Power FC questions (S15)

[sean350z]

First off, VTC. My neutral position switch wasn't hooked up before and at cold idle I'd see VTC "on" in neutral. So I wired up my neutral position switch directly to the ECU but it didn't seem to fix the problem seeing as when I rev the motor in neutral the VTC kicks on at 1050rpm. Ok not a big deal, it's probably my switch is busted.

Secondly, the IACV. Is the IACV vehicle speed dependant? I did idle learn after re-intialization for the stated 30 minutes and the idle is very smooth and solid. It's weird, at cold start up my idle is around 2000rpm and stays there until exactly 60C when it drops to 850rpm and is very very smooth. Ok that's weird but it doesn't bother me too much. The thing that's weird is a hunting in the rpm while in neutral coasting to a stop. It seems when going down a hill in neutral my idle rises as my speed increases. Almost like the IACV is controled with the vehicle speed and it's doubling it considering I have a US S14 speed sensor in a S14 tranny piped into a S15 SR ECU. Or could this problem also stem from the neutral position sensor not working properly?!?

Again, the above problems are not detrimental to the car or the way it runs in anyway. It's more of a "man that's weird" type thing and me being anal I want to fix it.

Should I get a new neutral position switch and try it?? Anyone with similar issues with the PowerFC?

Thanks guys.

[Monooxide]

From my current understanding of the PowerFC there are settings in which you can control Idle by the Water Temp. Sensor. Look into those settings. I bet its set to idle like that until you reach that temperature. You should be able to change it to whatever RPM and temp.

[JohnC]

Had the same hunting problem with my car after pfc install. I have the S14 slanted SR just like in your S15. I did not have the nps attached and after I connected it guess what? problem was still there. How I solved it is this way.
Take the IACV off, soak it with carb cleaner and lots of it and reattach it. I used almost 2 cans of carb cleaner before the black crap stopped
coming out of the valve. Solved the hunting issue. I would suggest you get a new gasket just to be safe. I kept the old one since the problem went away.

One other possible solution would be to check you BOV. is it stock? if so they have a tendency to leak. check that too

[sean350z]

I'll clean out the IACV tonight...

I have a OEM mitsubishi evo blow off valve recirculated and it holds boost very well. It does leak at idle but since it's recirculated it shouldn't matter really because the throttle plate is closed at idle when the IACV is controlling the air flow.