Vacuum assisted PCV scavenging

[HCP2311]

I'm assuming you're a young guy with not much experience, not making fun of you. If my assumption is correct and you are interested in learning, find the yourself City college that offers automotive training. Again not making fun of you, from your posts does not seem you have an understanding of how things work.

I'm in my 30's lol and definitely do not have much experience. I did take ASE engines, transmissions and suspensions at Iowa western several years for fun, which led me to a bachelor's in mechatronics but my work experience is army medical. Idk how good the advice would be for recommending someone to college ASE classes because Iowa western has a pretty nice program, but those classes are strictly for sending techs into entry level positions for modern car routine maintenance. I've learned far more in the process of rebuilding this LC than any ASE program would ever offer.

What exactly seems off to you about this? Something HAS to be wrong with this PCV system. It doesn't make sense for Toyota to route TWO vents from the the same valve cover to two different places on the intake. And even if they did why does only one have a 1-way valve? Why can one be open without causing a lean condition when even the smallest crack in the other will kill the engine within 30s?

 

[azusa]

I totally agree with you that classroom knowledge won't get you far but you will get the basics, if you could measure the breather side you should have at the most half an inch of vacuum, well on the valve side you would have full engine vacuum. Imagine if you only had vacuum and no breather, you would probably pull in the oil seals at front and rear crank seals. On this system when you remove the oil cap or dipstick if everything is up to snuff the engine will stumble.

 

[HCP2311]

I totally agree with you that classroom knowledge won't get you far but you will get the basics, if you could measure the breather side you should have at the most half an inch of vacuum, well on the valve side you would have full engine vacuum. Imagine if you only had vacuum and no breather, you would probably pull in the oil seals at front and rear crank seals. On this system when you remove the oil cap or dipstick if everything is up to snuff the engine will stumble.

Stumble, but not die. Before I blocked the breather hose at the throttle body you could get maybe 30s of run time if you removed the oil cap. I don't have any fittings that are the correct size to measure vacuum at that hose, but it was significant enough that it could be heard by ear and felt by hand. From my understanding the air moving through the PCV valve and hose, into the plenum should be small enough for the ECM to either compensate and adjust the mix (Like newer engines) or run slightly lean (like older vehicles) but definitely not die in 30 seconds. For reference I just checked my 96 Tacoma, which stumbled and then evened out with a bit of a rough idle, then I checked my 09 rav4 which stumbled, revved slightly and then went back to a normal idle and just for good measure I checked my buddies' 16 Tiguan which barely gave any notice the oil cap was removed at all.

And you're right with no fresh air entering the valve cover to compensate for the PCV vacuum it should put the crankcase under negative pressure, but the way it was running before it couldn't have had any fresh air at least at idle because the breather hose was also pulling a vacuum. Like I said earlier when the engine is at operating temp some oil vapors/smoke can be seen coming from the filter I put over the breather port on the valve cover, but if you idle up the engine it starts pulling air at the filter.

 

[azusa]

Have you done any engine work recentlyTiming chain,cylinder head?

 

[HCP2311]

Have you done any engine work recentlyTiming chain,cylinder head?

All the above. Not me personally, I thought that was above my paygrade, I took the engine to Southern Cylinder and Head in Huntsville, AL for the rebuild. I did remove and reinstall the engine and trans myself. When I bought the rig early last year the head was off for supposedly a blown head gasket, but after I got the vehicle home and started working on it I found out that it had sand in cylinder 3 and 5 and the rings were ate up. I think the rig was probably driven into one of the brackish bogs on the east coast and flooded judging by some other water marks and rust lines I found in the vehicle interior. It was basically just a pile of parts when I got it that I've been trying to piece back together.

 

[azusa]

Your engine is running like crap, was it like this right out of the box?

 

[HCP2311]

Your engine is running like crap, was it like this right out of the box?

No it didn't run at all. The exhaust cam was 180 out of time and there was a vacuum leak at the plenum. (Which was my fault. I forgot to put a gasket between the two halves. Then the charcoal canister was clogged and the fuel pump stopped working. Then the IAC wasn't working right. Lol oh and the PVC was clogged at the hose and valve.

 

[azusa]

Wow wow wow, visual inspection Make sure all the injector connectors are snapped in, if you have a stethoscope while the engine is running make sure all the injectors are clicking. Check ignition timing, you probably need to verify the cam timing, making sure the two cams are timed to each other and making sure crank and cam gears are timed correctly also. If you can get access to a smoke machine, vacuum gauge, so we could see what the needle is doing. Let's start there.

 

[azusa]

Smoke and vacuum check before you remove the valve cover. But do the ignition timing.

 

[aztoyman]

Your vacuum SOURCE is the port after the throttle body in the intake plenum. The hose goes from there to the PCV valve on the valve cover. The PCV valve meters the vacuum to the crankcase as mentioned. It sucks the fumes out of the crankcase to be burned in the engine.

There needs to be clean air coming in and that is where the hose going to the intake tube prior to the throttle body comes into play. Since it's after the air filter, it's clean air and does not need a separate small breather. It doesn't need to be metered , the PCV already does it on the other side of this "loop". It's the fresh air source to the PCV system.

The vacuum will vary in the intake tube between the filter and throttle body based on TB position, engine load (RPM) and condition of the filter. But the PCV valve should still keep the flow going in the right direction. (Higher vacuum in crankcase) It shouldn't blow back in front of the throttle body when working properly.

I hope this helps.
Scott in AZ.