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1998 BMW 323 Oxygen Sensors

Tiny
CORDOBA57
  • MEMBER
  • 1998 BMW 323
Engine Performance problem
1998 BMW 323 6 cyl Two Wheel Drive Automatic

I have a car which apparently was rebuilt. All appearences (including VIIN) say its a 1998 323i Cabrolet. But, some things are a little odd.

I need to replace O2 sensors but I am finding online information that indicates the car *should* have left and right sensors on the exhaust manifolds. This car does not. It has one sensor before the catalytic converter and one after.

Advice?
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Saturday, September 20th, 2008 AT 11:29 AM

3 Replies

Tiny
BLACKOP555
  • MECHANIC
  • 10,371 POSTS
If the left and right o2 sensor connectors were spliced together into one and hooked BEFORE the convertor then that woudl have no effect on the engine whatsoever, just wont be as accurate with orrecting lean left and right conditions.

What I woudl do is drill and weld in o2 bungs and hook them up the way they are supposed to.

The last sensor is for convertor effeicency and has nothing to do with performance.
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Saturday, September 20th, 2008 AT 6:17 PM
Tiny
CORDOBA57
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  • 2 POSTS
OK, my base concern is passing emissions testing. This really looks like a "factory" installation. There are "plugged" bungs in the manifolds already. Since the car has passed OBD II checks in the past (the sensors are now >118K mi) I have to think just replacing the existing one(s) will satisfy the computer.
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Saturday, September 20th, 2008 AT 7:01 PM
Tiny
DOCHAGERTY
  • MECHANIC
  • 9,601 POSTS
The pre-cat oxygen sensors are for bank I and bank II.
Bank I is the first three cylinders and bank II is cylinders 4, 5, and 6. The sensors are located on the exhaust manifolds. If there is only one pre cat sensor on the car, there will probably be an issue getting the cat past smog due to OBDII criteria, I request you repost with the VIN so that I can know some more about the car. I have also E-mailed you a picture of the exhaust manifolds. Dr. Hagerty ♥
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Saturday, September 20th, 2008 AT 7:52 PM

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