m50tu swap, possible fuel/spark issue(s)?

[indiejack]

Okay, got a few gremlins taken care of in my swap, running poorly though. 14mpg and sluggish in the mid-range, idle can be erratic at times (after warmed up will idle at 850-1400 or so - but not all of the time). Wondering if I should replace the ignition coils (well, wondering if that could be an issue before pulling each one out and testing).

There are a lot of little things I need to address in this swap, but the gist of it currently is that I was throwing an O2 code, replaced the old O2 sensor, reset ECU, drove around and after about 10 miles that CEL came back on and that leads me to believe that I'm pushing too much unburned fuel at the O2 (but I could be wrong as I'm not a mechanic and BMW engines are totally new to me).

If that doesn't turn out to be the culprit what do you feel it could be (given the vague and probably unanswerable train of words I loosely called a post above)?

[pdxmotorhead]

The O2 code is thrown by almost every error the engine produces. So its pretty much a red herring.

Vacume leaks will screw you up big time, also any leakage int eh input between the air flow meter and the engine...

Dave

[indiejack]

Found a vacuum leak, fixed it but not much better. I'll have to tear more into it this coming week.