Did you drop the sump and clean the pipe from the pcv canister? I had an XC70 do the same thing.

https://www.matthewsvolvosite.com/forums/viewtopic.php?t=53246

Yeah, I just replaced the entire PCV system, and dropped the pan and cleaned out the lower internal pcv ports in the engine. Unless I hooked something up wrong, or broke something in the process, there's no suction.

At idle, the rubber glove trick is producing more positive pressure than it did before I changed the system. The engine runs so rough right now, I cannot test the engine at speed, I run and turn it off it backfires so bad. Before, at idle, it was neutral. Not- some positive. Certainly no negative. I'm going to dig into some stuff this weekend, and redo the compression check, but I'm scared of ring blowby. The head- I'm hoping is okay, having a valve job 60k ago.

If the compression is that bad you only need your thumb over the hole...

:) I'm going to ease into this. Just spent 8+ hrs wrenching on this sucker and I get the privilege of sorting though it again.

The scuffs all over my hands/arms haven't healed yet from last weekend. Arghh!!!!!

If it's that bad, pulling the spark plug wire off will make zero difference to how the engine runs.

And a laser temp sensor will tell you if a cylinder is firing or not.

Check to see if your exhaust has any flow through it.

Cleaned the banjo bolt into the manifold?

:) The old banjo bolt one way valve was jammed and the round metal pcv attachment piece the banjo bolt goes through (and has the copper washers on each side), was clogged 100% with carbon and the plastic tube from it to the crossover pipe was broken. I don't know if the plastic tube was pre-broke, or if I snapped it during removal, but it was trashed. The access on that is a proper *****, so I loosened the manifold, and yanked the entire assembly (manifold and all) up so I could access that mother effin' banjo bolt from hell. That might have snapped the plastic line from the banjo to the x-over.

Somehow I must have clicked on 4 banjo bolts for the order, because I have 4 new ones. :) I did use the nicest looking one.


Today, I went and did something that needed to be done to cross off the checklist, but not necessarily something that makes sense from a pcv or low compression concern.

Earlier, I was getting a fuel trim bank malfunction, that can mean a lot of things, so I replaced the upper 02 sensor.

The car runs ****ty, but a lot less ****ty than it did. Before, it was backfiring so bad through the intake, I just had to turn it off. Now, it runs like it's missing on a cylinder. Still crappy, and struggling, but it runs well enough to get the feel it's missing.

I know the feeling. It feels like it is running on 4 out of 5 cylinders.

No code though. Tomorrow- I'm checking timing marks, compression, and ignition and fuel injection. I do have new plugs, new injectors, new fuel pressure regulator, new fuel pump, new fuel filter, and I rewired the injectors due to a fire several years ago. I need to recheck the wiring to make sure I don't have a dead injector.

Clearly, I'd like to get a vida on this, but, with the fire damaged wires (now replaced), and the older pcv system (now replaced), there were things I needed to go through before a dealer code read would reveal anything worthwhile. They would just laugh me out of the building. They quoted something like $500 for the o2 sensor, so I was just like "let me spend $100 or so for the part, slap it on, and make one less thing worry about. I've got the lower 02 sensor too, and will put that on (just because) after doing all the other stuff. I'm in a parts throwing mode, but I think, getting to the end of that, and they were things that can't hurt to replace anyway. The misfire gives me hope.

ok. thanks. dumb question, do you point it at the exhaust manifold? block?

today, the car was running good enough to warm it up- well, not good at all, but it wanted to run, not blow up like last week. God, that was painful. There was moisture/water vapor coming through the exhaust. Seemed normal, but I did not try to quantify it.
Also, when I replaced the upper o2 sensor, no oil in the exhaust downstream of the turbo. it was whitish greyish smokey dry like the exhaust fins on a turbo.
I'm hoping no clogged cat at this point.

Are the intercooler pipes all connected ok? Intake pipe to the turbo? All the one way valves ok? Just sounds like maybe a big vac leak somewhere.

Block, or exhaust very close to the block.

Thanks. My laser thermometer is mia at the moment. I put it somewhere I wouldn't misplace it. I did get out though and tinkered (very cold outside).

Compression with a HF gauge- 120 across the board. 180 with an ounce or two of oil. Hmmm....

Compression isn't your main problem. I think at 120 dry it should run better than what you're experiencing.

The good news, it's not a major engine issue. The bad news, it's something else....cat maybe? I don't think it's PCV...massive vacuum leak?

That's what I'm thinking. I'm going to hunt down the laser temp sensor and make sure everything is firing.

Clogged cat, failing ecu, bad injector rewire short, or failing coil are all on my suspect list. Dang thing still not throwing codes!

Oh well 120 is much better than I was expecting.

I'm going to throw on the downstream O2 sensor, not that I expect much. I was surprised what a difference the upstream made.

Problem is, it's cold as heck outside. Not fun to work in.:D

Unplug injectors or spark plugs one by one.....you might have a dead cylinder from spark or fuel. But from what you've described it's likely bigger.

Even on four cylinders it should run.

Oh... on your suggestion of vacuum leaks- never underestimate the impact of a loose intake manifold :D

There's that pia manifold bolt crammed inbetween the manifold and the t-stat. Now, I would never leave that loose, but if I did, that might make a difference. I also cleaned any electrical connection I messed with.

Car now starts and idles cold normal. Still some missing on warm idle low RPM, but, it runs and has negative pressure in the case.

I'm still going to check injectors and spark plugs as you mentioned. Slow steps getting better.

The low idle mis was the reason I went down this rabbit hole. Now with the new pcv system, and all the other stuff, I can figure it out.

Also, never lose an intake manifold bolt. Those fuch ers are 7mm, and impossible to find...

Truth^

Okay- I replaced the downstream O2 sensor- also, went to HF and bought a metric crowsfoot to tighten the pia bolt the last bit.

viola.

success. Smooth idle both cold and warm low rpm.

I dropped the crowsfoot into some dastardly crevice, went fishing with a magnet, and came up with a 10mm socket that went missing in 2018. The crowsfoot is still in there. I will go fishing again tomorrow.

Only weird thing is the right side of my instrument cluster went dead. No fuel tank level. No CEL. I'll deal with that later.

Thanks everyone for input/ help.

Great work, Leaky!