Cheers guys, new to this forum! Have a bit of a scenario for your inquisitive minds.
My E36 M50TU 325i has recently thrown an O2 sensor code, 1221.
The same day it started having a dippy idle, hesitation (ranging from mashing the gas pedal and having a 1-sec delay in warp speed, or to just having the intake sound like it's going WOT but the car barely accelerating) and white to black smoke from exhaust, depending on the time.
In my diagnosis, I've found the following:
No oil in coolant.
No coolant in oil.
Compression test: 210, 211, 210, 212, 213, 215
Lots of oil in my spark plug holes -- enough to sabotage the connection between the coil and the plug, no doubt leading to my intermittent power losses and hesitation... vis-a-vis, faulty valve cover gasket.
Replaced valve cover gasket, cleaned and dried plugs, and reinstalled. Had the valvetrain case open to atmosphere (but covered with the bonnet) on a rainy day on Saturday, for over 2 hours.
Went WOT a few times around the block, car still experiences hesitation/power loss condition.
Billowed TONS of white smoke in the process, with exhaust smelling damp like a rusty pipe, probably due to all the moisture collecting in the valvetrain case while open to environment...
Checked all vacuum connections, found one of the two vacuum hoses disconnected, on the bottom of the intake boot (post MAF). Reconnected and clamped, cleaned throttle body, lubricated cable and linkage.
White smoke went away after a few WOT bursts and 5 miles of driving, exhaust mostly clear, smells rich with fuel.
Hesitation/power loss condition GONE.
Hesitation/power loss condition all eliminated, seems stable.
Check engine light turning on/off in 20 or so minute intervals -- curious note: when light is on, car idles smoothly, exhaust clear - smells only slightly rich.... when light is off, the car idles fluctuates, gets quite dippy, and exhaust starts smoking white, smelling like a mixture of rusty pipes or so... Does not have an antifreeze smell, luckily.
So, in the end, I am pretty sure it is the O2 sensor only, however, I'd be open to other suggestions while I wait for its replacement to arrive.
Thanks for the help!