Stumbling, bucking and sputtering at low rpms and high gear ever since switching to e tune

colinod

Private
Aug 13, 2017
48
20
0
Ride
2007 e92 335
I have been having this issue ever since i switched to a full ethanol tune. I have a stage 3 bucketless setup, mmp port injection, 60# ls3 injectors, 6266bb, on3. manual boost controller

When i first switched to the e85 tune, i had a stage 2 pump and the port injection installed. when i am in a cruise, and sometimes from a standing start, the engine bucks and sputters whenever i get on the throttle. whenever i am cruising and i get on the gas, the engine will buck and sputter before it finally "gathers" itself and downshifts and accelerates. when my bucketless bracket and second walbro 450 came in, i wired it so that the new walbro 450 is the primary fuel pump and the older one i was already using in the stage 2 setup is the secondary one that turns on when i hit 15 psi. however this didnt change anything. i have a log of this happening. my tuner is confounded. to remedy i have tried, throttle body reset, lambda reset, lambda regulation reset, octane reset, new high pressure fuel pump, new index 12 injectors, some new revisions on the tune, same issue pops up.

runs fantastically with no timing pulls or throttle closure at WOT. this issue for some reason does not pop up when pulling a log for the tuner despite the fact that 2500 rpm is kinda of low for 3rd gear start on a non twin scroll setup.

it most often happens when i am cruising down the street at 35-45 mph in D5 and i give it about say 50% throttle to pass someone. the car will sputter for 2-3 seconds and then the downshift will occur and the car will run just fine like nothing ever happened.

knowing that the car does this when pushing the throttle when cruising in high gear, i started a log before i did just that

https://datazap.me/u/colinodon1gmailcom/when-car-bucks-under-moderate-throttle-high-gear

since im auto, i dont know whats making my engine do this instead of the auto merely downshifting and driving normally. i did get the transmission replaced before this tune, and it did not happen on my old pump gas tune from EMP
 
Last edited:

jyamona

Captain
Platinum Vendor
Nov 7, 2016
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Philly
Probably your MMP port injectors LOL. But seriously, disconnect PI and see if it still does it. Your STFT are like the rocky mountains, which absolutely should not be the case at that load request / pedal input.
 

colinod

Private
Aug 13, 2017
48
20
0
Ride
2007 e92 335
Probably your MMP port injectors LOL. But seriously, disconnect PI and see if it still does it. Your STFT are like the rocky mountains, which absolutely should not be the case at that load request / pedal input.

i am using 60# ls3 style from highperformanceinjector

i dont know what it could've been, my engine let go two days ago. cyl 6 is kaput, when i open the oil cap it looks like i have found cheech and chong's hiding spot. needless to say i will side with a new tuner after the new engine gets put in
 

pysical

Sergeant
Jun 16, 2017
352
76
0
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2009 335xi E90
Interesting. I have the same issue. And I am using the same injectors from HPI....

I may unhook the PI and see if it does the same thing. Didn't think about that.
 

Rob09msport

Major
Oct 28, 2017
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Monroe CT
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09 335i msport le mans 18 x5
I wonder if your number 6 pi was not firing properly you should try to fire injectors off car make sure you don't toast another engine