[techy101]

tl;dr - Took it to a shop and they found that the tank was filled with ~90% water

I've got a question about bad gas or just really strange timing of another failure.

I recently flashed my 2009 335i from a Dinan stage 2 to MHD stage 1+ 91 octane map (I have the supporting mods) and have had no problems.

Earlier today I filled up with 93 octane from a BP station and, after about a mile the car started to stumble quite badly under light to moderate acceleration. I did not get a CEL but only drove a couple of miles home. I just pulled codes and got the following active codes.

* 29E0 - DME: Mixture Control
* 29E1 - DME: Mixture Control 2
* 2A2B - DME: Mixture Control

The internet seems to say that it's due to bad upstream O2 sensors, but having both banks at the exact same time would be very weird. I had also heard it suggested that there could be a large air leak somewhere?

As far as I understand it, there should be no problem putting 93 in a car with a 91 tune. So am I incorrect about that or is there a chance this is bad gas?
Is there a way to tell if the gas is bad and, if so, what's the best way to correct it?


Some additional information:

Plugs were replaced 7,000 miles ago with NGK 97968 (one step colder) gapped to 0.022" and all six coils were replaced with Delphi GN10571. The bank 1 upstream sensor was also replaced the same time.

Injectors are all index-12 as well; the three on bank 2 were replaced with new OEM index-12 about 3,000 miles ago, the other three were updated to index-12 about 60k miles ago.

The charge pipe is aluminum, not the factory plastic one.


Any help would be greatly appreciated.

For troubleshooting, are there specific sensors to monitor or other diagnostics to narrow this down? I know bad gas is exceedingly rare and unlikely, and I'm concerned that I'm too focused on that and not looking at everything else. But there's a darn strong correlation with the timeline.

[Sgop335]

Log is what is needed for diagnosis!

in cases like this a simple lambda regulation adaptation may help

[techy101]

So, I just tried to take it for a drive and log but the car no longer starts. Sometimes it will start to run then stall out again after a second or two, though that didn't happen in the attached video.

To my lay-person interpretation it seems like it's not getting fuel. I do have logs trying to start the car and am seeing rail pressure in the 2,300psi and lpfp pressures around 85psi during crank. There was also a very strange smell that I can't describe after cranking. It doesn't smell like gasoline, oil, coolant or anything else I'm familiar with. (I realize that's not particularly helpful)

Flashing the stock map did not change anything.

I uploaded a log to the appropriate thread, but will put it here as well to avoid linking between threads.

Log: https://datazap.me/u/techy101/crank-...&data=11-19-20

Video:
https://youtube.com/shorts/Gol7F0Bn5Dg

[Sgop335]

Wow it is strange. Any codes?
Could be pointing to bad gas especially if it ran well before w all same setup…

[techy101]

Originally Posted by Sgop335

Wow it is strange. Any codes?

I cleared them after the first two no-starts and none have come back.

[techy101]

I decided I was out of my depth and had it towed to a shop this morning out of an abundance of caution in case there were something really messed up with the gas and damage could happen by letting it sit in the car.

The shop got back to me and found that the gas tank was filled with ~90% water and 10% fuel. Which means that virtually everything that came out of the pump was water. I filed a complaint with the state commerce department (weights and measures people who put those stickers on the pumps) and tried to talk to the station but was told I'd have to wait until tomorrow morning to talk to the manager. Keeping lots of notes and having the shop save me a sample of what they pull from the tank.

They've got to drain the tank and put new gas in it to see if any other damage was done. I'm super glad I decided to send it in though and get that crap out of the tank immediately.

I can't even fathom how this happens.


People always swear they got bad gas and it's almost always a mechanical problem, but for once it actually was the gas lol

[Sgop335]

That is what i thought, and water being heavier gradually gave the fuel mixture codes then all water!
Agree not seen bad gas stories…what gas station, make sure this is compensated.
I would think other customers would have affected too

[techy101]

Originally Posted by Sgop335

That is what i thought, and water being heavier gradually gave the fuel mixture codes then all water!
Agree not seen bad gas stories…what gas station, make sure this is compensated.
I would think other customers would have affected too

I filed a report with the state weights and measures department about a suspected fuel quality concern and it turns out they take it very seriously.


They had an inspector at the station within three hours of submitting the form online. He did find water in the tank, pulled it from sale, and I will be getting a state report that I can use to go after the station to recover the tow and repair costs.

So, if this happens to you, immediately file a complaint with the state.