insanely Poor mpg

[VLN1SRZ]

hey guys so over the past couple of months my 1 series has had the worst gas mileage ever, feels like I'm driving a Hummer. when driving its cool and dandy, the mpg doesn't increase in city driving no matter how i drive but it doesn't drop.

But the minute i stop on a light or get stuck in traffic the number drops 0.1 MPG very rapidly 12.0........11.9.............11.8 etc. (currently sits at 9.2 and dropping). i know what you'll say its because the car isn't moving and fair point but when i move and look at my range maybe 15/20 kms have been slashed off during that traffic stop/idle. Car currently does 250KMs on 3/4 of a tank which is a big wtf

Dont know what to do, changed O2 sensor, changed valve cover, ignition coils, no CEL no codes. And it does the freakiest shit where it actually retains some gas range when i put the car in DS. So I'm beyond stumped tbh.

Thank you

[Thunderguts]

Are you actually putting that much gas in the car or could it be a bad sensor causing the mileage computer to mis-calculate?

Don't rely on the CEL. I assume you've plugged it into a decent code reader and pulled nothing?

[VLN1SRZ]

Originally Posted by Thunderguts

Are you actually putting that much gas in the car or could it be a bad sensor causing the mileage computer to mis-calculate?

Don't rely on the CEL. I assume you've plugged it into a decent code reader and pulled nothing?

I hope that's the case, just wont know what part to change, because I did change my low-pressure fuel pump when the issue first started.

[Thunderguts]

I assume you don't have a fuel leak, but that would be easy to detect. If you were burning that much fuel, you would smell it in the exhaust and I'm pretty sure it would throw a code. There's no way to combust that much fuel normally.

So I think you have a bad fuel level sensor.

[fotontom]

This may be a silly question, but have you actually calculated the MPG manually at a fill-up?