I am currently working on a similar problem with a 1990 honda accord.When starting cold it goes up to about 2000 are.P.M.S and then it starts surging between 850 to 2000 until it warms up.I plugged off the brake booster checking for vacuum leaks and it stopped surging.I replaced the booster and now it surges only a third of the time.Apparently this has helped.The cold idle is still too high,around 2000.It should be about 1600.I checked the air starting valve and found that the diaphragm on the
Valve is leaking.The manual says to replace if leaking.I will be installing a new air starting valve soon.Maybe this will fix the
Problem.Ill post the results soon.