2002 S60 Rough idle but smooth at higher RPM

[quietcoolone]

Can you remove the intake end of hose coming from pcv and see if pressure at dip stick goes away?

I can certainly do that, but can't now because its intermittent or has a mind of its own.
Earlier today i started her up in hopes of duplicating the issue but she ran perfectly (no noise, no pressure, no rising fuel trims).
Went on a 10 mile ride while monitoring FT etc and except for the CEL the engine ran good.
I will start her up tomorrow morning and post results (this seem to happen on cold engine starts)
BTW, what should happen when i remove that hose?

Thank you.

[draser]

I hope you'll see a stream of gasses come out and less/no pressure at dipstick. Are you sure PCV canister does not have loose crud in there?

[quietcoolone]

I hope you'll see a stream of gasses come out and less/no pressure at dipstick. Are you sure PCV canister does not have loose crud in there?

Started her up this morning and immediately saw STFT trending high (24.2) vacuum leak?
Attempted to remove the small elbow hose that connects the breather box to intake (as per draser) but it was impossible due to its location (i would have to remove the thermostat housing in order to make room.)
Pulled the dipstick and released the pressure:(correction, i meant vacuum)
Engine coughed a little (as if it was gasping for air/fuel),
few seconds later the idle was smooth and FT started trending down (-2.3)

i can assure you that if i was to start the car again it will run just fine (not lean), but for some reason if left overnight or for an extended period of time it will start-up and go lean (High FT) and for now the only way to get FT down is by opening the fuel cap and/or dipstick or by OT - release pedal.
I can't be 100% sure of whats in the sealed canister, but i can tell you that i added water, shook it up and drained it like 3 times, then hooked up my air compressor and blew air through it, let it drain overnight before installing--- i'm confident its not clogged.

Just wanted to add that i started the car again this afternoon (10 hours later) and it was a repeat of the aforementioned situation-- except this time i opened the oil filler cap (lots of vacuum)

Adding to this post:
This morning i discovered that what i have been calling pressure is actually vacuum (see my corrections above).
I decided to start the car with a rubber glove over the oil fill hole ( i expected it to inflate),however it was sucked in (see picture). At that point i took it out and put the cap back on and instead put a vacuum gauge in the dip stick . Found out that the engine was actually sucking air (no wonder i was having a hard time releasing the gas cap). The vacuum amount can be seen in the picture below. (10 inHG or 4.9 psi)
I also took a picture of the scanner so you can see some parameters.
Put dipstick back on and soon after the FT went to -3.9 for ST, and 3.9 for LT.
I'm sorry for misrepresenting the events but i do have it right this time. (Vacuum not pressure)
Does this change anything?

[precopster]

Is that 10psi of vacuum? That's a lot of vacuum if it is.
Could the intake system have breached into the crankcase somehow?

[quietcoolone]

Is that 10psi of vacuum? That's a lot of vacuum if it is.
Could the intake system have breached into the crankcase somehow?

10 inHG or 4.9 psi

[draser]

Isn't there some sort of valving in the pcv where it only opens into the intake after a certain crankcase pressure is reached? If you have too much vac now it does the reverse of blowing seals, it sucks air at seals. Mike, any idea?

[quietcoolone]

Isn't there some sort of valving in the pcv where it only opens into the intake after a certain crankcase pressure is reached? If you have too much vac now it does the reverse of blowing seals, it sucks air at seals. Mike, any idea?

Found this on another site:

The non-turbo should be right around atmospheric pressure at idle. If it has enough negative pressure at idle that you get a suctioning sound through the dipstick tube when you pull out the stick, or you hear a squealing noise from down low in the engine when the dipstick is in place, you have a bad check valve in your oil trap. There is no way to clean them. Replacing the PCV breather box is the only remedy.
There is a spring loaded valve that regulates crankcase pressure in the non-turbo cars. This valve can stick. When it does, full manifold vacuum is present in the crankcase. It can make a howling/squealing sound at idle depending on how bad it is. The sound is air actually being pulled past the crankshaft seals into the engine. Needless to say that's not good for the seals!

i had not idea there was a check valve inside that breather box--- if this is true then this could be the issue-- anyone?

[draser]

Exactly, see my prev post. The flow of blow by gases into intake is metered.

[quietcoolone]

If you have been following this thread, you know i had already "cleaned" the oil trap box and hoses. Unfortunately that was not enough because the oil trap has a regulator inside that can't be cleaned. I cut it open for you to see what i found inside. This section of the trap connects to the intake manifold which explains the vacuum issue.
To fix this you must replace the oil trap.
Over the weekend i replace the oil trap box and manifold gasket with new ones from Volvo and i can finally say: No more high vacuum at dip stick and oil fill hole.

trap.jpg (60.59 KiB) Viewed 1738 times

sludge.jpg (40.55 KiB) Viewed 1738 times

I also resolve the P0420 code by adding a 1M ohm resistor in line with the O2 sensor signal wire (blue) and a 4.7mf capacitor between the blue and white wires.
The front 02 sensor on this car is a wideband A/F sensor who's waveform is anything like the rear sensor.

osb1.jpg (69.33 KiB) Viewed 1738 times

the front AF/Sensor is based on current not voltage and the rear sensor waveform oscillated between 0 and .9V which cause the computer to throw the P0420 code. After the modification the Rear O2 sensor voltage stayed around 0.5V

o2s2.jpg (72.71 KiB) Viewed 1738 times

Engine fuel trims are well within 10% and runs smooth.

ft.jpg (75.84 KiB) Viewed 1738 times

I would like to give thanks to draser for pointing me in the right direction and going the extra mile by providing waveforms and readouts from his personal vehicle for comparison --- Thank you!!

[precopster]

I always thought it was the 2003 and 2004 that had the fandangled oil trap. Also I wasn't aware it was in any way connected to intake vacuum.

Great work draser and to you quietcoolone for persistence in this matter.