Several issues... Related or not?

[nrp22101]

My 92 850i boggs down under load but only after the car warms up. I recently did a top end refresh and have a VERY slight intake leak confirmed by a smoke test. Took it to my local BMW mech and he was unable to read the codes and doesn't know why the reader was unable to connect. Oddly enough it worked once and only once. I feel like I'm throwing darts.
The one time he connected he was able to read the the mixture adaptation at idle was very high (see image) which is odd because at idle it purrs but under load drops to 6 cyl.
Diagnosis would be much easier if I can connect the code reader.
Any thoughts on why I can't connect or or reason for these symptoms?
Appreciate any help...

Thanks


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[Timm]

The adaptations show that you have a slight vacuum leak on Bank 2 - and a bigger one on Bank 1 - but at part throttle everything is fine. So, that is not the cause for dropping a bank when the engine is under load. More likely to be plugs, HT leads and the Cylinder Identification sensor.

[nrp22101]

The adaptations show that you have a slight vacuum leak on Bank 2 - and a bigger one on Bank 1 - but at part throttle everything is fine. So, that is not the cause for dropping a bank when the engine is under load. More likely to be plugs, HT leads and the Cylinder Identification sensor.

Thanks Timm, I'll turn my attention to those ignition components first.
In your opinion, is the vaccum leak large enough to warrant resealing?

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[Timm]

I think I would investigate the 'running on one bank' problem first, and then take it from there.

[nrp22101]

Issue is resolved and wanted to post for inquiring minds.
Computer showed no codes so that was no help.
Technician started by testing MAFs, tried new ignition coils and inspecting leads, caps and rotors. All looked and tested fine. Checked all grounds and we'll were good. Next swapped FPRs- no difference.
Removed exhaust and I specters cats. Cats good. Drove it with exhaust off and car was still dropping a bank under load.
Head scratch.
Next, checked fuel pressure-all good at idle but checked pressure under load and noticed fuel pressure on 1 Bank dropped to zero. BINGO! Inspected fuel pumps and noticed a SLIGHTLY loose connection that turned out to be the culprit.
Car now hums and pulls like a freight train.
Case closed.
Thanks to all who chimed in with their expertise.

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[shogun]

congrats, good find, those are some of the difficult things to find out when it sometimes works and sometimes not. I just remember this case in 2011, it turned out the tab was broken on the 3-pin fuel pump power connector and the connector had worked its way loose a little. https://www.bimmerforums.com/forum/s...tranded-SOLVED