Hi guys! This is my first post, but I'm reading this forum few years already, so I'm not nube, and know pretty a lot about Z's.
I have a 350Z GT 2006 non/revup with a lot of bolt-on's.
Both my valve covers breathing to atmosphere. Intake vacuum port is not in use.
Here is the thing: I guess ECU assuming that some amount of air(vapor) have to get in the intake via intake vacuum port and making mixture with this extra volume in mind. I put the hose on the vacuum port with a small breather. As for me, car runs much better when intake vacuum port not capped. From another side, if ECU don't paying attention on that port, I prefer to cap it to have a perfect mixture.
Please, only facts.
And yes, I kill a lot of time looking for this answer, but nobody know that yet
P.S.: Sorry for my English.

 

Put the breather hose back on. You are venting air that the car thinks is going into the engine.

Plus I'm sure it would give you cancer in California.

 

If car really think so, it's have a sense to bring there a clean and cold air instead of hot oil vapor.
I got a Oil catch can, so don't worry, I'm not making too much pollution.

But still a question: are you sure that "car thinks" that there have to be extra inlet?





Here is my intake and vacuum port with a hose and breather

 

Yeah that's your problem. You're intaking air that isn't metered. You'd be better off just plugging off the port on the bottom of the intake. It still wouldn't be right but it would be much closer than where you're at now.

 

But what is wrong with air instead of oil vapor? Any proof that ECU not assume that this port bringing some air? I understanding, its behind of the MAF, but I think, Nissan engineers adjust ECU to count it even if it's not metered. Am I wrong?

 

You're getting much more air with your current setup than you would with the crankcase vent.

 

I guess you are right, because amount of oxygen in oil vapor is minimal. I know it's sounds stupid, but maybe somebody dynoed intake with capped and open port and have some numbers? I would like to see AFR , but I missing my OBD2 scanner. If somebody have it, and can check AFR with capped and uncapped port, it's will resolve very old mystery and will be very helpful for community.

 

Interesting, in for results for whoever can test this.

Side note Odesi, you're missing a lower bolt for your strut bar. You've just got plastic push clip there now that's not really doing anything.

 

It will be the same while cruising.

Ditch that breather setup. The OE valve covers are not meant to be vented due to the orifices ID's. If you absolutely have to vent to atmosphere, cut the crankcase balance tube in the middle and have all 4 ports venting.

 

So essentially you think your car runs better with a vaccum leak??

 

Captain obvious on duty)
Lol. I know there is a push clip, just once I was too lazy to adjust the strut bar before replacing the bolts and I shaved thread a little bit and don't want to destroy it completely by trying to screw it down as is. So I'll put it back as soon as I get the same bolt. Also I got a sway bar on the bottom, so I'm OK, no worries)

 

In this case, filter even bigger vacuum leak, if we will follow your logic.
How to create vacuum in something that have a 3" diameter hole?

And again: how would you call a bypass valve in any CAI?

 

It's not a vacuum leak. It's an intake leak.

It's not correct and it will throw the fuel map off.

 

the stupidity runs strong in this thread....

 

You absolutely have to close the intake vacuum port for reasons listed above (unmetered air, fuel trims getting fcked up).

You can leave your valve covers vented open though since that will just push crankcase pressure out of the motor. However, it's a better idea to have a catch can hooked up to the valve covers.

Pretty simple, really.

 

Sorry, I misunderstood you. In fact, this IS a leak. But I was thinking, maybe ECU assuming that extra intake charge volume that is being sucked from valve cover. I just overthinked it

 

Please help

I almost have same issue which is the rpm shaking or stumbling at low rpms with very slow acceleration after warming up, that is what is doing in the video


i went to a lot of garage and they never figured out the problem and changed a lot of things with no fix $$$$$


finally after almost now one year I found experience mechanic ,

he unplugged the passenger side breathing pcv hose from the catch can (( small black box that attached to the passenger side air intake )) and the problem gone !!

How the car is working properly when he unplugging the hose ( with leak ) and having the problem when it’s plugged properly

we didn’t drive the car with high revs when the hose was unplugged but the low rpm stumbling absolutely gone

the mechanic comment is that I have leak somewhere else, so when we plug the hose the built vacuum pressure causing the issue from that other spot leakage

any idea pleaaaseee

where is the problem any solution or it’s really somewhere leak like what the mechanic said ?

do you think plenum gaskets leak , valve cover gasket??