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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Wed, Apr-04-2018, 12:56:10 PM   #21
tjkenny15
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Default Re: Absolutely stumped. Very rough Idle.

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Originally Posted by ThunderMoose View Post
Your pre cat O2 sensors are swapped. Go under neath the car and swap them at the bungs.


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Agreed. Are you running a tune?
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Old Wed, Apr-04-2018, 04:54:13 PM   #22
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Default Re: Absolutely stumped. Very rough Idle.

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Agreed. Are you running a tune?
Outside of tuning out the cats and SAP, not yet. Didn't want to introduce a new map until I have this issue figured out.
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Old Sun, Apr-08-2018, 04:36:53 AM   #23
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Default Re: Absolutely stumped. Very rough Idle.

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These codes do imply your precat O2's are the wrong way around.

What's happening in that case is bank 1 will measure lean and bank 2 will measure rich. DME tries to counteract but this is simply worsening the issue.

You can tell this if your code/OBD2 tool can read live data, the O2 sensors need to move beteen 0.1V and 0.9V all the time. If they are swapped bank one will be at 0.1V all the time and bank 2 will be at 0.9V all the time.

These sockets that sit under the engine cover plate can easily be swapped around. You can't tell this without reading data or tracing the wires back to the DME.

I doubt you have injector issues and both cylinder banks will start to counteract eachother.
Bert,

I was really hoping this was the issue. I checked both pre cat from the top, and got underneath the car and removed the skid plate, and checked the posts as well, and everything is where it is supposed to be. I'm just at a loss at this point. Would there be any other reason that those codes could be thrown, and showing that weirdness from reading the O2 sensor voltage?
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Old Sun, Apr-08-2018, 05:08:47 AM   #24
Bert ///M3
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Default Re: Absolutely stumped. Very rough Idle.

Did you trace them back to the DME as well?

I would have swapped them and given it a try anyway if you had all the stuff off.

Because it's easy to swap the position of the sockets underneath the cylinder cover and then it appears that you have them in the right place.

I wouldn't know any other reason why it would throw these specific codes.

Or actually, easy way to check is disconnect one. You can see on the fault codes or the datastream if they are right. Disconnect bank number 2 underneath the engine cover and see if bank 2 shows up in the fault codes, or if the datastream returns 0.45V for bank 2. That will tell you if they are in the right place for sure.
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Old Sun, Apr-08-2018, 01:45:53 PM   #25
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Default Re: Absolutely stumped. Very rough Idle.

I still I am not sure how you can tell if they are correct. There is absolutely no marking on the top to tell you which is which. The electrical connectors have different connectors but there is conflicting information on the web as to which is which. So it is next to impossible to just trace it back.

Why not swap at the bungs and see what happens?
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Old Sun, Apr-08-2018, 04:07:15 PM   #26
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Default Re: Absolutely stumped. Very rough Idle.

How rough are we talking? Can you post a video?
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Old Sun, Apr-08-2018, 10:12:31 PM   #27
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Default Re: Absolutely stumped. Very rough Idle.

I had this same problem on a customers car who recently had all four of his oxygen sensors replaced. Viewing live data you would see bank 1's upstream sensor voltage climb almost to 1 volt where bank 2 upstream would stay at 0v and the car would run like it was misfiring. After about 30 seconds Bank 1 voltage would slowly drop to 0 and then Bank 2 would slowly climb to almost 1 volt and then again run like shit. When both O2 sensors were at 0 volts, the car would run smooth for that short time.
I ended up disconnecting all four oxygen sensors and MAF and the car ran smooth.
Finally realized just clearing the codes wasnt enough. You need to reset the adaptations. Specifically your fuel trims.
Not saying this will solve your issue, just something to try.
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Old Mon, Apr-09-2018, 03:16:13 AM   #28
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Default Re: Absolutely stumped. Very rough Idle.

What he said. Reset DME adaptations. Good Luck

Quote:
Originally Posted by CSLM3Wannabi View Post
I had this same problem on a customers car who recently had all four of his oxygen sensors replaced. Viewing live data you would see bank 1's upstream sensor voltage climb almost to 1 volt where bank 2 upstream would stay at 0v and the car would run like it was misfiring. After about 30 seconds Bank 1 voltage would slowly drop to 0 and then Bank 2 would slowly climb to almost 1 volt and then again run like shit. When both O2 sensors were at 0 volts, the car would run smooth for that short time.
I ended up disconnecting all four oxygen sensors and MAF and the car ran smooth.
Finally realized just clearing the codes wasnt enough. You need to reset the adaptations. Specifically your fuel trims.
Not saying this will solve your issue, just something to try.
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Old Tue, Apr-10-2018, 02:37:49 PM   #29
tomandhisjones
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Default Re: Absolutely stumped. Very rough Idle.

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Originally Posted by SE46 View Post
What he said. Reset DME adaptations. Good Luck
Done that a few times, with INPA and a BMW specific scanner I purchased from Amazon. Still not working. Car has just died a few times over the last couple of days out of nowhere, when putting the clutch in rolling up to a light.
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Old Tue, Apr-10-2018, 03:11:23 PM   #30
xM P0W3Rx
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Default Re: Absolutely stumped. Very rough Idle.

Definitely sounds like swapped O2's. I dealt with this nightmare before and it literally got to the point where I removed all 4 O2's and reinstalled each individual one in there prospective places. It's incredibly easy to mess up.
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Discussing Absolutely stumped. Very rough Idle. in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)