High idle problem on 87 5kcstq (2500-2800 rpm)

[Kneale Brownson]

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Have you checked for collapsed hoses associated with the ISV plumbing?  The
crankcase venting process "mists" all those hoses with oily crap that
causes them to fail from the inside out.  Maybe something is plugged up
between the vent pipe and the ISV, and when you unplug the ISV, it no
longer causes the high idle????


At 02:51 PM 11/21/2001 -0600, blarson at zeiss.com wrote:



>I have been experiencing a very high idle on my 1987 5kcstq lately.  The idle
>occasionally is normal, but usually is up around 2500-2800 rpm.  I have
>swapped
>out the idle air bypass valve on the intake manifold with a known good
>one, and
>the temperature senders on the coolant neck both measure the correct
>resistance,
>and have no corrosion on them.  If the idle air bypass valve is unplugged, the
>idle drops to normal.
>Has anyone else had this problem with another component other than these
>two?  I
>searched the archives, and these seemed like the most likely culprits.  Your
>help is greatly appreciated.
>Thanks,
>Brian
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