Re: 1994? Grand Marque, sudden very high idle.
On Wed, 02 Nov 2005 07:58:51 GMT, Old Man <firstname.lastname@example.org>
>Daughter called for help. Increased idle started suddenly, not
>dropping engine speed at stop light. If left without brake, will
>reach about 20 mph. Stayed same when started after parked overnight.
>No help spraying linkage. When I see it later this week, will check
>linkage for frayed cable. Is there anything else which commonly
>causes high idle? Clogged PCV valve? Bad vacuum line? Bad
>electronic component? Rat nest under air cleaner? She states no
>symptom above 30 mph, and accelerator peddle does not stay down or
>appear binding. I just want to be able to test all causes, and save
>her a buck.
It is not likely a linkage problem although it is a good
idea to eyeball it anyway. You likely have either a vacuum
leak which usually occurs int the PCV circuit on those or a
dirty/bad IAC. The IAC can be cleaned but, they are many
times too carboned up to easily clean. Overnite soaking of
the valve end in a good throttle body or carb cleaner may
work. Sometimes, they require replacement. They are
usually available for around $50 or less if you can replace
it yourself. It is not difficult if you have a decent
assortment of hand tools. Sometimes, it is best to remove
the whole throttle body and clean the EGR ports at the same
time which is often needed on that vintage to correct or
prevent other problems. You will need a throttle body
gasket to do that.