1994 Chevy S10 4X4 Blazer 4.3L Vortec races at idle?

Answer 1

Sounds like it could be a bad idle air control valve motor, throttle position sensor, or a vacuum leak up to and/or including a blown intake manifold gasket.  My '93 S10 Blazer 4x4 with the 4.3 Vortec had a blown intake manifold gasket and it raced at idle like there was no tomorrow due to excess, unmetered air being pulled into the cylinders via the vacuum leak created by the gasket failure.  Just replaced the lower intake gaskets and now it runs nice and smooth, no more racing.