Where is the pcv valve on a 2007 chevrolet van with 4.8 liter engine ?

Mike, on your Chevy PCV valve normally plugged into valve cover.
Check the attached links,instruction and guides, Good luck
"I hope this helped you out, if so let me know by pressing the helpful button. Check out some of my other posts if you need more tips and info."
99 Tahoe PCV Valve replacment
1999 Chevy Suburban PCV Valve replacement
https://www.summitracing.com/int/search/part-type/pcv-valves/make/chevrolet/engine-size/5-7l-350

It's most likely due to a clogged PCV valve or clogged/kinked PCV hose. I'll include a video showing PCV system operation.
I've seen this symptom many times on various engines, and the PCV valve was usually clogged/defective. A clogged PCV valve results in crankcase pressure build-up and fumes/oil exiting places on the engine that it shouldn't. A severely clogged PCV often makes oil leak/exit out of the dipstick, even with dipstick in place.
The good news is... if the PCV valve is clogged/defective, the "cure" is a very cheap fix. Usually less than $5.
PCV stands for Positive Crankcase Ventilation, btw.

But note that on some engines (those where the oil filler opening is directly above the rocker arms/valvetrain) it is normal to have a small amount of oil "spray" come out, as the rocker arms are dispersing oil thru their oil passage hole on top.

(Whenever posting vehicle questions, always please add the engine size/type. It helps in more accurate diagnosis.)
Also, please rate via the helpful button if you feel my answer helped you out. Also post back and let me know if this cured it.

3.8 or 3.1 liter? The 3.8 liter has a cover on the passenger side of the intake plenum. The map sensor is possibly mounted to the top. Twist the cover to remove. The pcv valve will be underneath, make sure you install the o-ring exactly how it was on the old one! The 3.1 liter is on the drivers side of the front valve cover. Let me know if you have any questions and I'll do my best to answer them. Thank you for using FixYa.com!

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

If Pcv valve is not working correctly car will run real bad starving for air. And check engine lite will come on. I would add one liter of Locus oil stabalizer and drive it, Sounds like it's about time for a overhaul. best of luck to you.

Most vehicles do have PCV valves. Check on the upper part of the engine, on the valve covers for the thick tube that leads to the PCV Valve.

Iv'e never heard of this one but it must have something to do with the PCV valve its soppose to draw a vacuum on the crark but not all of the time. Try unpluging the pcv valve from the engine but not from the intake manifold main vacuum line and put your finger over it this is when the vehicle is running See if the vacuum stops on the dipstick tube if it dose replace the PCV valve' Let me know what you find im interrested to know thank

Hi!!
The PCV valve is located on top of the Valve Cover, it is held in place by a rubber grommet and has a vacuum hose connected to it. The PCV valve can be easier to remove if you just pull the vacuum hose (with the valve attached) straight out and then remove the valve from the vacuum hose. Here is a picture of the PCV valve for easier identification.
A HELPFUL - 4 THUMBS - rating for this solution would be greatly appreciated. Thank you for using FixYa.

Hi!!
PCV valve located under engine cover, top of engine, mounted in passenger side valve cover

Fuel filter is located Under vehicle, passenger side, below seating area, front of fuel tank, mounted on chassis DON'T FORGET TO RATE THIS POST!!

where is the pcv valve located on a 2002 chevrotet suburban

if you fallow the hose comming out of air filter assembley it should lead you to the pcv valve the hose goes to the pcv and should come right off then you take the pcv valve out of the valve cover by just pulling it out and replace it with a new one