1991 Acura Integra

It might be your FITV. This valve is only supposed to be functioning when your vehicle is not at start up.

To test this valve, remove the intake pipe, you will see two ports (holes) in the throttle body before the plate. The lower one is for the FITV. At operating temperature(very important) put your finger over the lower port.

Is there vacuum there? Or nothing? If there's vacuum the valve is faulty. And there are ways of trying to internally fix it that I can explain if that is indeed the problem.

Another possible cause may be your IACV, vacuum leak or dirty throttle plate.

The very first thing I would do, would be a good throttle body service. Buy a can of intake cleaner, remove the intake pipe and spray in the idle ports infront of the plate, open the plate spray inside and the back of the plate. Make sure nothing is binding/sticking as well.