2001 Volvo T5 S60 Idles Roughly, hesitates at idle

[carboncow]

Agreed on disconnect MAF and see
Also could be VVT solenoid (been there) so disconnecting that can show improvements. I had hesitation at speed and weird idles
Before you waste a penny on an ETM find someone with a Vida Dice (indie or stealer or member) and do an ETM sweep. Everyone told me my ETM was bad (2nd one) and it passed the test with flying colors. Thus went direction of VVT per recommendation that was spot on

This all assumes you have no leaks. I had turbo pressure sensor (or was it air temp sensor?) pop off the tube from the intercooler to the intake and it caused big idle issues.

[SuperHerman]

I suspect your ETM is dirty or worn out if it is a Marelli unit. The suggestion to have an ETM sweep performed is very good advice. But if you are in the least bit handy and willing to part with $135.00 a rebuild to Contactless plus deep cleaning will not hurt either way as going to the dealer will cost you $135 to have it checked out, assuming you don't have access to VIDA.

First go through the other suggestions as they only cost you your time, if they are not fruitful then approach the ETM.

[T5S60]

Replace your oil cap seal. It's not spilled oil; the oil seeps slowly from under the seal and into the channels which lead into the spark plug wells.

Usually a 99c part from FCP or IPD.

You guys have any advice on the best way to get the spilt/leaked oil out of the spark plug compartment? Just use paper towels/something absorbent? Or would a shop vac work.

[sergio]

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abscate, I am very curious to know how (from which point on the line) the unfiltered air would be entering the manifold? Mine is a 02 turbo and I don't see any hole /intake where unfiltered air could get in there.
As you know I am having a different problem with my engine and very tempted to pull the MAF sensor for a while.

Usually you disconnect the plug on the MAF and see if the car runs ok. With no MAF the Engine control system defaults to a look up table of fuel delivery based on rpm and will run pretty well, but with lower mpg.
Removing the MAF is a bad idea as it would open the intake manifold to unfiltered air.

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[abscate]

If you just pull the MAF out it is in between the air filter and the intake, so that will let dirty air in.

Just pull the plug on the MAF and see if your car runs better, you do not need to actually remove the MAF.