[rberg89]

Hi,

I used the jb4 for a few years on '11 335xi. It started throwing 2C57 Boost/Vacuum leak code with limp mode / half engine light. Removing the jb4 gets rid of the limp mode. I want to be able to hook up the jb4 again.

I have inspected hotside and cold side and don't have a boost leak. I replaced my boost solenoid and vacuum lines since someone mentioned that. But what's interesting is that when I connect the jb4 and start driving the car (even when car is warm), I can tell there's a lack of power, and as soon as i hit maybe 3.5/4k RPM the limp mode kicks on.

I tried logging today and connecting to the jb4 with my laptop worked okay (can see rpm etc responding in the app) but once I tried to Start Logging, the app became unresponsive. I tried again with the same result. Windows 11, so maybe thats it?

Anyway i've had the jb4 off for almost 2 years and am kind of frustrated / near resignation with this and wondering if anyone experienced similar. I don't think the jb4 is totally toast because i can connect to it and see changing rpm etc.

Ground is good (wired a new one after some issues with the ground on the shock tower bolt) and tested with multimeter, fine. I used to have methanol so i have the FSB box attached but don't plug it in.

recently changed plugs, coils, low pressure fuel pump, boost solenoid and vacuum lines, (have metal chargepipe with o-ring). and i did not mistakenly plug the MAP piggyback into the MAF.

Appreciate any advice

[slow35xi]

I had really similar issues and ended up uninstalling my jb4 literally today. Fixed all my problems. My MHD is coming tomorrow and I’ll try that instead.

[oVeRdOsE.]

what version you have?
what firmware?
what option can you change?


the big issue with jb4, there's no clear guides and no 'dummy' options or preset flashing options.

people having issues often got wrong firmware, wrong options, wrong maps, etc...
in example, on my jb4 (latest version with bluetooth), more than half of the user settings I dont know what they means, there's no info online and you can mess with it...

Sad they didnt come with a more robust way to avoid messing it up. MHD wins there.