Author Topic: O2 sensor question (Read 7190 times)

mwilderl · « **on:** June 07, 2011, 01:07:20 PM »

Is there a difference between the O2 sensor in the e30 and e36? I'm finishing up putting an m42 into my e21 and am getting ready to have an exhaust system put on. The only thing i saw was that the wire lengths are different.

Thanks!

sqlpython · « **Reply #1 on:** June 07, 2011, 11:23:53 PM »

You will see that if you check on line parts suppliers that they are different.
The sensor is not based on body type ..E30 vs. E36 but on engine and year of engine. Compare part #s that should confirm the difference.
Buy the correct Oxygen Sensor.

bmwman91 · « **Reply #2 on:** June 08, 2011, 12:36:56 AM »

The sensors themselves are most likely identical. Most Bosch narrow-band O2 sensors behave identically. However, you SHOULD try to match up the O2 sensor to the ECU it was designed for. Between the different M42 cars though, the sensor should be interchangeable.

mwilderl · « **Reply #3 on:** June 08, 2011, 01:42:09 AM »

alright, thanks! i guess i'll be getting the earlier model then, although i feel like i'm paying more for just another foot or so of wire.

DesktopDave · « **Reply #4 on:** June 08, 2011, 12:05:15 PM »

I heard that pre & post-cat models are different, but I have no solid evidence. Wire length and connector are definitely the only difference in a vast number of Bosch NB sensors.

M5wanaB · « **Reply #5 on:** June 08, 2011, 12:37:42 PM »

they make a universal one that works for a lot of BMW's that has an extra long harness to work on several models. its much cheaper than the m42 specific sensor. part # is 13108

jrobie79 · « **Reply #6 on:** June 08, 2011, 11:19:41 PM »

i read somewhere that you can use the cheap 25 dollar mustang O2 sensors and just splice them into the existing lines? any troof to this?

DesktopDave · « **Reply #7 on:** June 09, 2011, 07:32:02 PM »

Any Ford four-wire should work, most recent V8's have them installed pre-cat. They're the same Bosch sensor. I've heard the post-cat one is different, but I have no really solid proof off-hand for that.

I'd highly recommend soldered splices & heat shrink tubes for a reliable connection. Keep the splices at the end of the wire so that the exhaust heat won't weaken the solder joints.

mwilderl · « **Reply #8 on:** June 09, 2011, 09:48:23 PM »

would a 91 have the O2 pre or post cat?

monty23psk · « **Reply #9 on:** June 09, 2011, 10:25:48 PM »

on a e30, it is post. Not sure with e36.

mwilderl · « **Reply #10 on:** June 10, 2011, 12:02:14 AM »

so what ECU you have determines whether it is pre or post? The m42 i have is in an e21 now

bmwman91 · « **Reply #11 on:** June 10, 2011, 01:46:26 AM »

All E30 O2 sensors are PRE-cat (as in installed UPSTREAM of the cat). Post-cat sensors were brought about by OBDII cars.

monty23psk · « **Reply #12 on:** June 10, 2011, 09:53:00 AM »

Quote from: bmwman91;104470

All E30 O2 sensors are PRE-cat (as in installed UPSTREAM of the cat). Post-cat sensors were brought about by OBDII cars.

Oops, yes they are pre-cat. I was thinking pre and typing post. lol

mwilderl · « **Reply #13 on:** June 10, 2011, 01:57:58 PM »

Alright, if the post cat O2s weren't introduced until OBDII then i think i will go for the cheaper m42 sensor. I don't have an old O2 sensor to steal the plug from and use a mustang O2 sensor so that option is out and i don't want to mess up the wires. Another thought I've been having is using a wide band sensor, but i'm not sure how much work and money that would take and at this point i really want to get my car back on the road.

bmwman91 · « **Reply #14 on:** June 10, 2011, 05:44:21 PM »

A wide-band O2 setup is cool to have, and isn't really too expensive. The Innovate LC-1 is like $200 with the controller & sensor. However, wiring is not exactly straightforward and how you ground it is absolutely CRUCIAL. I had my car running like crap for years until I figured out that it was due to a grounding issue. I can put up a how-to here since it is not all THAT complex.

Unless you will have some sort of need for a WB setup though, stick with a stock NB one.