I can't claim to have the solution to your idling problem, suffering from
similar issues in my '84 as well. However, RE O2 sensors, here are a couple
of things to ascertain. First, make sure the sensor is grounded in some way
other than the tail pipe. I did this by using a copper wire connected to a
radiator hose clamp and thence to the engine and frame. Second, separate the
outside (ground) wire of the coax cable from the inside--even one strand
will throw everything out of whack. Third, and this is often overlooked, the
O2 sensor takes its sample of atmospheric air through the end of the copper
wire, just a tiny opening which, if clogged by crud or solder or insulation,
will throw the sensor out completely. If you're interested in sensors, and
who wouldn't be, Ken Lewis' site has a link to a in-depth article from a
part vendor. Good luck.