1988 Honda Accord, carbureted, 287K miles, recently when engine warms up, sitting at idle, engine races up to approx. 2500rpm and down to 300 rpm ( almost stalling) back and forth. Only way to get engine to idle normally is to plug air suction port in air cleaner.

 

sounds like you already solved the vaccum leak then. So if you plug the air intake it quits?
Definately sounds like a vaccum leak

 

ok..so it is a vacuum leak??..however...I should not have the air suction port in air cleaner plugged. What is the most likely cause?? or area to check for a vacuum leak??