High idle speed, 4ksq....More data.

[Richard J. Andrews]

I would definitely start by checking all the vacuum lines (large elbow of 
Intake manifold & ISV junction on valve cover)
i would start by replacing the faulty idle switch...
might try disconnecting the o2 sensor and see how it idles...
but don't trust an external exam of these hoses... i have had them collapse 
internally while they still look new outside..

HTH!
rich
'86 4kq