HELP - sudden loss of power with fuel reserve warning

[annesemmons]

2018 f80 m3 with a downpipe and pop tune.

I was pushing the car on the interstate going about 140 when my fuel reserve light came on and I immediately started losing power. The car slowly decreased speed and wouldn't rev passed 1500 rpm or go above 10 mph. The redline lights also set themselves to about 5000rpm and turned solid red (no yellow/orange).

I limped the car to a gas station and got gas, then when I turned the car back on it ran and drove fine. However, when I got home I noticed it was leaking some fluid (it looked/smelled/felt like water) but it was dripping at a pretty steady rate (about 1 drop per second). I unfortunately had to leave and couldn't look the car over in depth so it's just driving me crazy thinking about it.

I'm really confused what happened as the loss of power seemed completely electronic based on the fact that it happened simultaneously with the fuel reserve warning. I also had about 1/8 tank of gas left (50 mile range) so I don't think I was just out of gas.

Anyone ever have anything similar happen?.

[b_w.]

Not sure if it would happen as easily on the interstate but these cars have fuel starvation issues below a half tank on the track. At 1/8 tank maybe could have been possible hammering down the hiway....

[FRZN CS]

Completely stock 2019... I have about 25 miles left and had the same thing happen in sport plus, nothing simultaneously with the reserve warning, and I don't recall the same thing in economy. I thought it was just electronically governed to not starve it under hard acceleration (high fuel flow), as I assume you wouldn't want the fuel system to cavitate because it seemed to happen once I hit the same RPM range... but I wasn't about to do a scientific test to find out the limits.

No leakage though...

[annesemmons]

Hmm interesting. I dropped the car off at BMW for diag this morning but haven't heard anything yet. They seemed to suspect failure of the high pressure fuel pump based on what I told them, but they also said it's weird that the car never threw any codes. Also no explanation for the fluid leak...

[Soul Coughing]

Could have run the tank dry, car hiccups, goes into limp home mode. You don't turn car off until you fill it up and then car runs fine.

Considering you're from Florida and its humid, the drips you saw were condensate from the A/C running.

[annesemmons]

Soul Coughing I parked the car at the gas station and turned it off, then decided I wanted to get gas and turned it back on. It drove fine from the parking spot to the pump and that was before I got gas.

As for the leaking, I don't think it was AC-related because it was a pretty cool night and I had it turned way down. It was also dripping WAY more than I've ever seen it drip even on the hottest day running full blast.

I'm thinking maybe something exhaust related?

[b_w.]

Originally Posted by annesemmons

Soul Coughing I parked the car at the gas station and turned it off, then decided I wanted to get gas and turned it back on. It drove fine from the parking spot to the pump and that was before I got gas.

As for the leaking, I don't think it was AC-related because it was a pretty cool night and I had it turned way down. It was also dripping WAY more than I've ever seen it drip even on the hottest day running full blast.

I'm thinking maybe something exhaust related?

there are only a few things it can be...exhaust will leak water...it is the byproduct of combustion. Not uncommon for water to leak at connections or be blown out the tail pipes.

condensation off of your AC compressor which does drip when its running

engine or intercooler coolant

oil

fuel

my bet is it went into limp mode after being starved at full throttle and a low tank. Once you stopped the fuel pickup was good and the issue was gone.

How often do you look under your vehicle? there will usually be a puddle from the compressor and you just happened to be looking because of the issue.