> a spike like that is almost always an ignition miss. If the cylinder
> misfires, the O2 goes to the exhaust where it's interpreted as lean, when
> in
> fact the A/F is unchanged.
>

Aha...and the light bulb goes on over my head! If there's no spark, there's
no combustion. No combustion, none of the O2 gets used up-- thus the
atmospheric O2 reading. It all seems perfectly obvious now!
Cap-rotor-plugs are new but the plug wires are old and crappy. They're my
primary suspect, as I never checked them. I bet I find one's bad and the
others not far behind. Time for new ones anyway. I should've changed them
with everything else.
--
John Bange
'90 Vanagon
"We'd tell a monkey how to peel a banana, if he said he was peeling one in a
Vanagon."