Running issue 2008 Volvo XC70 3.2 230K miles

[Steve H]

OK, I have a head scratch-er of a problem with my 2008 XC70. No engine codes present. When you initial crank it after sitting for a while, the engine fires up sounds fine and then the sound changes almost like an intake that does not have a filter housing on it. A throaty air sound. Car has no power until you take it and blow it out and eventually it seems to run OK but not well. I have thought of injector leak down, I replaced the plugs after it was sitting for days. Smelled each plug and all was well and plugs looked really good to have 50K miles on them. I have check for DTC codes and none present. I just do not understand how the sound of the engine changes like it does, throaty sound like no air filter. The air filter is new and has been checked. Nothing in the housing or restricting the airflow. This one has me stumped. I have not checked the fuel pressure yet but no schrader valve on this one so you are reliant on the fuel pressure sensor on the end of the rail for accurate reading. I have replaced that part as preventive maintenance a very long time ago with an OEM manufactured part. I know on the back of the intake is an electrical plug in the center with a plate on the intake but I do not know that this does or what to call it. Any advice would be greatly appreciated. The car is nothing short of dangerous to drive and pull out expecting it to take off and it stumbles until you finally get it to tach up in rpms.

[Vova585]

Is your sound better with pulling dip stick up?
Hard to suggest something without having audio/video clip. But pcv diaphragm on 3.2 is a common problem.

[Steve H]

I did replace the whole PVC unit with a Volvo part a few years back and the car is not driven much but I have not thought about pulling the dipstick since this noise was not the normal high-pitched PVC noise. Thank you for the suggestion I will pull the dipstick and see if it changes the next time I start the car with the hood up and testing it

[pgill]

The intake tube has a sound suppressor that can leak false air into the engine.

You can disconnect the MAF and the engine will run on the MAP. And if the intake tube is the problem then the noise will be there but the engine will run fine instead of “NO POWER”

Let us know if this makes a difference or not so much.

I do have other ideas but I would start with the test I described above

Thanks

Paul

[Steve H]

Thank you Paul. I did not realize the car would even run with the MAF disconnected. I will give this a test tomorrow. I did go out this afternoon and had the hood up, then cranked the car but seem to run normal with no odd air intake noise. Like most things, it would not do it when you want to test something. While I was checking I pulled the dipstick up, while running, and the PCV made a scream sound. Is this normal for all 3.2 PCVs to do when you pull the dipstick. I installed the Volvo PCV unit in 2019 and have about 30K miles on it.

I have a curiosity question for you. In the center of the intake is a unit with an electrical plug on it that has some screws holding the plate into the intake. Would you know what this unit does?

[pgill]

The PCV should be silent.

Credit to VOVA585

You will need to start with the PCV.

The intake manifold has a variable runner length to give more power at high RPM and more torque at lower RPM.

That’s what you see on the intake manifold.

There are two flaps and the connectors look identical but they are keyed so that you can’t mix them up. (Ask me how I know…..LOL)

Your next step may be to replace just the PCV membrane. It’s simple but not easy.


Good luck

Paul

[Steve H]

Thank you Paul. It only made a noise when I pulled the dipstick when running and shut up when I put the oil dipstick back in. I have the Dorman PCV membrane kit on the shelf because I know they fail often so I bought it during a time I found a deal on it for $14.90 on Manufacturer Rockauto close out so I put it on the Volvo shelf. Thank you again.

[Steve H]

New Diagnostic Development. I decided to walk back out to my car. I cranked it and it ran as normal without the noise. I then put my finger over the hole in the PCV diaphragm cap and the valve started making a slight horn sound at the valve a little like it did when I pulled the dipstick earlier. Then all the sudden the loud air filter reverberation occurred when I let go of the hole. It lasted a brief bit but then shut up. That PCV kit is getting installed in the morning and Thanks to Vova585 and PGILL for your help. I will follow up.

[Steve H]

I changed out my PCV diaphragm, spring and cap with the Dorman part this morning. I first thought there was nothing wrong with the one that I removed but upon closer inspection it had a tear in the edge next to the thicker sealing ring of the diaphragm. I used a Popsicle stick inserted into the mid of the spring to hold it up while I lowered into place. That worked great. What did not go as easy as I thought it would, even after putting a little dielectric grease on the cap edges that you normally have to cut to remove the old cap, I did have trouble getting it to latch. I ended up using double dead blow hammers. One sitting on the cap and the other one striking it to get it to latch. Best I can tell now it is latched. I drove the car with no issues. Time will tell if this gets it or not. This morning I put my finger over the hole in the cap upon first start and it howled but I could not get it to go into the throaty intake mode as I did yesterday. I am trying to post pictures of my tools of choice to break tabs but cannot get this system to load a picture. I will try to send links below. Thanks again.

https://photos.app.goo.gl/gpspcqEsmT7unvZb6

https://photos.app.goo.gl/gD9AiNQeQZUNNrap9

Video of finger over the hole in the cap.
https://photos.app.goo.gl/GD9JLr8RiVVWaaFj8