Hi, my 1998 Honda Accord V6 Sedan engine revs up and down when turned on initially until warmed up.

Here is a link to a video I made of what it looks/sounds like (tried attaching it but maybe 25mb is to large?). http://ge.tt/4TsawCB3

Has anyone ever experienced this, would really like to find the root cause.

Thank you!

 

Try cleaning your Idle Air Control Valve (IACV)

 

There's going to be a couple a little water hoses that go to the FAST IDLE VALVE , not to be confused with the ELECTRONIC IDLE CONTROL VALVE valve on the intake manifold. You need to very carefully disassemble this with the engine cold and clean it out. There is likely some Gunk stuck in there from coolant corrosion Etc that's causing poor water flow. You should also verify that you have the correct water level in the engine as well cuz this can also be an issue if it's low on coolant. That little idle air control valve has a wax pellet in it similar to your thermostat so it actually will allow more air to Flow by passing the throttle valve until that device warms up and closes the bypass air

 

Thanks! I wanted to double-check that the 98 accord v6 has a Fast Idle Valve? (I read that they stopped using them by that year - any chance you happen to have a reference to those hoses in a picture or video)?
Found this example on Fast Idle Valve cleaning


I found these video examples regarding the Idle Air Control Valve.

 

Thank you, I'll check that out!

 

Heres the parts information as an fyi.

Its a combon electronic idle air control valve and fast idle.
Idle speed control, referred to as
"Valve Set, Rotary Air Control"

 

Thank you!!