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Art,
Yeah, but... I didn't find what I believe to be the correct info in the updated Bentley Errata. See my follow-up on my original message.
Per the greenbook, the default with O2 sensor disconnected (open loop) is 54 deg. They also specify a validation range of 49-59 degrees open loop. If reading outside that range, system is "defective" in some manner which could include idle mixture adjustment.
The greenbook later says that the range may be slightly lower than 49-59 degrees with O2 sensor connected (closed loop). Since this is a feedback system, if input conditions other than O2 sensor and mixture remain constant (i.e. temperature, throttle position, etc) then the optimum O2 value should be obtained in a "handful of tens of seconds". I'd venture to say 30-120 seconds. After adjusting my idle mixture to give something close to the "slightly less than 49-59 degrees", my dwell goes to almost exactly 54 degrees within 1-2 minutes. And it stays there. My digital dwell meter does not change by more than a tenth (0.1) of a degree once it zeros in on the 54 degree value. My idle is no "smoother than it has been in years".
Under driving conditions, my dwell stayed between about 45 and 62 and always went back to the 54 degree (+/- 2 or so) when things were otherwise steady. Coming down a freeway off-ramp to a stop, the dwell was in the low 60's as I decelerated and dropped to the 54 area within 10 seconds of being stopped.
I believe this setup to be correct for the 82 k-jet non-turbo without air pressure sensor and a C/V ignition.
When adjusted to be in the 40-50 deg zone, the driving readings would get pretty wild. During the "snits" or during the "flutter at freeway speed" the values were headed toward 70-80 then "went negative and over 100". I'd interpret this is being in such an unstable state that my digital meter couldn't lock on to a value. I'd also guess that the freq valve was essentially "stuck open" (actually driven to always open) by the control unit at this point. I had another control unit that behaved the same way, so we're not dealing with a faulty control unit.
When I originally looked at the dwell at idle, it was around 54 degrees if unchanged for a while. But, change the throttle and it would go up into the 60-70 range and stay there for awhile. I drove it with the idle mixture set to give a ~62-65 deg midpoint and experienced the same wild readings and erratic operation.
I'm not sure what changed recently than may have affected the setting. My mechanic said the airflow sensor and throttle body were quite dirty. Perhaps some of that crud (or lack of it) somehow changed the idle mixture setting enough to make the O2 loop unstable at times.
jl
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