O2 sensor location

[Supreem]

Hi all,

I've searched the board, but to no avail.

Can anyone tell me where to find the O2-sensor?
528i from May 1980. It should be there, right?

Thanks!

[Mike W.]

Your location suggests Belgium so no it would not have one, I'm fairly certain only US spec cars came with an O2 sensor. Even in E28s, only the "green" engine cars came with O2 sensors.

On US spec cars they used a single downpipe from the manifolds to the cat and it was mounted in that downpipe, several inches below the flange connecting it to the manifold.

[Supreem]

Thanks for the reply.

I was under the impression that from 1980 onwards, the e12 was fitted with a lambda probe.
I guess I'll have to look elsewhere in order to find out why I'm doing 17l/100km (16-17mpg), and that's on mostly highways. Is this consumption within the range of what's normal?

Thanks!

[Mike W.]

My math says it's more like 14MPG, at least on US gallons. No, that's not the norm. Mostly highway should be more like 12l/100km or closer to 20MPG on US gallons. When my first E12 was our vacation car in the 90's I was getting 21-22 MPG, mostly highway, but some very slow in town traffic too. Assuming it's running well and not misfiring or anything it could be such things as retarded ignition timing, a bad fuel pressure regulator, a bad FI coolant temp sensor, (the one with a plug, not the single wire one that works the gauge) or a bad AFM. (Air Flow Meter) Almost forgot, a leaking cold start valve is always mentioned in literature as a possible cause although I've never seen one.

For reference sake some good resources are https://www.realoem.com/bmw/ which lists all the parts in a breakdown and is usually, but not absolutely correct, and https://www.bmwtechinfo.com/repair/main ... Repair.htm which is the factory manual available online. The latter is US car specific, but most things are pretty much the same.

[maybeillbuyit]

Very interesting info Mike, as always. I recently calculated my fuel economy and got about 15.5 L/ 100KM which I considered not too bad considering I just got my car running after 30 years. I drive with a fairly heavy foot in this car because its a lot of fun and I also do a fair bit of sitting in bumper to bumper traffic or stop light to stop light traffic. I guess theres always room for improvement and it is an indication of engine health which I know in my car I suspect the valve guides are fairly worn as it blows a big puff of oily smoke when warm after sitting 10-60 minutes.

Also my car has not O2 sensor, I just removed all the thermal reactor stuff.

[Mike W.]

Very interesting info Mike, as always. I recently calculated my fuel economy and got about 15.5 L/ 100KM which I considered not too bad considering I just got my car running after 30 years. I drive with a fairly heavy foot in this car because its a lot of fun and I also do a fair bit of sitting in bumper to bumper traffic or stop light to stop light traffic. I guess theres always room for improvement and it is an indication of engine health which I know in my car I suspect the valve guides are fairly worn as it blows a big puff of oily smoke when warm after sitting 10-60 minutes.

Also my car has not O2 sensor, I just removed all the thermal reactor stuff.

The US spec 530i's were much thirstier than 528s. Removing things such as the air pump and reactors would help, but what about the EGR? The O2 sensor really helped on MPG, plus you probably still have a 530 distributor which I don't believe had as good an advance curve. Even the electronic ignition over the old points system helped a bit. Worn valve guides, or much more work/old/hard seals will create oil consumption, but not really affect MPG unless it's so bad it's causing misfiring. Lastly a heavy foot and heavy traffic can really take it's toll. Taking all that into account I don't think the MPG you're getting is all that bad. Not good, but not awful and to be expected.