breather hose???

[CFLmmaChamp]

top side of the rb20 there is a hose that comes from the manifold... is that a breather hose or what is it cause mine is just wide open and i have no idea where it heads to? could that be my idle problem?

[placham]

Here you go, all stock RB20DET


End on right side should connect to turbo inlet/induction hose IIRC (not that top pipe), some where between air filter and turbo.
That piece on intake manifold should be a one way check valve, under positive pressure in IM it should shut off.
Seen people do breathers and such, not a great idea on MAF setup, cause all that stuff is after MAF reads air inlet volume.
Leaving that open will give you false air, yeah would cause idle problems.

Matt.

[CFLmmaChamp]

could that be the cause for it to die at an idle?

[Gabes13]

Like placham said, the pcv is a one way valve that is open during vacuum and closed during positive pressures. If it's not connected to anything, or plugged at the least, then you'll have a major air leak. For reference, if i open the oil fill cap will my 20 is idling, the motor will almost choke itself off.

[Shocker]

Like placham said, the pcv is a one way valve that is open during vacuum and closed during positive pressures. If it's not connected to anything, or plugged at the least, then you'll have a major air leak. For reference, if i open the oil fill cap will my 20 is idling, the motor will almost choke itself off.

Really? sure there isn't something else going on there..

Hes only going to have a big a** leak if he doesn't plug the plenum. Venting crank pressure to atmosphere like you would be doing if you removed the oil cap should have little/nothing to do with how the car idles..

Gabe does your RB push a lot of oil by chance?

[Gabes13]

Push a lot of oil? You mean my oil pressure? It's really high on a cold motor, about 60psi. It'll drop to about 40psi after about 10 mins of driving. After that, it settles at around 20psi. WOT are at about 65psi. Im using 10w40 oil. fsm says 14psi idle and 57psi at WOT. Please tell me that's normal.

[placham]

I cant verify this on a 20 or any other RB. Mine is apart right now. But I have seen cars with MAF or VAF sensors die out or choke or stumble when oil cap is removed while its idling. Anyway why would you want to reinvent the wheel here. If thats how it was design just leave it that way. My friends RB26 had 2 cans with breather attached to it, but then again his running AEM stand alone, and I dont think he has MAF at least I dont remember seeing one.

OP if you dont feel like playing with hoses, put your finger over PCV and see if that helps,

Shocker, if you modify the PCV system where you separate intake manifold from valve covers, pulling oil cap shouldnt affect engine then I think. Like doing catch can set-up or similar I think.


Matt.

[CFLmmaChamp]

so do both the pcv and bov return air go into the turbo inlet pipe?

[CFLmmaChamp]

do you guys think the idle air control valve could be an issue? im just tossin things out there i got the motor from a s*** place in canada and it was not worth me saving the 400 some odd bucks

[placham]

Yes both should go to turbo inlet PCV and BOV

PCV work under vacuum, you wouldnt want to load your engine with positive air or boost. All PCV does is get rid of gasses and blow by from crankcase/engine so you dont blow your gaskets/seals.

BOV- stock runs recirculated BOV not vented/atmospheric BOV, thats why it recirculates back to turbo inlet.

Go after whats easiest to do first. And easiest way to troubleshoot engine is start with stock(like it came from factory) especially for swaps. Troubleshoot then mod one mod at a time, so that way you'll know what might be the problem.

BTW, try to see if you have check engine codes on ecu, should have red led that flashes code.

Download service manual from here(site) and it should be in there how to retrieve codes and what they mean.

As for IAC valve Im not sure, but it does work the idle circuit-never had to fak with it. If Im thinking right KA or Sr might be same parts but Im not positive on this. But they do get plugged up with carbon once in a while, look up IAC cleaning or something on here like I said its similar to SR and KA(mounting might be different IIRC). All it is, is just a electric motor that regulates orifice/needle to let air in. Guess you could check electrical wires to it and it-self but its definitely in the service manual.

Here's the link if you dont have this yet, http://www.nicoclub.com/FSM/rb/ , right mouse click and save to your PC, should be top one "R32 All engines", you kind of got to go through it and look stuff up for RB20DET, should be in EL-electrical section IAC and ECU codes.
Get back with your findings.

Matt

[placham]

P.S. let me know if u want me to take a pic of inlet hose, I got it around somewhere with the turbo, since I pulled both off while back.

And Nissan refers to IAC circuit as IAA and AAC valve.