[RuskiE39]

Hey All,

Having my first real issue with our 2015 N55 335i Auto. Car has no mods or tunes and about 80K miles.

The car belongs to my wife so i'm not privy to how often this happens, but i've been doing some garage work over the past few weeks and have been moving the cars in and out and noticed that on cold starts it turns over and surges for 2-3 seconds and then smoothes out.

Two times now it has turned over, surged for 2 seconds and then just shut off. Yesterday it did this twice and on the third try it turned over no problem.

The car is in exceptional condition with no codes, regularly has it's oil changed and inspected at the dealership. I changed the spark plugs (2) weeks ago and replaced the air filter while in there. (This issue was present before changing the spark plugs).

I have a VRSF charge pipe on the workbench i've been meaning to get around to installing which has me wondering if this is potentially a cracked charge pipe or vacuum leak somewhere? Maybe a dirty MAF?

Any ideas where to start?

Found this video below which shows almost exactly what ours is doing:
https://youtube.com/shorts/i3aKNQFVNTE?feature=share

TIA

[Billfitz]

No codes? Hard to believe.

[RuskiE39]

Originally Posted by Billfitz

No codes? Hard to believe.

No Check Engine light, anyways. Unless there's a ghost code?

Just checked with my dongle, no confirmed or pending codes...

[Billfitz]

If I fart in the car it will toss a code, let alone anything serious enough to cause a shut down. Perhaps your code reader isn't up to the task.

[oem.plus_440gc]

My wife's X5 (F15 N55) does the same thing occasionally. I initially thought it was a batch of bad gas that had some residual shit in it (she got gas from a gas station that had been closed for a few months under construction, figured bad gas/water had been in the tanks). That was over a year ago. It still does it occasionally, but most of the times it starts, surges for a second or 2 and then is fine. Very rarely (a handful of times in the past year) it will bog down and stall on the first try, but then will fire right up and be fine on the second try.

Seems to happen more often in warmer weather with cold starts. I think it has something to do with the AC being on when the car starts and its almost too much strain during the initial cold start to try to get the AC working while starting the car and running all the other accessories.

EDIT: No codes at all, had the battery tested.

[Billfitz]

The AC should have no bearing on it. The power management system prioritizes the starter function over all else. If it detects a low voltage situation it will shut off other devices. You see that when using auto start-stop. If the battery voltage is low it will shut down the radio and other items while re-starting, turning them back on afterwards.

[RuskiE39]

Yeah that is odd that this issue started up with the warmer weather.

I don't think it's a battery issue, i've bled my coolant a few times in the past month using the electric water pump method and haven't seen any indication of a weak or failing battery. I'll keep an eye on it but let the wife know to not be too worried unless it throws codes.

[_das_bae_]

Originally Posted by RuskiE39

Hey All,

Having my first real issue with our 2015 N55 335i Auto. Car has no mods or tunes and about 80K miles.

The car belongs to my wife so i'm not privy to how often this happens, but i've been doing some garage work over the past few weeks and have been moving the cars in and out and noticed that on cold starts it turns over and surges for 2-3 seconds and then smoothes out.

Two times now it has turned over, surged for 2 seconds and then just shut off. Yesterday it did this twice and on the third try it turned over no problem.

The car is in exceptional condition with no codes, regularly has it's oil changed and inspected at the dealership. I changed the spark plugs (2) weeks ago and replaced the air filter while in there. (This issue was present before changing the spark plugs).

I have a VRSF charge pipe on the workbench i've been meaning to get around to installing which has me wondering if this is potentially a cracked charge pipe or vacuum leak somewhere? Maybe a dirty MAF?

Any ideas where to start?

Found this video below which shows almost exactly what ours is doing:
https://youtube.com/shorts/i3aKNQFVNTE?feature=share

TIA

My guess is fuel pump if you’ve already checked for vacuum leaks. Given the car was starting fine before and battery is fine sounds like spark is less likely the culprit. My fuel pump went at about 70k last year due to the shop not tightening the intake clamps. The car surging is usually the ecu trying to adapt to air and fuel ratio as well as warm up the fluids etc during start up. If it’s cutting out the car is probably running lean meaning fuel supply is obstructed or too much air is flooding the throttle body that the car essentially chokes and stalls out. Fuel pumps won’t throw a code till it’s too late, especially if it’s on the way out.

Maybe try asking the wife if the car has had inconsistent throttle recently or rpm’s stumbling while stopped in park or drive. That will be a tale tell sign it’s fuel related. From there it’s the pump or injectors. It’s rare for n55 around that age to have injectors go. Hope this helps, good luck!

[thejeremyman9]

Low fuel pressure would definitely throw a code. If you think its the MAF, start the car with the MAF unplugged and see if the problem still occurs. Vacuum leak will sometimes but not always throw a code right away. I would inspect the CP though if its stock, if you dont smoke test.

[_das_bae_]

Originally Posted by thejeremyman9

Low fuel pressure would definitely throw a code. If you think its the MAF, start the car with the MAF unplugged and see if the problem still occurs. Vacuum leak will sometimes but not always throw a code right away. I would inspect the CP though if its stock, if you dont smoke test.

+1 Good advice to check the CP. A lean or rich condition caused by a vacuum leak should show up as a soft code at the minimum.

Although it is not necessarily true about the lpfp throwing a code. In my experience, my intake was not attached (popped loose at the base under heavy boost) and the car was able to drive 110 miles with no code/drivetrain error (it however appeared as a soft code/intermittent error). The car adapted to the extra air and was just very sluggish, but once I reached home the lpfp was struggling and the car sounded like a cammed V8 on the next start-up. If you have a full tank, the hpfp can be pulling enough vacuum/fuel to compensate for a weak pump -- this is harder to detect in eco mode vs sport where the rpms have a higher target.

[thejeremyman9]

Originally Posted by _das_bae_

+1 Good advice to check the CP. A lean or rich condition caused by a vacuum leak should show up as a soft code at the minimum.

Although it is not necessarily true about the lpfp throwing a code. In my experience, my intake was not attached (popped loose at the base under heavy boost) and the car was able to drive 110 miles with no code/drivetrain error (it however appeared as a soft code/intermittent error). The car adapted to the extra air and was just very sluggish, but once I reached home the lpfp was struggling and the car sounded like a cammed V8 on the next start-up. If you have a full tank, the hpfp can be pulling enough vacuum/fuel to compensate for a weak pump -- this is harder to detect in eco mode vs sport where the rpms have a higher target.

Just to clarify, when i say code, I mean actually scanning for codes, including shadow/historical codes. Not a CEL, which has a much higher threshold than triggering a shadow or an active code stored in the DME (which can be done with no CEL).

[RuskiE39]

Just a quick update; I recently upgraded my charge pipe and noticed oil on the MAF sensor.. cleaned it up and cars been starting up smooth ever since. Will update if that changes.

[bloodline129]

I’ve had the same issue for years now. It hasn’t stalled yet like yours but upon cold starts the car “sometimes” bogs down to almost stalling and then it surges up like crazy and levels out.

Roll back 2 years ago I only drove 6/8km to work and back and thought it’s related to that, because after I moved and my daily commute increased to 120km it somewhat disappeared.

Recently it’s back at it and I just done a 2000km trip and put a can of liquid moly injection cleaner in it as well.

No shadow codes stored that I could find on my foxwel 530 or BimmerLink pertaining to it.

[Billfitz]

Originally Posted by RuskiE39

Just a quick update; I recently upgraded my charge pipe and noticed oil on the MAF sensor.. cleaned it up and cars been starting up smooth ever since.

Yearly cleaning of the MAF and MAP sensors is a must.