

[tlow98]

What is your actual mpg when you calculate actual miles driven/gallons used?

[E91 Hoarder]

I did the miles/gal manual calculation, and the actual is around 21mpg.

Also, per 1er post, I don't think the correction factor is a solution for my case.

How does fuel metering work in our cars?

[lookalikehuuh]

I thought there is a part of the calculation that goes thru the fuel regulator.

I did notice when I replaced my fuel regulator the MPG calculation somehow appeared to update at a different rate than my original regulator that had 200K+ miles on it.

[E91 Hoarder]

Originally Posted by TerminatorStout

The injectors are calibrated to have a certain flow rate. They are also controlled by the DME to open and close. The DME knows exactly how long it pulses each injector and it keeps track of it. It is constantly tracking these numbers and adding them up. It knows that at a certain flow rate, and a certain amount of time, will give the volume of fuel used. This is how it knows how much gas you have used. There really is no other way that I know of..

Now with that being said, there is a chance that these calculations, perhaps fuel flow rates are determined by fuel pressure measured at the fuel regulator in the N54 application, I can't tell you for certain, but I doubt it.

If you experienced what you said above then you (I dont want to open a can of worms here) had a problem with either your fuel pressure, electrical connection to it, or the fuel pressure was being reported incorrectly. I still find it perplexing to think the DME is actually calculating a flow rate based upon fuel pressure, usually it is a calculated CONSTANT.

I didn't want to do a bunch of math and more typing so i searched around on google to find an example of this to explain it to you. Here it is :

"4x 270cc/min injectors, time interval 1sec. 60 mph cruise. 60mph is 1/60th of a mile per second, or 96 kph is 0.026666 km/sec. Injector open time would be about 100 milliseconds in each second. Fuel used = 4 x 270/60 x .100 = 1.8 cc. US gall (const 0.064) = 0.0018 x 0.264 = 0.0004752, imperial gall (const 0.22) = 0.0018 x 0.22 = 0.000396. US mpg (1/60) / 0.0004752 = 35mpg. Imperial mpg (1/60) / 0.000396 = 42mpg. Metric (no const required) 0.02666/0.0018 = 14.8 km/L or 6.75 L/100km.

There is always the possibility there is a mini ferris wheel in the fuel regulator that has little scoops on it, each scoop = a butterfly shot glass and it counts the scoops as they pass by. Just kidding

I forgot to add two things, I am still getting ahold of this e9x animal, so I could very well be wrong. And the other thing was you probably understand how the vehicle knows how far it has driven, it does the simple math on fuel volume used / distance driven to figure out your MPG

Thank you for thorough response.

The odd thing is that other indicators report correct numbers. I.e. instant mileage gauge seemed to be showing relevant mpg, as well as estimated range is also within the reason. Average speed also correct.

Can this be related to the speed sensor?