Poor idle/running rich from bad o2 sensor?

[vpr131]

Hey guys,
After starting up my dsm, it idles pretty high and eventually comes down after about 10 minutes of driving. However, after this amount of time at a stop/idle, it begins to choke and go down to about 300rpms, almost die, and then come back up again. It will repeat this process until it eventually turns off. Also, when I am driving, if I go in to neutral, sometimes the rpm's will fall down all the way and the car will completely shut off.

I originally thought it was a vacuum leak (it may still be although I have checked most hoses), loose clamps, or even bad gaskets. I recently checked for codes and I found that the o2 sensor is bad. Could this be the reason for my bad idle and extremely rich condition. I am blowing lots of black smoke out of my exhaust upon hard acceleration. Thanks

 

[jordan99GS]

With a bad o2 sensor the ecu will lock itself in open loop mode creating a very rich mixture to prevent damage to the motor. So order and install the new o2 first, because it says it's bad, and go from there. I had a similar issue and it solved it for me. So start there and see what you're left with.

Also is your bov recirculated? And if it's not are you running a maf with a translator? You should update your profile with your mods so we can help some more

 

[c2ypt1c]

Might be the ISC and/or BISS...I'd check those first:

DSM ISC motor testing & Replacement - YouTube

I found that the o2 sensor is bad.

Front or rear o2?

and a boost leak test goes without saying...