1998 honda civic idle issues?

It's a honda civic 1.6L vtec. Blew a head gasket about 2 months ago. Went threw the engine replaced radiator water pump timing belt thermostat spark plug cables and every gasket you can think of on the engine including the vtec filter gasket. Got everything pieced back together only thing I reused was the spark plugs basically because I'm out if money till I get paid. New fluids as well. Started the car after all this and it's idling odd. Jumping from 1000 to 2500 but when I turn on my a/c it lowers down and chills. Think it was from not running for so long and the fuel was sitting. But not positive. The timing and everything seems to be on point as we marked everything before taking it off. The idle is just really jumpy. Messed with the cables going to the intake and it quit for a bit but after turning car off and turning back on got the same issues. If anybody knows what I could do to get the idle to stay steady please let me know. Kinda stumped but hopefully I gave enough info. I'm curious to why it stops jumping when I turn the a/c on but once I turn it off it goes right back. Seems like it was much worse at first but got better after a test run.

Most likely You have a bad sensor or the computer (ecu) is failing.

I had the same prob on my 89 Integra, my mechanic was stumped then guessed, correctly the the computer was flaky (bad).

So you replaced the head gasket. But did you have the head surfaced for flatness? I notice you don't mention it. But if it isn't blowing steam the problem is probably something simple like a vacuum hose. Re-using the sparkplugs is no sin my son.