Honda Repair: 1991 Honda Accord - Air Charge Sensor, coolant leaks, vacuum leaks

Question
My daughter's 1991 Honda Accord keeps reving up and down repeatedly at idle.  When I disconnect the connector to the air charge sensor, it idles smoothly.  If I simply replace the air charge sensor will this solve the problem?

Answer
I think you are referring to the "Cold start valve" or the "Idle air control valve".
In either case it may or may not solve the problem, for several reasons.
1)Make sure you have adequate coolant in your cooling system and that there is coolant flow.
2)Make sure there are no coolant leaks anywhere.
3)Make sure there are no vacuum leaks. You will hear an abnormal hissing sound when engine is idling.
4)Make sure that TW (Temperature Water) sensor, as Honda calls it, is operating normally. This is the sensor on the right (Passenger) side of the head witch I believe is the one with the green plastic around the pins, in front of the sending unit.