Strange engine issue 2007 335i n54

bmwlover123 · 03-20-2018, 04:54 PM

Hello all. I'm having a "not so serious" issue with my car. When I'm going over 50-60 miles, when Im not accelerating or slowing down and keeping a steady speed, the car kind of increases the rev and comes back to normal every 1-2 seconds. It is like the car wants to speed up but realizes that I am trying to keep a steady speed and gives up. This happens every 1-2 seconds when I'm trying to keep a steady speed. When I'm accelerating, no problem.

Do you guys have any idea what might be the issue with my car? Thank you so much in advance. I appreciate your help

dsjr2006 · 03-20-2018, 08:53 PM

Are you saying 50 miles per hour or distance of trip?

What kind of transmission do you have?

How long has this been going on?

Any recent maintenance or repairs?

Any codes?

RocketSurgeon · 03-21-2018, 11:00 AM

Does the car actually accelerate, or is it just an RPM fluctuation. It kind of sounds like the torque converter locking and unlocking.
I think some data logging is in order to identify the cause of this.

bmwlover123 · 07-18-2018, 04:22 PM

Quote:

Originally Posted by RocketSurgeon

Does the car actually accelerate, or is it just an RPM fluctuation. It kind of sounds like the torque converter locking and unlocking.
I think some data logging is in order to identify the cause of this.

What tool can I use to log some data?

This issue also happens when I'm travelling with low rpm in sport mode, the car sometimes acts as if I removed my foot from the gas pedal for a split second and then pressed back on

RocketSurgeon · 07-19-2018, 02:32 AM

Personally, I would use INPA to read live data from the engine computer while someone drives the car in a manner that causes the behavior. See if anything weird is happening with sensor readings or actuator positions. Also read off live data from the transmission. Since you mention sport mode, you must have an automatic.
You can also reset adaptations to fix stuff like this.

03-20-2018, 04:54 PM	#1
bmwlover123 New Member 1 Rep 23 Posts Drives: 335i Join Date: Sep 2017 Location: binghamton iTrader: (0)	Strange engine issue 2007 335i n54 Hello all. I'm having a "not so serious" issue with my car. When I'm going over 50-60 miles, when Im not accelerating or slowing down and keeping a steady speed, the car kind of increases the rev and comes back to normal every 1-2 seconds. It is like the car wants to speed up but realizes that I am trying to keep a steady speed and gives up. This happens every 1-2 seconds when I'm trying to keep a steady speed. When I'm accelerating, no problem. Do you guys have any idea what might be the issue with my car? Thank you so much in advance. I appreciate your help
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03-20-2018, 08:53 PM	#2
dsjr2006 Captain 157 Rep 848 Posts Drives: '01 E39 540iA, '09 E90 M3 Join Date: May 2013 Location: Metro Detroit iTrader: (1) Garage List 2010 BMW 335i [0.00] 2001 BMW 540i [0.00]	Are you saying 50 miles per hour or distance of trip? What kind of transmission do you have? How long has this been going on? Any recent maintenance or repairs? Any codes? __________________ E90 M3 DCT LCI \| E90 LCI N54 M-Sport(retired) \| E90 Technical Docs download: http://j.mp/bmwe90docs *good read, very detailed.
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03-21-2018, 11:00 AM	#3
RocketSurgeon Lieutenant 264 Rep 459 Posts Drives: 2008 135i Manual, CBR650F Join Date: Jan 2017 Location: NC iTrader: (0)	Does the car actually accelerate, or is it just an RPM fluctuation. It kind of sounds like the torque converter locking and unlocking. I think some data logging is in order to identify the cause of this.
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07-19-2018, 02:32 AM	#5
RocketSurgeon Lieutenant 264 Rep 459 Posts Drives: 2008 135i Manual, CBR650F Join Date: Jan 2017 Location: NC iTrader: (0)	Personally, I would use INPA to read live data from the engine computer while someone drives the car in a manner that causes the behavior. See if anything weird is happening with sensor readings or actuator positions. Also read off live data from the transmission. Since you mention sport mode, you must have an automatic. You can also reset adaptations to fix stuff like this.
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