Rough Idle?

msk340i · 10-21-2019, 06:45 PM

It's not REALLY rough idle but the RPMs dip for one second after strating the car (doesn't matter if it's warm or cold) then idles perfectly smooth. The car has high flow downpipe and stage 2 BM3. Any ideas?
It can be seen at second 6 in this video.
https://photos.app.goo.gl/GLkCWVfHH19FJqcw6

BPAC306 · 10-21-2019, 07:00 PM

Quote:

Originally Posted by msk340i

It's not REALLY rough idle but the RPMs dip for one second after strating the car (doesn't matter if it's warm or cold) then idles perfectly smooth. The car has high flow downpipe and stage 2 BM3. Any ideas?
It can be seen at second 6 in this video.
https://photos.app.goo.gl/GLkCWVfHH19FJqcw6

I have Bm3 stage one and experience this also. I strongly believe it has something to do with selecting the cold start OFF function. My idle smells a bit more rich than stock.

msk340i · 10-21-2019, 07:03 PM

Quote:

Originally Posted by BPAC306

I have Bm3 stage one and experience this also. I strongly believe it has something to do with selecting the cold start OFF function. My idle smells a bit more rich than stock.

If I enable cold start then I don't know what will happen? Will the catalytic warming "mask" the issue or make it disappear? I think I should revert to stock and see how it goes.

msk340i · 10-22-2019, 11:24 AM

Anyone has other ideas?

Ahanix · 10-22-2019, 12:48 PM

Quote:

Originally Posted by msk340i

Anyone has other ideas?

What are your plugs gapped to right now?

msk340i · 10-22-2019, 01:35 PM

Quote:

Originally Posted by Ahanix

What are your plugs gapped to right now?

They are the stock plugs that BMW installed when the made the car.

AddictedTo///M · 10-22-2019, 07:22 PM

My 340i does the same thing....

msk340i · 10-22-2019, 08:25 PM

Quote:

Originally Posted by AddictedTo///M

My 340i does the same thing....

And it's accepted to be normal?

AddictedTo///M · 10-23-2019, 07:23 AM

Quote:

Originally Posted by msk340i

And it's accepted to be normal?

I don't think so.

I have stock gap on my plugs, so I just assumed it was because of this. I'm going back to stock next week, we will see what happens.

340iNL · 10-23-2019, 10:06 AM

Quote:

Originally Posted by AddictedTo///M

I don't think so.

I have stock gap on my plugs, so I just assumed it was because of this. I'm going back to stock next week, we will see what happens.

I also have stock gap but after 5.000 km on stage 1 my car is rough on idle when warm and cold.

After 1.000 km stock tune the rough idle seems to get less rough.

The dme can't really handle all those big changes I guess.

My car also detects knock but did this before I installed bootmod3.

Maybe i'm going to try the stage 1 low octane map, maybe this will be handeled better with stock gaped plugs...

10-21-2019, 06:45 PM	#1
msk340i Major 1320 Rep 1,134 Posts Drives: 340i M sport Join Date: Jan 2019 Location: Orlando, FL iTrader: (1)	Rough Idle? It's not REALLY rough idle but the RPMs dip for one second after strating the car (doesn't matter if it's warm or cold) then idles perfectly smooth. The car has high flow downpipe and stage 2 BM3. Any ideas? It can be seen at second 6 in this video. https://photos.app.goo.gl/GLkCWVfHH19FJqcw6
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10-22-2019, 11:24 AM	#4
msk340i Major 1320 Rep 1,134 Posts Drives: 340i M sport Join Date: Jan 2019 Location: Orlando, FL iTrader: (1)	Anyone has other ideas?
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10-22-2019, 07:22 PM	#7
AddictedTo///M Second Lieutenant 217 Rep 228 Posts Drives: 2022 BMW M340i xDrive Join Date: Apr 2016 Location: O-H iTrader: (1)	My 340i does the same thing....
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