Sluggish O2 sensor oscilloscope signals?

[kenny56]

This is from a 1990 735 with 185k miles, but is technically generic to all the bosch dme cars. i put a scope on the O2 sensor and recorded the signals under various driving conditions.

Now my question is what is normal and what is a degraded or sluggish sensor signal going to look like on the scope?

At POT @ 3300 rpm i'm seeing only 1 or 2 cycles per second. The rich condition is ~ .7-.8 volts and lean is ~.1 or less. The rich condition dominates the duty cycle about 80 to 90% of the time with just a quick, short excusion into lean territory. i was guessing it would have been closer to a 50-50 duty cycle.

Sometimes the signal goes to ~0 volts, and the engine loses power and runs really rough and doesn't seem to respond to the throttle pedal. The check engine light flickers on until the engine clears and the power comes back, usually after pumping or tapping on the throttle after letting off. The O2 signal comes back to cycling at the same time that the engine regains power. When i dump the fault code it is "1222" Lambda regulation out of control range. If i disconnect the O2 sensor it runs rougher (limp-home mode?) and the fault code is '1221'. Tried another dme unit with same results. The O2 sensor was new about 30k miles ago.

The scope traces are in a 50kb word doc file format. Now i see that image files can be posted, so i'll convert the traces and post some tomorrow. thanks.

[kenny56]

This starts with coasting at ~3300 rpm with Closed Throttle, then going to Part Open Throttle at ~ 2 sec, then going Wide Open Throttle at ~12 -14 sec until the end of trace.