hum in idle speed regulator

[Peter Lucas <lucas@xxxx>]

Ever since completing my water pump replacement project, I have had a 
rough idle problem, mostly when the engine is cold
.
I am still working through the obvious possibilities, but in the 
process of doing so I noticed that
when the ignition is on but the engine is not running, there is a 
soft continuous hum coming from the idle speed regulator (this is 
*not* the buzz from the frequency valve). I have never noticed this 
before. Is this normal, or could it be related to my problem?

Any tips on diagnosing the regulator? If there is a problem, how 
does one differentiate between bad regulator and a bad ECU? Can I 
measure the electrical activity between the two? Well, I know I can 
do that, but what should it look like?

Thanks for any guidance.

--Pete Lucas
VIN #06703