MPG with a bad o2?

[mpbmw318is]

How much would a bad o2 sensor hurt my mpg by?
What else does it hurt? Mine may be out. (damnit)

[kitM3]

i was getting like 16-17mpg

[mpbmw318is]

What do you have? 325?

[Stockman]

just a guess... but maybe an M3 since it says it in his nick

[mpbmw318is]

all right so I'm a wee bit blind. . .
sheesh. . .:ponder:

[kitM3]

Yeah I got a 97 M3, got the O2 sensor fixed and am getting like 20

[318Shawn]

Is there a way to test your O2 sensor?

[bungy42]

Well, you COULD crawl under the car with a miltimeter with the engine running and test it, but I wouldn't recommend it. Why don't you just ask the computer? The procedure is at this website:
http://www.bonnevillemotorwerks.com/fault.html

[318Shawn]

Thanks for the link. I saw that link along time ago and forgot how to do the check.

[318Shawn]

Does that test even have the O2 sensor check? I did the test and no faults found but I looked at the list of faults and I didn't see the O2 sensor listed. Could my sensor be busted and not show up on the test?

[bungy42]

Yeah, they call it the EGO sensor (Exhaust Gas Oxygen). It worked for me. Mine was intermittent. The light would go on for a few days, and then turn off again for a week or two. Finally one time it stayed on long enough for me to pull the codes out of the computer.

[mpbmw318is]

You guys are talking about obd-II tho, right?
having a 94 I got good ole obd-I

[mpbmw318is]

Bungy- I got the code fault and unless I read it wrong (1211) its says the dme control unit. uhhh, whats going on there?

[bungy42]

I dunno. That sounds bad... I've only ever seen 1221 (EGO sensor) on mine. I have no idea what the DME control unit is. My car has OBD-I, also. Anyone else seen this?