135i N55 6MT, hanging or holding revs?

[Rub10s]

Hey everyone, purchased a 2012 135i as the 2nd owner about 8 months ago. Car has been great, I have a BMW clutch stop, BMS intake, and stage 2 JB4.

I've noticed ever since I got the car that sometimes the revs will hang when I go to shift. Let's say I'm rolling up to a stop sign in first, at about 2500 rpm. When I go to clutch in to roll to the stop sign, the revs will sit at around 2200 and just hold until I put it in neutral.

It did this well before the JB4 or anything else.

I originally thought this must be some rev match thing, but it just occurred to me after helping a friend with a vacuum leak that mine could be a leak as well.

Unfortunately I can't replicate it on demand, or I would just take it to the dealer.... but I also don't want to seem like a dumbass if this is a "feature".

I did some searches but nothing popped out, but if I missed something feel free to yell at me

Thanks!

[alexc93]

I get it too sometimes, but rarely...

not sure why it does it. I never went to the dealer because its didn't really affect the drivability of the car..

curious too though

[blutattoo]

Originally Posted by Sheldon

Hey everyone, purchased a 2012 135i as the 2nd owner about 8 months ago. Car has been great, I have a BMW clutch stop, BMS intake, and stage 2 JB4.

I've noticed ever since I got the car that sometimes the revs will hang when I go to shift. Let's say I'm rolling up to a stop sign in first, at about 2500 rpm. When I go to clutch in to roll to the stop sign, the revs will sit at around 2200 and just hold until I put it in neutral.

It did this well before the JB4 or anything else.

I originally thought this must be some rev match thing, but it just occurred to me after helping a friend with a vacuum leak that mine could be a leak as well.

Unfortunately I can't replicate it on demand, or I would just take it to the dealer.... but I also don't want to seem like a dumbass if this is a "feature".

I did some searches but nothing popped out, but if I missed something feel free to yell at me

Thanks!

Yep same thing here. When the throttle hangs I tap the throttle, rev it a little and that fixes it. I haven't figured out the cause and it seems intermittent. I have a 2012, but no JB4 so it's not that for sure.

[cdde323]

If you let the clutch back out... does the car pull like you're giving it gas? Does applying the brake with the clutch in do anything to the RPM's or does this happen only when free rolling with the clutch in?

I have an N54, I haven't experienced this problem... but your problem almost sounds like a short in the digital throttle... might want to pop the pedal off and see if there is corrosion or the connector is loose.

I've also read that if cruise control is on, the car will maintain RPM's when you clutch in because it's preparing for you to switch gears... but it times out and if the clutch is in for an extended period, the RPM's drop... so maybe you're seeing this cruise control delay? I'm just guessing.

[Freon]

Intakes on cars with MAF-based fueling can screw up the readings and cause things like this.

You can try putting the stock intake back on and make sure there are no leaks in the intake system.

[siegester]

Originally Posted by Freon

Intakes on cars with MAF-based fueling can screw up the readings and cause things like this.

You can try putting the stock intake back on and make sure there are no leaks in the intake system.

I know the N54 uses a MAP, doesn't the N55 too?

[tuj]

I know the N54 uses a MAP, doesn't the N55 too?

No, N55 is MAF.

[Muredhawk]

Mine does this too and started shortly after I put my BMS intake on.

Although it hasnt really bothered me.

[Curare86]

Hmm mine does too. Also have intake. Just been ignoring it for a long while and car runs fine. It always hangs just over 2000rpm too, never anywhere else in rev range.

[Freon]

Originally Posted by cdde323

. but your problem almost sounds like a short in the digital throttle... might want to pop the pedal off and see if there is corrosion or the connector is loose.

I'm very doubtful. The DBW throttle systems have a number of failsafes. Typically several position sensors that all have to be equal or the whole system shits a brick and won't let you drive.

[cdde323]

Originally Posted by Freon

I'm very doubtful. The DBW throttle systems have a number of failsafes. Typically several position sensors that all have to be equal or the whole system shits a brick and won't let you drive.

Fair enough... I don't really know much about the throttle system and where/how it can fail, just a habit of checking for bad connections when problems are intermittent. It has saved me some headaches every once in awhile.

If you google "N55 rev hang", there is a number of posts from other forums. Blame is usually aimed at the heavy flywheel or that it's programmed into the DBW system for emissions reasons.

[tuj]

Most DBW throttles use two potentiometers and the ECU compares the value between the two. If its not within a certain tolerance, the signal is disregarded and the system goes into fail-safe.

[Dackelone]

I would check for shadow codes thrown. You could have a code but not an ECL on. Since you have a N55 there is no traditional throttle body, its all done via the DME changing cam timing. ala Valvetronic. So you could have a bad vanous(there are two!) or maybe the wrong type of engine oil(too thick or type) and or something else. First thing is to check for codes.

Dack

[Rub10s]

Does the JB4 check for "shadow codes"? If so I'll plug in on the way home.

[Bonafide]

I have the same problem, have a 2012 135i 6speed manual.

this is what happens in these steps:
-driving
-rev over 2500
-clutch in, let go of gas
-rev drops (as it should) rev stops and hangs at 2200-2300 for about 2 seconds
- rev drops to idle
-engage gas and release clutch to bring rpms back up to driving range

essentially this happens from 1st to 3rd gear

not sure what is up.. I have stage 2 dinan but the other cars that do this too don't have mods or have a jb4..

[MightyMouseTech]

Originally Posted by cdde323

I have an N54, I haven't experienced this problem... but your problem almost sounds like a short in the digital throttle... might want to pop the pedal off and see if there is corrosion or the connector is loose.
.

I doubt that is it. Because it is a safety system, there are actually two sensors in there. If they don't match precisely, you will get a code. Very unlikely they are both off the exact same amount due to corrosion.

[Rub10s]

Originally Posted by Sheldon

Does the JB4 check for "shadow codes"? If so I'll plug in on the way home.

Was logging today for a different issue and I finally checked codes via the JB4. Nothing.

[CGMike]

My evo did the same thing but way worse than my N55, it drove me crazy. I only notice it on the BMW between 1st and 2nd gear. Its like the RPMs stay high as Im shifting, when I let the clutch out, the car lurches forward in 2nd gear. Stupid drive by wire. My GTO and WRX (DBW) do not do any of these things.

[Orpo]

I'm rezzing this thread from the dead because I have this issue too.

New to me, 2012 135i M-Sport
45,000 KM
6 Speed MT
BMS Intake
No other mods

Throttle will hang around 1900-2500 RPM from 1-3 gears. IMO it is very dangerous as the car will lurch forward unexpectedly when engaging the next gear. It can be scary in traffic.

Has anyone found the root of this problem? Seems like it might be linked to the aftermarket intake? I have not taken the BMS Intake off yet, but that is my next step.

Thanks

[MightyMouseTech]

Interesting, my 2013 has never done anything like this.

Can't be the throttle body, as well, the N55 does not have one.

Maybe the Valvetronic system is getting sticky. How often is the oil changed on the car, running a heavier/thicker oil than recommended?

[Orpo]

Originally Posted by MightyMouseTech

Interesting, my 2013 has never done anything like this.

Can't be the throttle body, as well, the N55 does not have one.

Maybe the Valvetronic system is getting sticky. How often is the oil changed on the car, running a heavier/thicker oil than recommended?

Do you have a BMS Intake on your 2013?
Oil was changed recently with Mobile 1 0w-40 european car synthetic.

[MightyMouseTech]

Originally Posted by Orpo

Do you have a BMS Intake on your 2013?
Oil was changed recently with Mobile 1 0w-40 european car synthetic.

Sorry, no I don't.