Car bogs and breaks up when going to closed loop

[LGAFF]

My 91 runs well when started up in open loop, alittle rich, but as soon as it goes to closed loop the cars bogs and breaks up. The Left 02 will oscillate, but it drops down as low as .018 V for short spans ... there is no apparent leak, I changed the 02 with no change, I verified 12 volts at the power source(AC fuse is fine) and continuity with the ground, I also tested ckt 412, when I jumpered ckt 412 to ground with the car running it produced .020 Volts(manual says it should be under .200). There is also no check engine light.

Any thoughts? I am going to replace the connector and see if it improves

[Mikey]

What happens if you just leave the o2 sensors unplugged

[LGAFF]

runs in open loop and is fine

[Mikey]

Has the wiring been cut, spliced or repaired at any point?

[LGAFF]

It has not

[LGAFF]

ECM tested on another car and it was not the issue.... O2 sensor behavior was completely different that I see on my car.... back to the drawing board. Going to swap the right side and see if it changes....

[Paul Workman]

Your symptoms are exactly what I experienced (on my 95 LT1 car, actually).

When the O2 would toggle to "zero" volts, the ECM would interprit the reading as dead LEAN and the injector duty cycle would approach 90%. But, as a rule, there was no code set - no "check engine" indication - until several miles of running like crap and blowing black smoke from that side of the engine.

Swapping sides with the O2s verified the O2 issue. I replaced the O2s and that problem went away*.

*Well, I created another problem as well: I sealed the area on the O2 sensor wires where they enter the probe. BIG MISTAKE! As it happens, the O2 sensor depends on sampling the surrounding air in order to work properly. $80 later I discovered this little tidbit of info. I refrained from putting RTV around the wires at the entry port to the O2, and the problems ended there!

O2 "cross counts" should be roughly the same. IIRC, the last time I checked, my cross counts were ~ 400 ish each. But, if one is (say) half (ore less) that of the other, my tech manual source says it indicates a "lazy" O2 - one headed for the dumpster soon!

Marc Haibeck recently suggested I switch to the NTK A8D1B1 21003 O2s (as part of an attempt at eliminating another brand as the source of a problem unrelated to your specific issue) They seem to be working well enough for over a year or so now, And, NO lazy O2 or sticking at "zero" volts either!

[LGAFF]

I think my problem is solved, I kept looking at the DS o2. and after watching another cars 02s oscillate I noticed it was the PS behavior that was different. pulled the harness extension, rebuilt it and looks like my issues are no longer..... need to do some additional testing

[Mikey]

What was wrong with the wiring?

[LGAFF]

I am not sure if it wasnt getting the signal or if it was a power issue.... the PS o2 would stay in higher MV reafings going into open loop