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nfitty4 nfitty4 is offline
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Posts: 8
Join Date: Aug 2021
Car: e92 335i FBO
Unhappy JB4 with Pump BEF - Fuel Trim Variance (Map 4) - 09-13-2021, 03:26 PM

Hi All,

Long-time lurker here on the forum. I have been able to troubleshoot all of my issues with existing threads until I ran into this and things have gone downhill. I finally resorted to making my first post.

I have a FBO 2007 e92 335i.

I recently installed new plugs, coils, new pre-*** O2 sensors, VC, VCG, OFHG.

Problem #1: Any WOT pulls result in being thrown into map 4 for the fuel trim variance. Occasionally a second bank misfire occurs if going to redline (cylinder is not consistent, but most times will be in cylinder 5). The car will pull into about 5000 RPMs and then the power saps, the noise changes, and I am thrown into map 4. Any partial throttle can throw me into map 4 with the same fuel trim variance notification, but it all depends on how much you get on the throttle.

Problem #2: The car now has some hesitation/surge problems from time to time (incredibly variable, some drives no problem, some drives I misfire on the second bank and have to clear out the codes). When present, it seems to get worse under light throttle load (cruising on the hwy at a constant speed for example).

I do (and have always) smell a consistent smell of fuel as if it's running rich, but I have always attributed that to the lack of cats in the car. The only code on startup I have is the 2C9F (Lamba probe heating behind catalytic converter #2).

When the misfires occur I have had a 2C7E (Lamba probe behind the catalytic converter, trimming control) and then the combustion misfire of whatever cylinder on bank 2).


Things that have been done:

Tried other spark plugs/ moved them around - the problem stayed in bank 2

Tried moving around Eldor coil packs - the problem stayed in bank 2

Replaced intake manifold gaskets (this came up in an old thread from Terry and I thought I would try it as it seems to be one thing that can cause fuel trim variance - No change in the problem

Replaced all injectors from FCP Euro for a new set of index 12's - no change in the problem

Reset adaptations in both MHD and on the JB4

Installed the most current JB4 firmware as well as the most current BEF map

Ran on map 0 and the problem remains


I have gone back and forth a bit with BMS. At first, they recommended a new LPFP, but from the logs, it looks like my PSI is in the healthy range. I am still sending map 1 logs at full throttle, but am pulling my hair out over here trying to diagnose this issue. I thought I would see if anyone can chime in.

Any thoughts or tips would be much appreciated.

Last edited by nfitty4; 09-13-2021 at 04:44 PM.. Reason: accuracy of recent replacements
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