Just a thought. Older Accords (86-89) had what I think was called a
fast idle control mechanism that was basically thermostatic in nature
and ran on coolant temp with one sensor, I think. In failure (as a
thermostat fails) it would make the engine race at idle and with the
clutch depressed in the same RPM as you described. BUT not sure if
this/these cars have the same set-up. $40-50 bucks at salvage yard and
a DIY job if this is the case. Just a thought, but not sure of the
specifics.

KL