Intermittent buzz and poor idle

[Maurits Larson <Mel_Larson@mbnet.mb.ca>]

Twice during the last week my 87 5000q has made a buzzing noise at about
the 3000 rpm and over engine speed. It usually doesn't last for more than
10 minutes and I can't re-create it at will. Other than the noise it runs
fine, without a miss. I've checked some ground straps (as an earlier
posting had said) and found them ok (coil area and lh engine mount area).
Also intermittently my engine idle is rough when hot. Some days are worse
than others.
I'd appreciate any feed back from similarly striken 5 cyl non-turbo owners.
One more thing...what is the resistance of a good rad fan ballast resistor?
TIA,
     Mel