Help: Pressure under oil cap, Oil consumption/loss

Solved: Pressure under oil cap, Oil consumption/loss, idle surge

I've recently been experiencing symptoms which would indicate a failed PCV valve, however, I recently installed the ECS Catch Can system, and shortly after that a brand new genuine PCV valve since this system still relies on the PCV to function. Since installing these, one of the issues I was having went away. Before the install, my car would rev in neutral before settling back to 800 RPM. Now it stays fairly stable at 750 RPM with no self-revving. However, I still have pressure behind the oil cap and my catch can fills up ever 400-500 miles driven. This is causing a drop in oil level, to the point where it barely registering on the dip stick after only 1500-2000 miles since my last oil change. Is this normal behavior or does anyone have any thoughts on what might be going on?

Solved!

Part 1 - Crankcase pressure & oil loss
After some research, I've come to the conclusion that the easiest solution for this issue is to reinstall the hose connection from the PCV valve to the intake rather than leave it blocked off. As far as I can tell, this is specific to the ECS catch can system but I'm not completely sure. After doing this, the can stopped catching 98% of what is caught before, however, the can is still functional under boost which is when it's needed the most. During N/A or idle, the pressure is vented to the intake. The only con to this setup is that the PCV valve is once again susceptible to failing.

Part 2 - Idle surge / self revving in neutral
This issue was resolved by cutting up my Injen intake and reinstalling the stock MAF housing in its original location using two 3" silicone couplers. I chose to leave the housing facing up for easy access. I purchased a used MAF in housing so I'm not sure whether my MAF was just going bad or if the maf wasn't seating correctly on the Injen intake or if the intake was causing the issue, but it's gone away and I've noticed the car runs better now.

Edit: Tip: It's important when trying to diagnose these issues that you perform a throttle body adjustment each time you change something. I did this through my APR tune. The ECU will try to compensate for any abnormalities over time, so even if you manage to correct the issue the car may still act off at first. It's best to reset and then access.

My assumption would be that your rear main seal went out.. check the area where your trans meets the engine and see if there's oil in between that's dripping.

I believe the rear main seal is fine. I don't see any oil leaking in that area, and my transmission was replaced about 2 months ago.

Edit: I removed the catch can system and reinstalled the pcv system tonight. When I pulled the dipstick or removed the oil cap, the engine ran a little rough. However, the is still a lot of air blowing out of either the dipstick or oil cap when removed.

The car is in the shop. Will report back when they figure something out...

Update: The shop has found a vacuum leak, but hasn't fully determined whether this is the entire cause of the issue or if it's even related.

Update!

The smoke test revealed nothing. There are no vacuum leaks, despite a code for a vacuum leak. Does this test also mean there are no boost leaks?

The current thought process is that the oil separator, not the pcv valve, has gone bad. This is a separate part of the same system but located under or to the side of the engine block, which I knew existed, but wasn't able to find much information due to the massive amount of info regarding the pcv valve. Any thoughts? Thanks!

kglewis1 said:

Update!

The smoke test revealed nothing. There are no vacuum leaks, despite a code for a vacuum leak. Does this test also mean there are no boost leaks?

The current thought process is that the oil separator, not the pcv valve, has gone bad. This is a separate part of the same system but located under or to the side of the engine block, which I knew existed, but wasn't able to find much information due to the massive amount of info regarding the pcv valve. Any thoughts? Thanks!

Click to expand...

Have someone follow you and coast for a while in gear so the engine starts to wind down then give it gas, have them tell you if you puff smoke, if so then it's valve seals which would cause oil consumption without any leaks since its goin out the exhaust. As for pressure in the oil cap, my best guess would be a faulty PCV, do you have a friend you can swap PCVs with to see if the issue still occurs with a known good one?

Ok FML.

My car has been in the shop for over a week now and has had every test run. My car is perfect. Apparently.

After the shop bypassed the catch can and reinstalled the PCV to stock, the car is preforming above what would be expected for my car especially considering the high mileage (140k). The vacuum system checks out, boost, compression, exhaust. There is no vacuum leak code now. And yet, when I was running the catch can system, it would blow air out of the crankcase, there was a code for a vacuum leak, and it would consume large amounts of oil, and it would self-rev in neutral.

For those out there with the ECS or any other catch can system... wtf? And again, I just replaced the PCV valve since this catch can system somehow incorporates the PCV.

Edit: So the pressure at idle is to be expected with the catch can after further research. However some of the other issues such as the vacuum leak code and self-revving in idle are not. I think my solution here is to reinstall the factory line from the PVC to intake manifold. It looks like this has also reduced oil consumption drastically for other vehicles that were experiencing different issues with this same system, as well as fix the idle vacuum issue. The only con is that the PCV with be prone to failing again, but since I have the latest revision, so be it.

If anyone has more info or suggestions, please chime in!