3.5L Idle too high

97 Concord 3.5l 77,000 miles

Hi,
My engine really roars to life when I start it. The tach goes to about 2800
then slowly drops to around 1300 over maybe 5 seconds. It will stay around
1300 even warm. No check engine light, runs smooth. I made a half-assed
attempt to spray some throttle body cleaner in the two inlets but it didn't
help, but it never has been cleaned properly. Could this be the problem?
What are possibilities or what else could I check without consulting NASA?
I am pretty good at fixing cars, as long as they are over 30 years old.

Thanks for any ideas,
Dave

 

Surely it TB needs cleaning and hopefully no damage was done by your spray.

 

I doubt I damaged anything- mostly I took a brush and cleaned around the
plates to make sure they were closing ok. Am thinking of taking it in just
to have it cleaned and see if that helps. Could it be a leaky intake
manifold gasket? It does not look too hard to take off and that would be a
good time to clean everything.
Dave