Siemens MS41 - Running lean but lamba reading rich

Hi everyone,

I'm running into some strange issue.

Car is a Euro BMW E36 328i, car was mapped to E85 in 2020, car was running great from what the owner says, in 2023 he wanted to put a Eaton compressor, and a LINK Ecu. Car was running but mapping was never finished since compressor broke, Owner put back everything to stock ( even ecu ) , car never runned good from then.

I'm using RomRaider with openMs41 définition files, and MS41 flasher.

Car was brought in for a E85 remap ( Owner tought the old ecu was fryed and buyed a new one, the old one was in fact not fryed )

With the old ecu car is running super-lean (not even starting if car was warmed up). Found car was having a bad pressure regulator, and a dead lambda sensor.

Lambda sensor are titania type, Replaced the broke one with a new one, all of the two sensor are giving resistance like it should.

BUT

The 2 lambda sensor are reading rich, even when engine is lean ( done the test, changed the STFT LTFT limit to -80%, Ecu lean out the mixture till it stall )

Car isn't at the moment road capable so unpossible to try during various load and rpm for the moment )

When giving gas and letting the rpm go down, ecu is cutting fuel ( has it should ) and at this moment lambda are reading lean ( like it should )

What can cause a titania lambda to read rich even when it's lean, to the point of stalling the engine ?

Thank for your help

Are you sure it is selected in the ECU software, and correctly wired?

This may be of interest - https://secure.lambdapower.co.uk/TechNotes/Tech-7.asp

Hello,

Thanks for your reply

Wiring loom is stock and was checked, even in case of wire inversion of the sensing element, it will change nothing for the ecu since it output a resistance.

As far as I know, all ms41 ecu use titania sensor, so ecu configuration isn't in the scope for the moment.