rb20 weird idle / boost.

[Nidd]

recently bought an s13 with a silver top rb20. runs pretty good but when i start the car no matter warm or cold it instantly idles around 1,800 rpm.

following the fsm to adjust the aac valve i unplugged it and the car ran normal. so i didn't adjust it just reconnected it thinking it was fine and went on my way. after about 10 minutes of driving it went back to high idle.

i disconnected the aac valve and it idles a little higher then before. 1,000 rpm range.

another weird thing i noticed was that with the aac connected i'm able to hit about 12 psi of boost no problem. disconnected it gets to 5 or 6 psi and stops. there are 2 vacuum lines that are disconnected. not sure if they might be an issue or where they go. previous owner had the bigger one blocked off but the idle was way to low.

if any one has any idea what it could be any help would be appreciated.
thanks for looking.

http://i149.photobucket.com/albums/s79/Demonboy021/IMG_20110831_121728-1.jpg

[Pandapants]

There are a couple of things that can cause irregular idles, and out off all the nissan motors, it seem like the rb20 suffers from it the most.

Check for boost/vacuum leaks. It sounds redundant, but just one loose coupler can go a long way. Tighten down all the intercooler clamps, miscellaneous vacuum hoses/ports are plugged, AND make sure the intake system is tightly clamped.

-Make sure your battery is charged.
-Make sure your tps is within voltage range; ~0.50v +/- 0.05v closed and ~4.0v wide opened
-Make sure the idle contact is engaged on the throttle switch when the throttle is closed; ~8-10v closed and 0v opened.
-Make sure your AAC is working properly; terminal 1 should have battery voltage when "on", and ~6-7v idling cold, and ~8-10v idling warm.
-Make sure the Air Regulator is not staying open; It should be open/half open at at ~20* C and fully closed at ~60* C. You can check by applying battery voltage to the regulator and visually seeing the shutter close. It should close within 7 minutes.

The vacuum lines circled lead to the charcoal canister. If the hard lines are connected to the manifold, then those open opposite ends need to be plugged. If they are not connected, it doesn't matter, as long as their respective vacuum ports on the manifold and thorttle body are plugged.

The boost issue with the aac unplugged/plugged, sounds like an air leak. When the aac is disonnected, the valve should fully close. That means boosted air that would usually go to your motor through the aac unit, no longer is. If you have a leak anywhere, the extra 6 or so pounds could be leaking through it/them. I hope that makes sense. Im in a little rush typing this.

P.s. What intercooler piping is that? Ive been looking for some that had a 90* curve like that.

[Nidd]

thanks, i'll check it all today. and the piping is from cxracing.