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Discussion Starter · #1 ·
I started to have an issue with bogging around 2500 RPM after installing eBay headers. I keep hearing about swapping O2 sensors by mistake and was wondering about that? However, I have no post-cat sensors in (unplugged). I did have to use a 90 degree adapter on a pre-cat sensor and im wondering if that pulled the sensor out of the flow enough to cause the car to bog occasionally due to lack of sensing and adjustments in AFR.
 

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I would say that a pre-cat O2 should not be pulled out of the flow stream to read properly. Post cat O2's, that works fine but the upstream needs to see all the AFR changes ASAP and accurately.

I am about to do this as well and am wondering if you have any pics of which O2 bung needed the modification? Also which brand of headers did you use? My set I purchased for my 04 330Ci 6 speed is a Chinese mfg. # HD-BE4602
 

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While the Pre-cat O2 sensors are pulled out of the exhaust stream is not ideal, they may still work, but not very well.

Not sure this is the cause of the bogging.

My guess is this is either a fuel starvation issue and/or a DME ignition timing problem.

Read toward the end of this thread and see how OBDFusion can be your friend as well as how basic maintenance is required to keep these cars running correctly: http://forum.e46fanatics.com/showthread.php?t=1223620

As far as the DME Ignition Timing Map problems, read these threads:

http://forum.e46fanatics.com/showthread.php?t=966614

http://forum.e46fanatics.com/showthread.php?t=1121703
 

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The precast o2's should should definitely not be pulled out of the stream and if only 1 sensor is out of stream the sensors are going to read vastly different especially considering you are using a 90 degree over a straight regular. Both precat sensors should be reading pretty close to each other at all times. This can be verified with a scan tool. Also when I did my header my car though a code for oxygen sensors swapped. I do have a sulev vehicle so maybe standard emission e46 aren't as picky as the m56.

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The precat o2's should definitely not be pulled out of the stream and if only 1 sensor is out of stream the other sensor is going to read vastly different especially considering you are using a 90 degree over a straight regular defouler. Both precat sensors should be reading pretty close to each other at all times. This can be verified with a scan tool. Also when I did my headers my car through a code for oxygen sensors swapped. I do have a sulev vehicle so maybe standard emission e46 aren't as picky as the m56.

Sent from my [device_name] using E46Fanatics mobile app


Sent from my [device_name] using E46Fanatics mobile app
 

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Discussion Starter · #6 · (Edited)
Thanks for this info guys. As for getting rid of the 90 degree adapter, without it it one of the pre-cat 02 sensors is going straight into the other header. My post cat bungs are plugged and the post cat sensors are just unplugged and removed. Now im willing to make modifications but i dont have the experience or tools required so i could use some advice there. Any opinions on those no-weld 02 bungs that clamp on with a high temp gasket? Also I should probably mention, the car ran perfect before the headers and I've eliminated exhaust leaks. I got OBDFusion and a bluetooth adapter on order to get here tomorrow so I can shed some light on the happenings in my car.
 

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Discussion Starter · #7 ·
I would say that a pre-cat O2 should not be pulled out of the flow stream to read properly. Post cat O2's, that works fine but the upstream needs to see all the AFR changes ASAP and accurately.

I am about to do this as well and am wondering if you have any pics of which O2 bung needed the modification? Also which brand of headers did you use? My set I purchased for my 04 330Ci 6 speed is a Chinese mfg. # HD-BE4602
I bought the headers on eBay from the seller tcboverstock for an '01 330Ci. I don't have any pictures, however, on the particular headers I bought, I had to cut the post-cat bung down alot on the rear header which wasn't too big of a deal as it was threaded all the way through. Also, the pre-cat bung on the rear header had a bit of metal blocking the o2 sensor (dremel took care of it), and finally, the pre-cat on the front header required the 90 degree or else the wire would be right on the other header.
 

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wow i just looked at those headers on ebay last night (because they were so cheap0 but one review mentioned the post o2 location problem. Definitely not worth the trouble. I think I'm going to use the same set that Zander just dynod. the pro 1 they are 250 but they worked great on his ZHP with no tune
 
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