I've been trying to get the lambda system working on my 1982 244 turbo. Right now, the frequency valve buzzes audibly with the oxygen sensor cold or disconnected. Once connected, it quiets down and the dwell drops to around 11 degrees. The O2 sensor reads steady at around .7 volts and does not fluctuate (tested with the o2 sensor still plugged in).

I've tried:
Testing all lambda system wiring per Bentley, checked good
Tested pressure differential switch, and thermal switch, checked good
Tested Freq. valve resistance, read 2.7 ohm, seems good
With O2 sensor disconnected, dwell reading is a normal 43 degrees
Replacing o2 sensor with a new one
Replacing Lambda computer with a junkyard unit

The only possible things I can see that might be wrong are a bad O2 sensor, or a bad computer, which seems unlikely since I've replaced both with to no effect.

I'm stumped.

Any ideas?

--
Eric, 1983 245 ti