Reddit mentions: The best automotive pcv valves & accessories

Felpro makes a really great replacement gasket that’s reusable and never leaks. The 4.0 has a ccv rather than a pcv system and I always replace both vents and grommets (and the little tube connecting the rear vent) along with the gasket when I get another Jeep (I have 6 right now).
Rear crankcase orifice vent is dorman# 47057: https://www.amazon.com/dp/B000JZI1U2/ref=cm_sw_r_cp_api_o1AQBb8PJSXPA

Grommets are both dorman# 42344: https://www.amazon.com/dp/B06XS8XYHJ/ref=cm_sw_r_cp_api_K2AQBbMPJ1Z33

The front vent is available in different heights depending on year/model but I think yours is a doorman 47079. In a pinch you can always buy 2 of the orifice ones and drill out the restrictor.

Dealer tech here; this is "off the record" but some Yamaha Ringfree . has worked miracles before. Typically sticky rings is seen on short-trip babied cars that never see high temp or high RPM, but given your mileage and consumption I'd give it a try.

Also chuck in fresh PCV valve in there, given the age I'd bet it's gummed up pretty bad. Should take you all of five minutes to do if you have a deep 19mm socket and a modicum of mechanical know-how.

That's part of your PCV valve/line assembly. GM Part Number 12558673 I believe. Here's an amazon link: https://www.amazon.com/ACDelco-12558673-Original-Equipment-Ventilation/dp/B00S0G0KTW EDIT Double check that part number. There's a few similar ones and though it looks right I may be incorrect, though the correct part number assembly would look similar.

Essentially you've got an unmetered air leak coming into your manifold via that crack. That can and will set a P0300.

$3. http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/PCV-Valve/_/R-MPF39207_0115628736

$2.50 http://smile.amazon.com/Mopar-5175352AA-PCV-Valve/dp/B006EI1BUU/ref=au_pf_ss_4?ie=UTF8&Make=Dodge|40&Model=Durango|303&Year=1999|1999&carId=003&n=15684181&s=automotive

My reader is busted so I'll get it reset again tomorrow, but the first time it came back within the same day. Maybe 2 hours of driving time. It's just so weird I don't have a normal idle feel yet the CEL is on.

I'm leaning to it being the fact that I cheaped out on a $40 Chinese PCV, but everything checked out on it from my non-professional eyes. I couldn't justify the $118 from VW Amazon or $150 from DAP

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Edit: I may try replacing the diaphragm first and seeing if that works. $20 , if not, I'll shell out the $100+ for the VW part I suppose.

does this work? ACDELCO 15123628

I went with the ac delco one. I don't remember a washer on there. It did have the clips.

https://www.amazon.com/ACDelco-25193343-Original-Equipment-Ventilation/dp/B010GOPTPU/ref=mp_s_a_1_1?keywords=25193343&qid=1567459712&s=gateway&sr=8-1

Happened with my 325i when I had one, this is what I replaced, might be different for an LCI

If your car has the EVAP fuel regeneration valve (https://www.amazon.com/Mercedes-w124-Regeneration-Valve-ventilation/dp/B00AHQIO5A)

this thing tends to stick and you don't immediately realize it stopped working. It basically takes petrol fumes from the tank and burns it up in the engine and this thing is a solenoid valve

Hook up 12V to it and see if you can hear it ticking on/off, if it's not take it apart and see if you can unstick it, otherwise go to a graveyard and find one

This has been the issue on mine, it messes up a lot

That's a PCV hose GM part #12590632. The entire assembly is $125 if you order it through a Chevy dealer but you can find it elsewhere cheaper. If its just the valve that's bad you should be able to replace that by itself. I only know this because I'm in the process of replacing the entire assy since it snapped behind the intake and leaks oil everywhere.

It's plastic on most new cars. It's also not available on the Cruze unless you buy it complete, meaning with the throttle body and all 4 injectors. You can still get one for ~$400, but that's a lot of money to drop on a cruze.

As for why they go bad, this is the fun part. Both the Intake and the Valve Cover have non replaceable one way check valves inside them as parts of the Crankcase Ventilation system, and both like to go bad.

Fairly common issue on lots of turbo cars, the VW/Audi 2.0 FSI motors have a similar problem with the valves going bad, but at least they are easy and cheap to replace.