Hopefully someone can shed some light on this...

I have a 2000 accord 4 cyl 5spd.

I was having clutch hydraulic issues, needed to remove upper intake manifold to replace clutch hydraulic line along firewall (not a fun job). I thought I had to remove both upper and lower intake manifolds to replace this line, so I drained coolant. I was able to replace it after only removing to upper intake manifold as it turns out.

SO, for purposes of my question, I drained the engine coolant and took the upper intake manifold off which included all attached vacuum hoses and sensor connectors, then put it back together.

Just to make sure I put the upper intake manifold back together correctly, and it's a bit cold here in Canada anyways, I tried starting the car without coolant (I wasn't aware this messed with the MAP sensor at the time). As soon as it started, the idle shot up to 4500 rpm, stayed there a second, and came back down. This process repeated several times until I turned the engine off. I did some reading, and made some changes:

-I filled the coolant, and tried to get out any air I could with the bleeder valve and squeezing the upper radiator hose
-I removed the upper intake manifold and removed the IACV. I then sprayed the Idle Air Control Valve with WD40. The air valve now moves much better and shouldn't be clogged or stuck open in any way

I tried to start the car again, however the RPMS still shoot up, now to 4000 RPM, stay there a second, come back down, and repeat the process until I turn the engine off. I'm starting the car with a jumper because my battery is now dead if that makes any difference.

I'm at a loss here as to why the idle is shooting up like that, any ideas?

Thank you in advance for reading this, and offering any help!!!

 

So you had no ideal issues before you replaced the hydraulic line?

 

That's right, I've never had an idle issue before replacing the hydraulic line, but I'm sure the problem is related more to the upper intake manifold that I removed and replaced (all attached vacuum and coolant lines included).

I've tried blocking the idle air control port from the throttle body to see if the IAC valve is a factor, but it doesn't seem to be: it definetely has vacuum, and blocking it brings down the surging a bit, but not much, it still surges very strongly.

So, it still wants to surge, and has a leak somewhere that's allowing it to.

 

Yup sounds like something didn't get connected since this issue is new.
Do you hear a hissing sound when the car is on or is the old to loud to hear anything?

I'm not sure if that car has them or not. There are little white air valves which allow air in 1 nipple and out the other nipple only. Can't think of the name. Could be that one was hooked up backwards wince they look the same.

Do a smoke test if you can and check where the leak is coming from.

You did have a clean surface on the head and IM for a new IM gasket right?