[whoismorggan]

Trying to smoothen out my rolling pulls. When accelerating just a hair from a cruise, the engine feels like it's stuttering/misfiring and causes vibration in the frontend.

I've already replaced all spark plugs and ignition coils. Car has 83,000 miles. What should I check next? fuel injectors?

I'm currently running MHD 93 OCT Stage 2 with catless DP, BMS intake, and VRSF chargepipe.

[Liandri]

I assume the CEL isn't on? Can you scan the car for pending codes? Can you reflash the same map and see if it goes away? That's a few things you can do to start the diag process, it will rule some stuff out. If it goes away and slowly comes back the car could be learning it back in

[whoismorggan]

Originally Posted by Praetor353

I assume the CEL isn't on? Can you scan the car for pending codes? Can you reflash the same map and see if it goes away? That's a few things you can do to start the diag process, it will rule some stuff out. If it goes away and slowly comes back the car could be learning it back in

No CEL. I haven't scanned for codes yet.

I'll check for codes and reflash to see if that helps. Thanks!

[Liandri]

No problem. I just saw your build thread. Was the stuttering always there or introduced after a certain point? Are you confident in all the work that was done/did you do it yourself? (possibility of rechecking the work might be needed but I would expect a code from something if the error were bad enough to cause the motor to stutter)

Vibrations from the engine also need to be narrowed down. These motors are very smooth but engine mounts could be going bad especially with all the extra power. I still have yet to figure out what the stock mounts can handle, if they're hydro type mounts, and how long they last with so much more power going through the motor. In other makes of car its popular to get rid of hydraulic/oil dampened mounts because while they're great at removing the NVH from motor to chassis they often fail quicker than straight rubber mounts and much quicker if they're being thrashed outside of their power handling range. But again I don't know anything about these mounts specifically and it's on my list of things to look into, just a thought with your mileage


Edit- you said 40-60% throttle? Or is in the very low range/tip in?

[whoismorggan]

Originally Posted by Praetor353

No problem. I just saw your build thread. Was the stuttering always there or introduced after a certain point? Are you confident in all the work that was done/did you do it yourself? (possibility of rechecking the work might be needed but I would expect a code from something if the error were bad enough to cause the motor to stutter)

Vibrations from the engine also need to be narrowed down. These motors are very smooth but engine mounts could be going bad especially with all the extra power. I still have yet to figure out what the stock mounts can handle, if they're hydro type mounts, and how long they last with so much more power going through the motor. In other makes of car its popular to get rid of hydraulic/oil dampened mounts because while they're great at removing the NVH from motor to chassis they often fail quicker than straight rubber mounts and much quicker if they're being thrashed outside of their power handling range. But again I don't know anything about these mounts specifically and it's on my list of things to look into, just a thought with your mileage

It's been an issue for as long as I can remember. I purchased the car back in April of 2019 and the charge pipe blew and was replaced that same month. After that I installed a JB+ module and Injen intake so it wasn't stock for long.

I'm not sure the "vibrations" I mentioned are from engine mounts. It's more likely a side-effect of the misfiring I think. The car is smooth in any other scenario

[XutvJet]

At what rpms are you feeling this and which gears? I'm assuming you've got an 8at and are holding the gear when doing this.

[Dylan86]

Possible boost leak? May be the spark plug gap, who knows. Best to log each cylinder and watch what's happening.

[whoismorggan]

So I just did some pulls in Sport+ in 6th gear, rolling at around 80mph at 2k to 3k RPM. It feels like a completely different car, no stumbling, misfire or anything. Smooth as butter.

It seems that it only happens in 3rd-5th. I wonder if it's a tuning issue?

[whoismorggan]

Originally Posted by XutvJet

At what rpms are you feeling this and which gears? I'm assuming you've got an 8at and are holding the gear when doing this.

No specific rpm. Yes 8AT in manual mode holding gears

[XutvJet]

Originally Posted by f20two

No specific rpm. Yes 8AT in manual mode holding gears

With your mods, the driving situation you're describing, and assuming the typical 35-50 degree winter weather of NC right now, the DME may be combating a high-load situation and as a result, you feel some vibration as the DME compensates.

You indicate that you're going 40-60% throttle in Sport+ mode at a 2,000-3,000rpm range and in a taller gear like 3rd and above. 40-60% throttle in Sport+ (i.e., Sport throttle setting) is more like 60-80% full throttle as the throttle ramp up is much quicker in the first 1/2 of throttle travel and there isn't much throttle left above that point, especially when compared to the more linear Comfort throttle settings (Comfort, Traction, and DSC Off modes). The Sport throttle also manipulates the electronic wastegate which in turn greatly increase turbo response which then quickly changes A/F ratios, timing, and so on. Since the conditions are cold, this ramp up is even quicker because the air is so dense with oxygen. When you've got mods that reduce turbo backpressure, add a lot more boost/timing, and improve breathing, the DME has to be hyperactive as it tries to make sense of what is going on all the while trying to keep the motor together.

Going heavy throttle at a low rpm (i.e., below 3500rpms), in a longer and taller gear, teamed with a turbo, can lead to a very dangerous detonation condition known as Low Speed PreIgnition (LSPI). This condition can lead to very severe super knocking which is hell on the rod bearing and ringlands. Many turbo motors, especially modded ones, have died as the result of LSPI. It's not as common in BMWs and other German makes thanks to their complex safeguards and generally more robust internal parts, but with lots of mods, it's possible that the safeguards can't keep things in check. The vibrations you're feeling could be the DME fighting this situation.

My recommendation would be to:

1) Try the Stage 2 91 tune but still run 93 octane and see if it helps.
2) Stop doing doing your pulls below 3,000rpms and stop using heavy throttle in the taller gears. If you need to pass, pick a deeper gear and get the rpms up.
3) Consider throwing the BMS intake in the trash and go back to stock or use a closed airbox setup if you must have an aftermarket intake. Open element intakes cause nothing but trouble and don't make any useful power.

[whoismorggan]

Originally Posted by XutvJet

My recommendation would be to:

1) Try the Stage 2 91 tune but still run 93 octane and see if it helps.
2) Stop doing doing your pulls below 3,000rpms and stop using heavy throttle in the taller gears. If you need to pass, pick a deeper gear and get the rpms up.
3) Consider throwing the BMS intake in the trash and go back to stock or use a closed airbox setup if you must have an aftermarket intake. Open element intakes cause nothing but trouble and don't make any useful power.

Thanks for all of the info!

2) Happens in the upper RPM range too, just not as prevalent.

3) Regarding the BMS intake -- I was experiencing the same behavior with the stock airbox as well.


I'll flash STG2 91 and report back soon.

[XutvJet]

Originally Posted by f20two

Thanks for all of the info!

2) Happens in the upper RPM range too, just not as prevalent.

3) Regarding the BMS intake -- I was experiencing the same behavior with the stock airbox as well.


I'll flash STG2 91 and report back soon.

Hmmm...are you sure it's not just the driveline squirming with all the soft mounts, especially in the rear end? I can notice some vibrations in my 2016 M235 with a catted DP and Dinan Stage 2 piggyback but it's the rear frame and differential squirming around in their mounts from all the torque and the grip of the tires.

[whoismorggan]

Originally Posted by XutvJet

Hmmm...are you sure it's not just the driveline squirming with all the soft mounts, especially in the rear end? I can notice some vibrations in my 2016 M235 with a catted DP and Dinan Stage 2 piggyback but it's the rear frame and differential squirming around in their mounts from all the torque and the grip of the tires.

I guess I shouldn't have used the word "vibration"...

It comes from the front of the car, and it definitely feels like engine misfire/stuttering. I can hear it too, like the engine is breaking up while I accelerate and it's not a smooth pull.

I have never had problems with traction [xdrive]

[cooolone2]

If you aren't logging your engine then all you're doing is guessing! You need to log what's going on so trims, timing, throttle, iat, etc., can be seen. If it is misfiring, there'd be codes, or pending codes if intermittent. No codes? Then it's probably knock which is not good to have or keep repeating unless you want to lose a piston, etc.

So start logging and see what's up...

[whoismorggan]

Did some logging today. cooolone2 (or anyone else that has experience) - does anything look out-of-wack here?

- https://datazap.me/u/f20two/3rd-4th-...og=0&data=3-13
- https://datazap.me/u/f20two/3rd-5th-...og=0&data=3-13
- https://datazap.me/u/f20two/4th-5th-...og=0&data=3-13
- https://datazap.me/u/f20two/5th-gear...og=0&data=3-13

[MechEngineer]

Originally Posted by f20two

I guess I shouldn't have used the word "vibration"...

It comes from the front of the car, and it definitely feels like engine misfire/stuttering. I can hear it too, like the engine is breaking up while I accelerate and it's not a smooth pull.

I have never had problems with traction [xdrive]

So I actually had a similar issue in the past (stuttering at high load low RPM) and it turned out that it was my transfer case causing the issue. The clutches weren't engaging properly which caused that stuttering similar to what you described.

I ended up draining and refilling the transfer case oil (lifetime fluid my ass) and it completely fixed the issue. You can get the oil from fcpeuro for like $35.

[whoismorggan]

Originally Posted by MechEngineer

So I actually had a similar issue in the past (stuttering at high load low RPM) and it turned out that it was my transfer case causing the issue. The clutches weren't engaging properly which caused that stuttering similar to what you described.

I ended up draining and refilling the transfer case oil (lifetime fluid my ass) and it completely fixed the issue. You can get the oil from fcpeuro for like $35.

Hmmmm this is the first I've heard of transfer case issues. I hope mine isn't beginning to fail. Thanks for the info

[whoismorggan]

Originally Posted by f20two

Hmmmm this is the first I've heard of transfer case issues. I hope mine isn't beginning to fail. Thanks for the info

Today I decided to try out xDelete and my issues have disappeared. I think you were right, MechEngineer - it was the transfer case.

It feels night/day better. Accelerating from a standstill is a lot smoother, accelerating while in 3rd-5th gear is amazing -- no stuttering or choppiness, and the car feels nimbler in the frontend.

[MechEngineer]

Originally Posted by f20two

Today I decided to try out xDelete and my issues have disappeared. I think you were right, MechEngineer - it was the transfer case.

It feels night/day better. Accelerating from a standstill is a lot smoother, accelerating while in 3rd-5th gear is amazing -- no stuttering or choppiness, and the car feels nimbler in the frontend.

Another victim of the lifetime oil...glad I could help

[Liandri]

Originally Posted by MechEngineer

Another victim of the lifetime oil...glad I could help

Heh lifetime means lifetime of the warranty, but they don't tell you that. Changing all driveline fluids every 30-40k results in happy ownership and long lasting components. This should be at the top of everyone's to do list before tuning. I changed the rear diff oil on my 2016 with only 20k on the whole car and it looked like garbage. Did the trans right after bit hard to tell with the 8hp fluid as it's fairly dark looking when new

[BMWBLUEM235_]

Originally Posted by f20two

I guess I shouldn't have used the word "vibration"...

It comes from the front of the car, and it definitely feels like engine misfire/stuttering. I can hear it too, like the engine is breaking up while I accelerate and it's not a smooth pull.

I have never had problems with traction [xdrive]

Originally Posted by f20two

I guess I shouldn't have used the word "vibration"...

It comes from the front of the car, and it definitely feels like engine misfire/stuttering. I can hear it too, like the engine is breaking up while I accelerate and it's not a smooth pull.

I have never had problems with traction [xdrive]

same

[PghBMW]

Originally Posted by f20two

Trying to smoothen out my rolling pulls. When accelerating just a hair from a cruise, the engine feels like it's stuttering/misfiring and causes vibration in the frontend.

I've already replaced all spark plugs and ignition coils. Car has 83,000 miles. What should I check next? fuel injectors?

I'm currently running MHD 93 OCT Stage 2 with catless DP, BMS intake, and VRSF chargepipe.

What plugs did you go With? I know this is probably not going to get solved here without experiencing it. Sometimes when I'm WOT it feels like the trans can't keep up with shifting and it's hesitating to accelerating. I was coming back home last night and was at 65-70 and hit the gas and the car went to accelerate and stuttered a little bit then accelerated. I have an xDrive car.