ab_sherm

Ive finaly fixed my stall/rough idle issue by connecting the pcv back to the intake manifold. Before, I was running a catch can on the breather side and capped the pcv side and Ive noticed the car would stall out after warm up and would run fine after start it again. After a track day of running this set up, Ive noticed the car would stall at every stop lights. So i got down to business by replacing the TPS, MAP, IACV, injectors, did a valve adjustment and idle relearn . No major improvements from those but after routing the pcv line back to intake, it idles fine and wont stall at all. I now run dual catch cans with the pcv routed back to the intake. I was wondering if anybody else had this issue with capped pcv? Im kinda puzzled to why my pcv needs to be connected to run properly and some owners dont. Yes i know we have a learning ecu but im still wondering why it ran fine with the capped pcv for a while and decided it needed it back lol. Could it be the crank pressure? Idk how the Ecu would react to that via what sensor

Jack Mazza

I had the same issue I vented pcv(with or pcv still installed) to vented catch can along with breather and it would just die at idle. Other people don't seem to have this issue. Is it because there is a vacuum leak somewhere? I routed pcv back to IM. With yours does it reduce blow by oil with just breather to catch can?

B serious

....In general, you should really understand how something works and also verify any advice that you take.

If the PCV would be better off just plugged up, the car would have come like that from the factory. Right?

Why on earth would someone just plug the PCV? And why would you take that advice?
It would be like if you had diarrheas and someone told you to resolve it by just plugging up your bum.

When your car was having issues, what did you cap off an
d where?

And how is your catch can plumbed currently?

There's no crankcase pressure sensor. The crank case pressure is relieved by the PCV valve. Its a one way valve that vents crankcase pressure. The breather allows for expansion as well as suction.

B serious

??

Did you run your PCV and breather into 1 catch can and then plumb that catch can back into the intake manifold vacuum? That would create a massive vacuum leak.

Why are you even installing a catch can? Are you tracking the car and having oil slosh? Or....?

Jack Mazza

No, I vented both to atmosphere. Both to a vented catch can. I had researched and saw plenty of people venting both to atmosphere, Rob robinette capping pcv, or doing a seperate catch can for pcv and keeping it closed loop. My issue is that when both are vented woth IM capped, and intake elbow capped. The car would die at idle. I researched and saw very few people had this issue, and many people seemed to be running both vented with no issues. I replaced pcv line to IM today, and it ran fine. I could run a closed loop on pcv and try that. I mainly track the car an notice some oil burn after events.

B serious

Advice on catch cans..

Firstly....don't install a catch can unless you absolutely need one. There's no reason that a traditional, port injected NA car needs a catch can.

S2000's have a semi unique issue in which, some oil gets trapped above the valve cover baffle on hard right handers (especially if preceded by a hard left hander).
That oil then pukes its way out of the valve cover ports (PCV and breather) and gets sucked into the intake tract, which can cause really bad issues.
This issue typically only happens on a race track. I've never heard of it happening on the street.

That doesn't mean it needs a catch can. It means that a catch can is probably one of the more simple bandaids to preventing this issue. The catch can also has the most downsides to any of the other solutions.

If you do decide to go the catch can route, plumbing it properly is important.

One can for the breather.
This one can be vented to atmosphere or it can be recirculated to PORT side vacuum.
The suction port on the intake tube has to either be plugged or have a filter put on it if it's not used for recirculation.

The other can should be for the PCV valve.
This one can be vented to atmosphere or it can be recirculated to manifold or port vacuum, as long as the PCV valve is retained.
The intake manifold suction port has to be capped if it's not reused for recirculation.

You'll also want some way to drain the cans often.

That's basic plumbing info, which is where 99.9% of catch can solutions stop.
This makes it a "race only" part and it requires maintenance.

But that still doesn't solve all the other issues created by catch cans.
You'd need to heat the can via some sort of coolant bypass tubing.
And you'd want to drain the can back into the oil pan, usually by using a 1 way valve and a pump.

TLDR? Install catch cans only you need to do it and have decided against the valve cover baffle mod, or have run out of latitude using valve cover baffle mod. Don't plug the PCV. I think Rob revised his setup after he discovered that plugging the PCV was not resolving his issue.
If it was meant to be plugged, it would have been plugged from the factory. It's not meant to be plugged.

B serious

Is your PCV valve clogged or something?

Reading what you've done isn't ideal, but wouldn't cause the car to not idle.

Jack Mazza

I am not sure on the PCV status in the car. I am going to replace it and try again. When I do it I will perform a vacuum leak test on everything I have installed, and see if anything comes back. I have narrowed it down to that being my issue for the bad idle when I have everything routed to CC.