Well, my 2000 civic Si is back together. I pulled the head off to replace a bad valve, and just simply put it back together.

But, curious....at startup, the engine starts, and then races to 4300 RPMs and seems to want to keep climbing but I shut it down immediately. What is going on? Is this some kind of control system that the ECU has power of, and is stuck in some loop??? Let me explain.

When I got the car, it had a check engine light, which did not surprise me. There was a valve with a hole in it...more specifically, exhaust valve. The check engine light had to be O2 sensor due to all the crap the exhaust was seeing....ie unburned fuel.

Is this issue as simple as unplugging the battery for awhile to let the ECU reset itself? I actually have not disconnected the battery yet through this week long rebuild.

I am new to this DOHC stuff. Please help.

EDIT: Can anyone provide an exploded view of the intake and its vacuum connections? Just an upclose pic?

 

check the obvious first..

look at your throttle body & make sure that your throttle cable isn't yankin that bish open & is caught on something.

Also, if thats not the issue, check your TPS for a false reading.. sounds strange but it's a possibility.

 

alright, I will check out the throttle body again.

Could it possibly be a vacuum line that I accidentally might have knocked off? Would a vacuum line of any kind yield this kind of result?

 

I would put money on a missing or cut vaccum line.

 

Well, hell. I think I found something, but I cant tell what connects to it. If you look at the back of the intake all the way to the right side, there is a small tube extending out from the intake, but no cap or hose is connecting to it. It looks like it should have a cap.

It is kind of like this...

What is it?

EDIT: Can anyone provide an exploded view of the intake and its vacuum connections? Just an upclose pic?

 

When attaching the MAP and TPS sensor clips, be careful not to cross the two. For some odd reason, Honda decided to use the same exact plug for the MAP and TPS, so it's very easy to cross the two. Just note, the IAT (intake air temp sensor, looks like a black probe) should be in the same mini-harness as the MAP sensor, so if you confuse the two, just see which one is tapped together with the IAT sensor. Make sure ALL vacuum lines are attached, and that the intake manifold itself is bolted down tight, this will save you the 2 hour headache I spent trying to figure out why my car would either idle at 6000rpm or jump from 1.5-3krpm.

 

I had a similar issue and it was because the old intake manifold gasket wasn't fully removed when putting the new one on, so the seal wasn't tight enough, so air just bypassed the throttle body through the leaks.

 

vaccum port....on USDM motors I do beleive that nipple runs a vac line to the emmissions canister.

 

awesome. You guys gave me some good leads. I appreciate the help. I will fix it all by tonight hopefully.

I was at the lake all weekend, and built an exo cage on a truck early saturday.

 

Well, I got the head retightened, and it did help. I found the line to the canister as well....done. Now, the engine revs from 1.5K to 2K RPMs over and over, once it is a little warmed up. Also, the check engine light is blinking continuously. I tried shorting the two lines at the blue connector under the dash on the right, and turned on the key, but the check engine wont blink a code...it just stays on solid. WTF????