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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 Tue, Nov-14-2017, 08:04:07 PM   #1
gregdepot
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Default Misfires on 4-6 after header install

I don't think pre O2s are crossed sinced they not seem long enough and only one miss fire code at 7400 rpm on cylinder 2. (206)


Maybe the bank 2 pre sensor was damaged? At 840 and 1640 rpm missfires on 4-6 cylinders



Any suggestions?


Uploading an image failed and I don't think photo bucket works anymore
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Old Tue, Nov-14-2017, 09:54:25 PM   #2
erickrayos
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Default Re: Misfires on 4-6 after header install

from what I understand, pre sensor doesn't have anything to do with your fuel/air mixture. its just there so that it can see if there's any difference in readings between the pre and post cat sensors and based on the post cat sensor readings that's where the computer adjust the fuel/air ratio.. but then again I don't think it would cause you to get misfires...

try putting the coils from that cylinder to another and see if the misfire moves to that. and or spark plugs.
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Old Tue, Nov-14-2017, 10:07:13 PM   #3
95bullet
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Default Re: Misfires on 4-6 after header install

The pre cat bank 1 and bank 2 sensors are excatly the same length. You likely have them switched.

The pre cats adjust mixture post cats and egt verify the cat functionality
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Last edited by 95bullet; Tue, Nov-14-2017 at 10:24:20 PM.
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Old Tue, Nov-14-2017, 11:19:42 PM   #4
gregdepot
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Default Re: Misfires on 4-6 after header install

It looks like the sensors were installed differently at the factory then diagrams and wire looms were backwards the car is now working
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Discussing Misfires on 4-6 after header install 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)