Rpm goes up and down

[zz3po]

Hi everyone... need your experience here...
I have an m43 engine, last week was over heated and the head was damaged.
I send the head to fix it, and then installed it, replaced head gasket, some dry hoses, of course took out manifolds, camshaft etc.. during the process.
Now i turned on the car, the engine works smooth, cooling system works great... only issiue is the rpm works ok... then in a sec it goes to 2500, stay there for a while and goes back...
It happens also when driving, rpm goes high, like im pressing the gas pedal for no reason.
Must say that isnt happening all time, only once in one sec or something like that.
Hope u have any direction for me.
Thanks!

[colb]

Could be due to an air leak, as you have had the head apart recheck all the air hoses are sealing with their hose clips and none have holes or splits. If hoses look good then take off the Idle Control Valve and give it a clean with carb cleaner let it drain and dry before refitting it.
See if that restores it to an even idle.