O2 sensor, installing one if it didn't originally have one

[Jmac700]

Ok so my 1990 m20b20 is running like crap, on full acceleration and coming down the gears is fine but tryin to drive normal there are so many flat spots and can kangaroo at certain revs

Also its quite an expensive drive, so its probably running rich, on reading theres so much to test/replace and some people end up replacing the whole engine and still not figuring it out

Anyway mine doesn't have an o2 sensor on the exhaust manifold as standard (unless someone replaced it with one without, but why?) the plugs there under the batt tray, if i fitted one and used it as if it was "standard" what would happen? Would it work/help?

[jonny323i]

Apart from the late tourings 4 pots not many e30s had an 02 sensor but the prep was there for other countries.
Like has been said before you need to check all the small stuff first the wiki is the best place for a step by step.
What mpg do you think your getting

[Jmac700]

Replaced the idle control valve and coil pack, checked tps and air mass few other bits, i've had a 318i and a another 320i which ran ok and pin pointing this 1 is getting annoying, i'm going to fit a wideband 02 + air/meter anyway and was just wondering if the o2 sensor could shortcut the problem, thanks tho i'll check wiki and do a full runsheet and go tick by tick

Mpg lol erm 20 if i drive like miss daisy 16 if i drive like boy racer

[jonny323i]

that is bad even for a 320I

[Jmac700]

Had this one about 5 years but a couple of years off the road because i swap between the bm and a vitara offroader, tried quite alot to get it running right, its annoying because when i tweek/change/clean something it runs good or different for a day or so then reverts, i'm at the point of loving the car still, hating the engine, think the near future will call for m52b28 conversion when i find the right donor

[Morat]

Have a look in the WIKI and go through all the settings/checks first, like blue temp sensor, air leaks, TPS, ICV...

putting in an O2 sensor will not fix any problems lurking around, may make them worse!!

This is the way ahead. Mine was the blue temp sensor, and it made a huge difference. You need to be methodical, any random tinkering will just make things worse and serve to mask the actual problem - making it harder to find.