FBO M5->now "stock" drivetrain malfunction

[silverfoxS65]

Hey all - 2014 M5 - 63k miles
Car has been a FBO stage 2 BM3 car for approx 8k miles now w/factory spec plugs replaced at 50k by dealership before going stage 2

recently (this past weekend) I put OEM DP back on for state inspection, and flashed it back to stock tune
car drove fine for a day (trying to rack miles for inspection readiness)

next day when I went to build some boost - it just fell on its face at like 3k rpm in 2nd gear
did it a few more times after that almost sounding like it had a 2-step in it lol
and it just wouldn't let me build any power

eventually drive train malfunction and CEL and limp mode. pulled codes and it had like 30 of them - most of them associated with limp mode
it idled like it was a cammed LS motor - lol

reset codes and drove it nice and easy to prevent it cutting out and limp mode

i've been able to get it to consistently reproduce the issue without it totally shutting the car down in limp mode

i'm getting a crankshaft signal error (160020) along with some codes about blocking boost pressure (which makes sense if the car senses an issue)

question is...a lot of you say this symptom (drive train malfunction and engine cutting power) is new plugs...which i never put the .018-.020 gapped NGK's in cause it ran fine when i went stage 2 - so i get that
and maybe this is an opportunity to replace those now

but do you think crank sensor is bad or is it just getting a misread since the car is misfiring?

thanks for the help in advance

[technician117]

The stock map shouldn't cause issues obviously, so the next thing is to look at what was touched between good running and bad running. I would inspect the car in the area you just worked on. Maybe a DME bracket is loose or a ground is missing, etc. We've seen that trigger weird issues like this before. It's a simple/free check too.

[BB6]

Originally Posted by technician117

The stock map shouldn't cause issues obviously, so the next thing is to look at what was touched between good running and bad running. I would inspect the car in the area you just worked on. Maybe a DME bracket is loose or a ground is missing, etc. We've seen that trigger weird issues like this before. It's a simple/free check too.

He is right on, everything on your car is most likely fine since you had no issue before putting on the old stock downpipes. I have swapped out the downpipes a few times now and there are several things that can be forgotten to tighten down or make sure they are connected properly. Just go through everything on the car again and make sure everything is connected and tightened. I'm sure you will find something simple and it will be a sigh of relief.
By the way, are you using ISTA?

[silverfoxS65]

Replaced plugs with NGK and gapped to .022 last night. Drove it for like 10 miles with a few pulls.
Everything seems perfect.
Once I put catless DP I'll go back to stage 2

[BB6]

Originally Posted by thatorangem5

Replaced plugs with NGK and gapped to .022 last night. Drove it for like 10 miles with a few pulls.
Everything seems perfect.
Once I put catless DP I'll go back to stage 2

Makes sense. Some guys are running stock gap and stock plugs on Stg2, but I am sure there are variables why they can still run stock plugs/gap: fuel quality, elevation, variety of intake designs, etc.
Whenever I go back to all stock on my car I found out I have to go to stock plug and gap otherwise I loose power drastically from running rich or misfires. Then when I put the catless DP's back on and the STG2 tune back in I have to run the NGK colder plug gapped to .019 -.020 otherwise I get misfires. It's a pain, but its right for the car in my case. That's awesome you figured it out though. Guys chase these type of things for a long time to only find out it was something simple. Good work.

[apexlocator]

Originally Posted by BB6

Makes sense. Some guys are running stock gap and stock plugs on Stg2, but I am sure there are variables why they can still run stock plugs/gap: fuel quality, elevation, variety of intake designs, etc.
Whenever I go back to all stock on my car I found out I have to go to stock plug and gap otherwise I loose power drastically from running rich or misfires. Then when I put the catless DP's back on and the STG2 tune back in I have to run the NGK colder plug gapped to .019 -.020 otherwise I get misfires. It's a pain, but its right for the car in my case. That's awesome you figured it out though. Guys chase these type of things for a long time to only find out it was something simple. Good work.

Whats part # for these colder NGK plugs? where? thanks.

[silverfoxS65]

Originally Posted by apexlocator

Whats part # for these colder NGK plugs? where? thanks.

Originally Posted by apexlocator

Whats part # for these colder NGK plugs? where? thanks.

NGK 97506

[BB6]

Originally Posted by thatorangem5

NGK 97506

Correct. NGK SILZKBR8D8S (97506)