Just finished installing a new head gasket on my ls/vtec. I had the head resurfaced, cleaned, and a 3 angle valve job done at the machine shop. Now when I start my car, it idles normal until it's fully warmed up and then it starts to idle at the first line on the tach then up to about a grand and back and forth. It seems to drive good though. No CEL. I know all the sensor plugs are in the correct spot. Timing is dead on. It also sounds like it has a slight misfire. It idled fine before I pulled the head.

I have heard that it could be caused from a dirty IACV, dirty throttle body, FITV may be stuck, and possibly from needing a valve adjustment.

Here's the specs on the motor:
B18A1 block
B16 head
SARD FPR
Cometic .051" MLS headgasket
PCT (CTR) Pistons
CR is about 12.5:1 (bought a thicker hg to lower the compression)

 

Clean your IACV, make sure you bled your coolant system properly

 

+1 hunting and roaming idles are almost always that iacv i just recently had that problem with a steady high idle after it warmed up. Just clean it with brake parts cleaner and make sure its dry before reinstalling it

 

cleaned iacv and fitv, coolant is bled

 

gotta get the valves adjusted for sure.... the rockers are more likely than not in there original positions and plus with the machining now things are changed... but it also sounds like a vacuum prob.. see what most people dontknow about the IACV is that its ran by current , not coolant ( coolant is only to keep springs from FREEZING stuck,,, wow really????? yes ))

and it ANTICIPATES any LOAD put on the engine. CLutch ac PS ELD alt Vaccumm.. so that means the ECU drives idle (1988+ hondas. with IACVs _)

... so you may have your Power steering switch disconnected,,vacuum leak, dirty IACV
, or you need to set the idle, by unplugging the IACV, start engine, and adjust bleeder screw on teh throttle body, then plug back in and adjjust again.. GL