[parkjake50]

Hi guys, I have been searching this for about few hours now but it seems like i can't really come down to an answer. :/
My car is a 2008 328xi AT. N51 71000 miles.

This is my daily. I have recently noticed that at a stop light, while holding the brake, my car would suddenly have shaking/ jerking sensations. RPM would idle around 700 but then it would drop to about 550 when it jerks. (only does this when in D).
I tried to scan the car with the Carly app and it doesn't show anything (no CEL).

I was wondering if anyone had this problem or know about this problem that could provide me some help as this is my daily and need this vehicle to finish my last 2 semesters of clinical rotations at hospitals around me (up to 1 hour of driving).

I would really appreciate it. Thank you.

[gbalthrop]

Originally Posted by parkjake50

...2008 328xi AT. N51 71000 miles.
...at a stop light, while holding the brake, my car would suddenly have shaking/ jerking sensations. RPM would idle around 700 but then it would drop to about 550 when it jerks. (only does this when in D). I tried to scan the car with the Carly app and it doesn't show anything [maybe Order an MRI then? ] (no CEL)...

I'm NOT familiar with Carly, as far as its capability to read Fault Codes or Parameters in the EGS (Transmission Module), but there MAY be more diagnostic information available connecting to the EGS with INPA or ISTA.

IF the issue ONLY arises when stopped with foot on brake in D, about the ONLY obvious prescription for the clinical symptoms presented is "Don't stop with foot on brake in D."

Since that is NOT realistic, the question becomes: what additional tests or diagnostics are indicated? If there was rough idle when in P, and NO Fault Codes or warning lights, that would suggest an air leak in the intake such as from a cracked Breather Hose between the Valve Cover and the Intake Manifold.

However if you ONLY get the jerking and idle speed change when in D (I presume same in DS or sport mode, or in any forward gear?), that is consistent with a torque converter issue. I'm curious if you ever feel a "bump" at the moment when, or within a second after, you stop at a light? There have been numerous reports of such behavior, and that seems to be related to torque converter function/ Dysfunction, where the transmission is NOT sufficiently and/or uniformly disengaged from the engine by the torque converter.

One test you might conduct is, with foot firmly on brake pedal, to lightly apply throttle so that idle speed per the tach is increased to 1,200 to 1,500 RPM, and see if the jerking is exacerbated, or diminished.

If all diagnostic testing I can devise suggests a transmission issue, since I have done most ALL my own auto diagnosis & repair, EXCEPT for AT, I would consult a specialist (Good local tranny shop). It is after all a GA6L45R GM transmission in 328xi.

Please let us know what you find & Merry Christmas!
George

[parkjake50]

Originally Posted by gbalthrop

I'm NOT familiar with Carly, as far as its capability to read Fault Codes or Parameters in the EGS (Transmission Module), but there MAY be more diagnostic information available connecting to the EGS with INPA or ISTA.

IF the issue ONLY arises when stopped with foot on brake in D, about the ONLY obvious prescription for the clinical symptoms presented is "Don't stop with foot on brake in D."

Since that is NOT realistic, the question becomes: what additional tests or diagnostics are indicated? If there was rough idle when in P, and NO Fault Codes or warning lights, that would suggest an air leak in the intake such as from a cracked Breather Hose between the Valve Cover and the Intake Manifold.

However if you ONLY get the jerking and idle speed change when in D (I presume same in DS or sport mode, or in any forward gear?), that is consistent with a torque converter issue. I'm curious if you ever feel a "bump" at the moment when, or within a second after, you stop at a light? There have been numerous reports of such behavior, and that seems to be related to torque converter function/ Dysfunction, where the transmission is NOT sufficiently and/or uniformly disengaged from the engine by the torque converter.

One test you might conduct is, with foot firmly on brake pedal, to lightly apply throttle so that idle speed per the tach is increased to 1,200 to 1,500 RPM, and see if the jerking is exacerbated, or diminished.

If all diagnostic testing I can devise suggests a transmission issue, since I have done most ALL my own auto diagnosis & repair, EXCEPT for AT, I would consult a specialist (Good local tranny shop). It is after all a GA6L45R GM transmission in 328xi.

Please let us know what you find & Merry Christmas!
George

I appreciate the thoughtful response!
I do get a little "bump" that I can feel physically.
I will try the brake and slight throttle tomorrow.
Also, I have the N51 warranty which will cover the torque converter (15 year warranty for N51 engines) however, wondering if BMW will repair it even if there is no check engine light that pop up

But thank you and happy holidays to you!

[CameroN7887]

I also have the n51 engine in my e92 328i and feel that bump when stopping when the cars cold, and as the car warms up it disappears. I was told it was from the transmission disconnecting from the engine due the the NIC (Neutral Idle Control) function of the car, and supposedly it can be coded out but your gas mileage will get coded out with it!
Following this thread just in case I'm gonna need to get a new torque converter, I'm at 100,800 currently!

[lowrydr310]

Originally Posted by CameroN7887

I also have the n51 engine in my e92 328i and feel that bump when stopping when the cars cold, and as the car warms up it disappears. I was told it was from the transmission disconnecting from the engine due the the NIC (Neutral Idle Control) function of the car, and supposedly it can be coded out but your gas mileage will get coded out with it!
Following this thread just in case I'm gonna need to get a new torque converter, I'm at 100,800 currently!

The bump from behind feeling is not always caused by Neutral Idle Control. It is more likely caused by faulty transmission solenoids or old fluid.

Try this: when stopped, put your car in Neutral and lightly hold the brake to just barely keep your car stopped, then shift into Drive. Let the car slowly creep forward then shift into Neutral. Do you feel that same harsh bump during these gear changes?

I had a very slight jolt when coming to a stop, when the transmission downshifted into 1st. This is commonly caused by bad solenoids. In my case, I did a drain and fill of the transmission fluid and the jolt has been eliminated.


As for the vibration, my car vibrates when stopped at a light in gear with my foot on the brake. It's a buzzy vibration though, and not nearly as severe like when my car had two cylinders misfiring. I still haven't checked my crankcase ventilation plumbing for leaks which could be the cause, however another cause could be worn engine mounts.

Have any E90 owners here successfully eliminated vibrations at idle by replacing the mounts?

[Fritzer]

When was the last time you or someone else cleaned the VANOS Solenoid? Relatively easy job.