Assuming you have engine we're thinking of, this is the IAC:
All electric, works off a "pulsed" signal from the computer.
The little can on the bottom is the "motor" that drives a rod back and
forth inside the body. The rod has a couple of roundish lumps cast
into it that are supposed to smoothly regulate the air going through
holes cast in the inside of the body, depending on the position of
the rod. When it gets gunked up, the valve stops regulating and
becomes more of an on-off switch, usually causing the engine speed
to bounce up and down from way-too-high to almost-stall as the
computer desperately tries to control the idle.
As stated, take it off (1 electrical plug and 2 different-size bolts), then
blast and brush the inner passages until they're clean.
PS: The EGR valve is that round can with the holes on the bottom, hiding
on the back side of the manifold. Yours may be reversed, as some models
had the intake mounted facing the other way.
Are we talking about the same part here? This idle air control
doesn't have a vacum connections on it. It has two cavities on the
bottom an a electrical connector. What do you mean check by applying a
vacum to test it? thanks!
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