[PaulForeman]

Hi all - I need some help. Have done a lot of searching on here, YouTube, etc, and have yet to find anyone reporting this problem.

Car is a 2011 335i, xdrive, N55, with a 6 speed manual, ~78k miles, in Tasman Metallic; not that that has anything to do with it, but Tom and Ray would always ask.

No service engine light, oil changed 5K miles ago with recommended BMW LL01 equivalent, running 91 octane, and all stock except for VRSF turbo outlet and charge pipes (OEM were cracked).

This just started a week ago. Occasionally when I'm at a stop, the throttle "sticks open" when I push the accelerator pedal down and then let go. It stays at the rpm I revved it to, and then slowly creeps higher and higher. YouTube link here:

https://youtu.be/Ekp9A_Y1uWo

I have tried putting it in gear and letting clutch out a little bit to see if that fixes it. It does not. The engine speed/RPMs drop a little bit, but as soon as you press the clutch, it starts gaining RPMs again. You can see it in the video. The only thing that gets it to stop is turning off the car. It has happened a few times when shifting at slower speeds (usually between 1/2 and 2/3 shifts) as well. I assume it's related, but sometimes while shifting (at any speed), the RPMs are very slow to drop to the correct RPM for the next gear. Like 7 seconds to drop 1500 RPMs...

Has anyone ever experience this in the auto or manual?

-Paul, a relatively novice BMW owner.

[HondaRC51]

Id pull the throttle body off and see if the blade has free movement or if anything might have been sucked up inside that would cause the throttle blade to get caught. Shouldn't take but 30 minutes to pull off.

[PaulForeman]

Originally Posted by HondaRC51

Id pull the throttle body off and see if the blade has free movement or if anything might have been sucked up inside that would cause the throttle blade to get caught. Shouldn't take but 30 minutes to pull off.

Good advice; I will check again, but I have done this recently, as I replaced the cracked OEM charge pipe a handful of months ago. At the time, I checked out the throttle body then and it seemed to be fine. No buildup of oil or carbon. No rattling, etc. But I may need to check it again.

EDIT: I DON'T THINK THE MAP HAS ANYTHING TO DO WITH IT. Updated the below paragraph with findings.

I thought I may have discovered a possibly related issue - I thought my MAP sensor reading may not be correctly anymore. Have a friend with another 2011 335xi N55 and the MAP reads like 11.7psi at idle on his car. Mine reads like ~4psi. Not sure why there's a discrepancy.

I ordered a new MAP sensor and replace that to see if that fixes the issue. No dice. The pressure still reads the same at idle (~4psi) but still reads about 22psi at WOT.

[JinAM]

Hi Paul, did it fix your issue?

[PaulForeman]

Originally Posted by JinAM

Hi Paul, did it fix your issue?

No. The new MAP sensor still reads low (4-5psi) at idle and the throttle still sticks occasionally. Interestingly, I read the MAP sensor off a friends Honda Odyssey and it also read about 4-5psi at idle, so I'm kinda abandoning that through train for now. I actually wonder if my other buddy with the 2011 N55 E90 has a cracked charge pipe or something.

Can anyone confirm what your N54 or N55 reads at the MAP sensor using and OBDII scanner?

On the throttle sticking issue... I went to the dealer and asked them about the "sticking" throttle/valvetronic. They recommended I change the oil and then bring it in to have them read the BMW-specific codes. I have not done this yet so I do not know if the BMW computer is reporting any of the valvetronic issues. I'm going to change the oil tomorrow with 5W-30 BMW LL-01 and use a MANN/BMW OEM filter. I'll see if that helps, but I'm suspicious that the valvetronic motor gear and/or the lifter cam gear are worn out... if so, the damage has already been done and changing the oil probably won't make much difference. TBD!

I may try some oil additives from Liquimoly, but not sure if it's worth it or not. Don't want to add things to the N55 there any chance it will do additional damage.

Sorry for being so wordy - I'm kinda keeping this thread for my own records too to keep track of what I've done to try to fix this problem.

[PaulForeman]

Car is throwing valvetronic codes. I think the valvetronic motor is weak and not responding correctly to throttle input and that's what's getting stuck.

Turns out, it I start the car and let it sit idling for about 15-20 seconds, the revs bounce around for a few seconds, then settle down and the throttle will not "stick" for that entire drive. But if I start the car and drive immediately, the throttle will occasionally stick during that drive. Idling the car temporarily to avoid throttle sticking issues works 100% of the time as far as I can tell.

Working theory - the valvetronic is the primary throttle mechanism. When the car starts up, it goes through some checks and then the car goes "nope, bad valvetronic motor." The car then opens the valvetronic and transitions to using the throttle body for air intake control. I guess if I immediately start driving, I interrupt that valvetronic test process and the car stays in valvetronic mode? I've been told that normally, the throttle body is wide open when the valvetronic is working correctly, so it makes sense to me that once the revs settle down, that's a sign of the valvetronic opening and throttle body becoming the primary throttle.

[PaulForeman]

Followup - had this car into the dealer and they quoted me $4400 to replace the entire valvetonic system (motor, eccentric shaft, needle bearings, etc).

Took it to a 3rd party specialty shop for a 2nd opinion. They charged me $140 for about 1.5 hrs of labor. Ran a valvetonic diagnostic and calibration test and the car passed every gate in the test. Shop was then not able to replicate the problem.

Ever since then, the car runs 100% perfectly. Seems like the valvetonic somehow got out of calibration or something. The independent shop fixed it. Happy to have saved the $4400. Probably taking it to this shop for anything else in the future!

[PhaceN52]

Originally Posted by PaulForeman

Followup - had this car into the dealer and they quoted me $4400 to replace the entire valvetonic system (motor, eccentric shaft, needle bearings, etc).

Took it to a 3rd party specialty shop for a 2nd opinion. They charged me $140 for about 1.5 hrs of labor. Ran a valvetonic diagnostic and calibration test and the car passed every gate in the test. Shop was then not able to replicate the problem.

Ever since then, the car runs 100% perfectly. Seems like the valvetonic somehow got out of calibration or something. The independent shop fixed it. Happy to have saved the $4400. Probably taking it to this shop for anything else in the future!

They don't miss a chance to confirm that stealership is the most accurate way to refer to 'em
Good you sorted it out

[PaulForeman]

Originally Posted by PhaceN52

They don't miss a chance to confirm that stealership is the most accurate way to refer to 'em
Good you sorted it out

Yeah... Bummed they didn't even mention trying a calibration on it. But not surprised. Will definitely return to this shop in the future!