Thanks to all for helpful ideas!
Oddly, my idle problem seems to have, at least temporarily, gotten better, now that Omaha has hit 91 degrees F today ...

Now I'm trying to figure out why my 15A aux fan fuse keeps blowing...

Will try the Pennzoil product at some point -- have tried Techron and BG 44K without lasting effects.

__________________
Steve
'93 400E