[jacbo]

My N57 started having quite a rough idle but only on cold start. It is not very consistent and sometimes the revs only fluctuate a tiny bit, other times the roughness shakes the car quite a lot.

Once I start driving it is absolutely fine and doesn't have any issues. Even few minutes after setting off and stopping at traffic lights the idle is fine.

I don't have any fault codes at all and so far i have cleaned out the intake manifold and swirl flaps but that made no difference. (Yes i still have EGR so these get covered in carbon)

I did a smooth running check on ista (seems to check the correction fuel injection rate). Results during rough idle:

Cyl 1 -0.2
Cyl 5 2.6
Cyl 3 0.9
Cyl 6 -0.9
Cyl 2 -1.1
Cyl 4 -1.6

Ista tells me these are okay, accepted range is -5 to 4.

I also ran this test again when engine was hot and running smoothly and the results are:
Cyl 1 1.2
Cyl 5 -0.8
Cyl 3 1.2
Cyl 6 -0.3
Cyl 2 -0.7
Cyl 4 -0.9

All i can see from this is at rough idle cyl 5 injector seems to be a fair bit different compared to the others but still within spec.

Does anyone know more about this test and these values? I don't want to start throwing injectors in due to cost and effort before being certain that is the problem.

Or if someone has any suggestions let me know. Feel like i'm doing the engine no favours by leaving it as is

[lnxguy]

How are the glowplugs?

[jacbo]

Originally Posted by lnxguy

How are the glowplugs?

Replaced last year along with the controller

[392Hemi]

Relax, rough cold starts mean you have a cool car

[jacbo]

Update/fixed issue.

I remembered when i was replacing all the fuel injector copper seals, cylinder 5 was stuck and i never got round to replacing it. i got the proper slide hammer tool and changed it out. did the smooth running check and the values were now much closer across all 6 cylinders but rough idle was still present

I checked codes again and saw a swirl flap plausibility fault. I used ISTA to do a function check which opens and closes the swirl flaps. The value for actuation should be 95% but mine was reading around 75%. Took manifold off to find the plastic actuator arm was no longer connected to the swirl flap rod and was worn out and snapped around the hole (must have missed this when i had manifold off to clean it!).

Ordered a delete kit (don't worry i didn't use the awful manifold seals provided). Ripped the swirl flaps out which was very easy tbf. Also found the rubber seal between the rod and swirl flap actuator turned solid so had a boost leak from there. Started engine up, no more rough idle and did the ISTA test on swirl flaps which was reading 95% now (obviously the actuator is not connected to anything now but as long as the ECU thinks it's doing it's job it's all good)

Conclusion, check your swirl flap system if you have rough idle. Car is on 160k miles now so not surprising these plastic parts have started to degrade and wear out.

Driving feel is a little different without swirl flaps but the power delivery is much smoother past 2k rpm and no more car shaking like a shittin dog on idle

[392Hemi]

Originally Posted by jacbo

Update/fixed issue.

I remembered when i was replacing all the fuel injector copper seals, cylinder 5 was stuck and i never got round to replacing it. i got the proper slide hammer tool and changed it out. did the smooth running check and the values were now much closer across all 6 cylinders but rough idle was still present

I checked codes again and saw a swirl flap plausibility fault. I used ISTA to do a function check which opens and closes the swirl flaps. The value for actuation should be 95% but mine was reading around 75%. Took manifold off to find the plastic actuator arm was no longer connected to the swirl flap rod and was worn out and snapped around the hole (must have missed this when i had manifold off to clean it!).

Ordered a delete kit (don't worry i didn't use the awful manifold seals provided). Ripped the swirl flaps out which was very easy tbf. Also found the rubber seal between the rod and swirl flap actuator turned solid so had a boost leak from there. Started engine up, no more rough idle and did the ISTA test on swirl flaps which was reading 95% now (obviously the actuator is not connected to anything now but as long as the ECU thinks it's doing it's job it's all good)

Conclusion, check your swirl flap system if you have rough idle. Car is on 160k miles now so not surprising these plastic parts have started to degrade and wear out.

Driving feel is a little different without swirl flaps but the power delivery is much smoother past 2k rpm and no more car shaking like a shittin dog on idle

Just did my delete at 153k, Surprised these swirl flaps even got approved to go into an intake. Cheesey stuff.

[BMWmadness994]

I have the same issue with the same sort of readings. I checked actuator arm and swirll flaps. However in ista my close position goes a faar as 91%. Same rough running on cold starts for 5minutes

[jacbo]

from what i remember the ECU is looking for a strict 95% value so i feel yours might just not be operating fully. maybe too much carbon build up? have you removed intake manifold and cleaned out the carbon?

[BMWmadness994]

Yeah i did take off the manifold and clean the swirl flaps. Moved them open and closed and they seem to be functioning as they should. But i didn’t do this with ista, plus i’m not receiving any codes which makes me believe maybe it’s ok.

Now i’m thinking maybe i should take the actuator off from the front of the manifold and test it via ista to see if it goes to 95% without any resistance.

Do you know at 95% if thats the value closed or open?

[jacbo]

That's a good idea actually then you can deduct where the issue is.

If I remember correctly it was for opening the flaps but honestly i'm not 100% certain.

Also have you tried doing the "smooth running test" on ista? i think this checks the fuel rate in each cylinder but that might give you some clues

[BMWmadness994]

So these are my values at cold start idle

Cylinder 1: -0.1 | 0.6
Cylinder 5: -0.9 | 0.0
Cylinder 3: 0.0 | 0.7
Cylinder 6: -0.8 | 0.0
Cylinder 2: 0.0 | 2.5
Cylinder 4: -1.1 | 0.0

Changed Injector on Cylinder 2 - Same results.

I’ve seen cylinder 2 as high as 4.0+ which triggers the smooth running controler fault.
This is when i managed to bump into your post, now i’m leaning towards. Maybe i didn’t clean the intake throughly and its to do with the swirl flaps

I would do the ista setup test but it requires me to go through other procedures that require the engine started.

I’ll try take the intake off again tomorrow, i have a delete kit so might just take out the swirl flaps anyway

[jacbo]

fair enough i see, good luck. can always put the swirl flaps back in i guess

[BMWmadness994]

Just an update from me

So deflapped the car and cleaned the intake manifold out spotless. Put everything back together, car drove fine for 1 week then started misbehaving again. Assume it is because it relearns the fuel trims

So i tried the following, moved injector 2 to 4 check smooth running control, same behavour on cylinder 2. Then also have a spare injector as i swaped this one out a while ago, replaced that with cylinder 5 (yesterday). Coded injector and did injector adaptions

Running out of ideas now, so close to selling the car or drive it into a wall!!

So faar
Dpf has been deleted, this issue was there before the remap so it’s definitely not that.
Egr has been deleted and unpluged, check the value and that’s definitely closed
Swirl flaps have been removed

Not sure what it could be, either i have a leak somewhere. But would of thought it would trigger a fault in ecu or performance would decrease non of that is happening

Or i have a faulty injector on cyl 1,3,6 as these haven’t been touched or moved yet

I’ve attached a screenshot of the rough running parameters at cold from two days ago

My next move is smoke test for leaks
Or
Leak down test on injectors

Not sure which one to do first