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I just picked up a 2000 honda civic si with a d16y8 motor in it. When i started the motor cold it idled at around 1000 rpm for about 30 seconds the it raised up to about 1700 rpm for about another 30 seconds then once again it raised to about 2500rpm and stayed there. What would be causing this? Im totaly new to civics and need some help.

 
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Is there one of these? on your dash?

If so, go get it scanned.

If not, don't put your foot on the gas when you start it.

 
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Maybe your Idle Air Control (IAC) valve.

 
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I know the car has a blown radiator and the IAC is somehow controlled by the coolant but I don't know if this would affect this condition. I do know that if I reduce the fuel pressure or change the timing in the motor that it will idle correctly, but with the timing changed the car is very weak I don't know how changing the fuel pressure affects the power. Could someone till me what psi my fuel pressure should be regulated at?

 
Rep Power: 234

An extremely high, constant idle is usually the sign of a vacuum leak. Fix the radiator and make sure there's enough coolant. Also check for codes, Autozone does for free. Fuel pressure should be right around 40-45 PSI.

 
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Will be replacing the radiator today and checking the fuel pressure if this doesn't fix the problems I'll start searching for a vacuum leak. I have a code reader and will also read the codes and get back tonight or tomorrow with you guys. Thanks for the help.

 
Rep Power: 517

IAC stuck, vac leaks, throttle stuck open.
If the CTS isn't sensing accurate engine temperature because of low coolant level, then fast idle speed could happen.

Changing timing or fuel pressure only makes the engine weak enough to slow the running speed. This is NOT idling correctly.


Fuel pressure specs, Engine idling:
Without vacuum hose connected
except B16A2 engine:
260 - 310 kPa (2.7 - 3.2 kgf/cm², 38 - 46 psi)
B16A2 engine:
270 - 320 kPa (2.8 - 3.3 kgf/cm², 40 - 47 psi)

With vacuum hose connected
except B16A2 engine:
200 - 250 kPa (2.0 - 2.5 kgf/cm²,28 - 36 psi)
B16A2 engine:
210 - 260 kPa (2.1 - 2.6 kgf/cm²,30 - 37 psi)


I'd shoot for 44psi without the vac hose attached, and see where fuel trims end up at AFTER correcting the timing and everything else (on a stock engine).

 
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Well I got the new radiator put in and the coolant bled along with the codes read had a code for a mass air flow sensor. I think since I put the new radiator in the idle has stabilized some but it is still far from where it should be. I noticed when the car is running today a hissing noise... a vacuum leak searched and searched for a leak but couldn't find one I have a feeling that its a intake manifold gasket. As for the throttle blade being stuck open that was my first guess and it wasn't the problem. I'll continue to look tomorrow for a vacuum leak.

 
Rep Power: 517

You cannot possibly have a mass airflow sensor code.
2000 Civic does not have a MAF (Mass Air Flow) sensor.
Methinks you need a smarter scanner. Either the tool itself or the tool operating it.

Post the real code number. Hell, get the real code number and google it yourself.


Spray can of something flammable, like carb and throttle cleaner, spray around near the sound of the leak. The engine should do something noticeable if you spray into the area of the vacuum leak. Narrow it down this way.

Keep flammable stuff away from the ignition!
CAI can make a lot of sucking sound too.

 
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Haha I totally agree I have never used this code reader before and it is WAY smarter than I am.

 
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Well I found out that indeed i did have a leaking intake manifold gasket so I'll be replacing it as soon as the parts get in should be a couple of days. Hopefully this will get this thing back up and running as it should.

 
Rep Power: 517

Good luck, and be careful. Don't accidentally cause more problems.

 
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Got the engine back together today just gota pick up some new nuts for the header and it will all be back together everything went smoothly and should be running tomorrow.

 
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Kools.

 
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Well i got the engine back up and running today and the intake manifold leak is fixed but the high idle issues are not. I'm still getting that same hissing noise as before from the area around the intake but spraying carb cleaner around the area has no affect on the idle speed. I'm kinda stumped at this point. Any suggestions.

 
Rep Power: 517

Leave anything unplugged?
Check engine light on?
One of the bottom seals fell off of an injector. Don't laugh.

Start over, start from scratch as if it was a brand new problem.
Tap on the IAC, maybe it is stuck.

Use a length of tubing held to your ear as a stethoscope. Move it around, listen for the sucking noise.

 
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Well it looks like the problem is still in the intake manifold its just leaking in a spot that was hard to spray with a spray can. So I guess its back off again and hopefully this time something will turn out better. At least this time around I know what to do shouldn't be a big deal. Also I fooled around with this fancy code reader and got some codes that make since this time: P0122 throttle/pedal position sensor A circuit low input. P0135 02 circuit bank 1 sensor 1 and P0141 02 heater circuit bank 1 sensor 2.

 
Rep Power: 517

I would start with erase the codes.
See if they come back right away.
Maybe you turned the key on while stuff was unplugged.


TPS-is it plugged in?
Same for the O2 sensors?
All fuses good? Both fuseboxes?
Any ground wires you forgot to tighten up?

Next step might be real troubleshooting with a DVOM.

 
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I have the same problem with my 2000 civic, I have changed the o2 sensor, iac valve, intake manifold gasket checked for vac leaks, still no luck, it seems to be temp related, when its cold its fine and when its hot its fine, its only when its between hot and cold it happens?? any help would be great,

 
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Well I think that I've made some head way. I pulled the intake manifold again today and while cleaning the gasket off the intake manifold I noticed 4 small holes about 3/16 of a inch above each runner in the manifold that are not sealed by the gasket and these holes are ran directly into the intake manifold this is where the vacuum leaks are. I plugged these holes with magnum steel and will be putting everything back together hopefully for the last time.

 
Rep Power: 517

Wrong gasket? Non-factory gasket? Backwards? Different manifold? There has GOT to be a reason.

Inquiring minds want to know.

 
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The head is off a 1995 honda civic and the intake it off a 2000 so the bolt paternt for the intake is the same but the mating surfaces are diffrent causeing the problem. I feel really stupid for not noticeing this the first time but now hopefully it will be fixed. As for a curious mind what exactly are these holes for on a 2000 d16y8 motor?

 
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All I can think of is possibly EGR on a different engine. Really, I"d have to see all the stuff involved to be sure. Including the other engine parts.

 
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Well I got the motor back together today and it idles! Finally this thing is running as it should be. Thanks to all you guys for the help.

 
Rep Power: 517

Good to hear it, thanks for the update.