Okay I am at wits end. Exhaust smell & bad O2 sensor

[bmwagn]

I am newbie when it comes to the e34 (1995 525it, with M50). I have always drove e30's. So here's the problem. Check engine light came on at 183k code 1221. I replaced the O2 sensor (BMW factory part), reset light went on about life. 194k check engine light back on code 1221. I have no coolant problems and no oil consumption problems but I do smell exhaust especially in the vents and and when I open the door after a short or long trip. Also before I changed the old one I noticed smoke occasionally seemed white but no real smell just exhaust smelly. The O2 sensor I pulled was slightly blackened with a eraser sized piece of black goo on the tip (it tested bad by meter). I am wits end and I am afraid that the new sensor will probably go bad. Any suggestions anyone?? Should I just go to bed and forget about it. Thanks in advance, Kelly Joe.

[billb]

I am newbie when it comes to the e34 (1995 525it, with M50). I have always drove e30's. So here's the problem. Check engine light came on at 183k code 1221. I replaced the O2 sensor (BMW factory part), reset light went on about life. 194k check engine light back on code 1221. I have no coolant problems and no oil consumption problems but I do smell exhaust especially in the vents and and when I open the door after a short or long trip. Also before I changed the old one I noticed smoke occasionally seemed white but no real smell just exhaust smelly. The O2 sensor I pulled was slightly blackened with a eraser sized piece of black goo on the tip (it tested bad by meter). I am wits end and I am afraid that the new sensor will probably go bad. Any suggestions anyone?? Should I just go to bed and forget about it. Thanks in advance, Kelly Joe.

Mass Airflow Sensor. Bought a used one for $75 and all is well again. Could also be throttle position sensor, crank position sensor, engine coolant temp sensor, fuel pressure regulator...host of things to try. Search this forum for posts by billb (that's me)...

[tim s]

my cats turned out to be blocked shut.
tim s.

[bmwagn]

Sir,
It runs great, no idle or midrange issues that I can tell. Just that exhaust smell and the old O2 sensor has me concerned. I will continue to search previous posts. Thank you