I replaced the O2 sensor and problem resolved. I repeated all measurements and even replaced the failed sensor to verify my findings.

I want to thank you all and a special thanks to Elektri for the info in last post. I always assumed that the CIS-E module was microprocessor driven. Analog computers were vintage technology by the time 1986 had rolled around. It is indicated from what I have discovered in my 1986 unit that no range limiting is done on the O2 input signal because the negative values sent it into a stall when it switched into closed loop.

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Dionysius