[Colef30]

Hey guys, I was going to fill up my typical blend of 4 gal e85 mixed with 91. (FBO N55 ewg MHD 2+ e20) when I did I pulled out of the station and started my usual log after I fill up I noticed a distinct power cut with some slight stuttering/ light popping noises out of the exhaust. I didn’t throw any codes nor did I pick any up on mhd. I was a bit scared to do a full log so I did kind of a baby one. I believe it to be the hpfp due to my rail pressure not looking too great, compared to previous logs. Typically I fill my 4 gal blend and switch off each other tank to 91 to clean out the fuel system while switching tune to 91.

Attaching some logs below of normal vs today any input is greatly appreciated.https://datazap.me/u/colelindsay/log...a=4-19&mark=65

https://datazap.me/u/colelindsay/fue...og=0&data=4-19

[thejeremyman9]

Originally Posted by Colef30

Hey guys, I was going to fill up my typical blend of 4 gal e85 mixed with 91. (FBO N55 ewg MHD 2+ e20) when I did I pulled out of the station and started my usual log after I fill up I noticed a distinct power cut with some slight stuttering/ light popping noises out of the exhaust. I didn’t throw any codes nor did I pick any up on mhd. I was a bit scared to do a full log so I did kind of a baby one. I believe it to be the hpfp due to my rail pressure not looking too great, compared to previous logs. Typically I fill my 4 gal blend and switch off each other tank to 91 to clean out the fuel system while switching tune to 91.

Attaching some logs below of normal vs today any input is greatly appreciated.https://datazap.me/u/colelindsay/log...a=4-19&mark=65

https://datazap.me/u/colelindsay/fue...og=0&data=4-19

I think you linked the same log twice?

[Colef30]

Ah yes love that here u are. https://datazap.me/u/colelindsay/log...og=0&data=4-19

[thejeremyman9]

Originally Posted by Colef30

Ah yes love that here u are. https://datazap.me/u/colelindsay/log...og=0&data=4-19

There is only a very slight dip in HPFP pressure which would not cause what you described. You can also see that your fuel trims are still negative indicating that you did not have a fuel supply issue. You typically need sub 1000psi to start having fuel supply problems and be considered a HPFP "crash". Are you sure you just didnt hear that before the fuel was mixed? Did you add the E85 first? Did the problem go away after driving a little?

[Colef30]

It could be that I typically drive pretty easy for the first 5 mins my log was prolly 10mins after filling up. Maybe it could be mad sensor I’m going to try to clean it and see if that helps it definately felt like a bit of a stutter gonna do another log right now.

[Colef30]

Mass airflow sensor cleaned and retuned stutter is completely gone thanks for the input!much appreciated.

[thejeremyman9]

Good to hear, read my thread on datalogging if you want to learn some more and be able to dig into your own logs: https://f30.bimmerpost.com/forums/sh....php?t=1732327

[Colef30]

Originally Posted by thejeremyman9

Good to hear, read my thread on datalogging if you want to learn some more and be able to dig into your own logs: https://f30.bimmerpost.com/forums/sh....php?t=1732327

Thanks for being a big help on the forums my man.

[johnung]

Originally Posted by Colef30

Hey guys, I was going to fill up my typical blend of 4 gal e85 mixed with 91. (FBO N55 ewg MHD 2+ e20) when I did I pulled out of the station and started my usual log after I fill up I noticed a distinct power cut with some slight stuttering/ light popping noises out of the exhaust. I didn’t throw any codes nor did I pick any up on mhd. I was a bit scared to do a full log so I did kind of a baby one. I believe it to be the hpfp due to my rail pressure not looking too great, compared to previous logs. Typically I fill my 4 gal blend and switch off each other tank to 91 to clean out the fuel system while switching tune to 91.

Attaching some logs below of normal vs today any input is greatly appreciated.https://datazap.me/u/colelindsay/log-1637623977?log=0&data=4-19&mark=65

https://datazap.me/u/colelindsay/fuel-pump-going-out?log=0&data=4-19

Tip: BMW uses a split gas tank so putting fuel in the tank doesn't easily mix it to a consistent percentage of ethanol. I find that it helps to drive slowly around the gas station parking lot making alternating left and right turns to slosh around the full in the tank. I have a dash mounted Zeitronix ethanol gauge and that seems to work best.

[thejeremyman9]

Originally Posted by johnung

Tip: BMW uses a split gas tank so putting fuel in the tank doesn't easily mix it to a consistent percentage of ethanol. I find that it helps to drive slowly around the gas station parking lot making alternating left and right turns to slosh around the full in the tank. I have a dash mounted Zeitronix ethanol gauge and that seems to work best.

It's funny because i do this after my car has been sitting for more than a week incase there is any separation. Also, always add the ethanol first then fill up with the gasoline.

[Colef30]

Originally Posted by johnung

Tip: BMW uses a split gas tank so putting fuel in the tank doesn't easily mix it to a consistent percentage of ethanol. I find that it helps to drive slowly around the gas station parking lot making alternating left and right turns to slosh around the full in the tank. I have a dash mounted Zeitronix ethanol gauge and that seems to work best.

Y’all the mvps of the forums much love to y’all more knowledge every day due to y’all

[Colef30]

And just like clockwork the sound is back again I noticed now it’s only happening at idle and not while driving super wierd “thump thump” sounds that happened every 30 or 40 seconds going to run another log later today. Doesn’t happen at all in sp+ mode when I’m getting on it either.

[Colef30]

Sounds like a slight pop that happens in a rhythmic set of 2 pops.

[thejeremyman9]

Are you running an oiled air filter?

[Colef30]

Currently running stock air box.

[Colef30]

Afr jumps a tiny bit when the pop pop happens

[thejeremyman9]

Originally Posted by Colef30

Afr jumps a tiny bit when the pop pop happens

This is likely an effect not a cause. A misfire will cause a lean spike because of the unburned O2 in the exhaust.

[435gc]

Leaky injector?

Try taking a log at idle to capture maybe.

[Colef30]

I’ll try that was out of town now I’m back I was thinking maybe injector issue although all 6 were replaced in the last 10,000 miles so it seems unlikely will post up log later today.

[Colef30]

After car sitting for 2 days it runs fine again I was thinking could it possibly be unburnt gas from burble in my exhaust all of my parameters were looking fine and I took it on a short drive all the way up to temp and it disappeared again. Very puzzled at the moment.

[Colef30]

Going to let the car sit and pull plugs to check for leaky inj.

[Colef30]

My stft also seems to bounce a lot under boost from -5 thru -7 very quickly