I'm in the process of changing my timing and serpentine belt and when I took off the sparkplug cover, I saw oil sitting in the area around the sparkplug. I researched it and said it could be either the PCV system or a bad head gasket. I recorded a video of the weird sound my engine was making before starting the timing job (ill attach the link) and I'm relatively new to Volvos and working on cars in general, so I don't know if the sound is making and the shaking of the engine is the PCV or the head gasket. any help is appreciated!
video:

 

That's not good. The sound might be something (like a head gasket) acting as a reed. Could certainly be a different (and cheaper to fix) gasket. The car has sheetmetal gaskets at intake and exhaust ports, so there are a bunch of them that might squeak. Could be something else entirely.

Personally I would never let oil on top of the engine be an indication of anything other than crankcase ventilation. They are gonna get oil up there in 25 years time. But you do have some symptoms of something else going on there.

 

The most common cause of oil in the webbing on top of the head is the oil cap seal.

Your weird noise sounds like something is rubbing, with the spinning belts - I would find that as quickly as possible. Or is that the sound of the power steering pump? Check the level is it all foam? If so it will be very noisy until you get the foam out - that can take up to an hour - and can be a very frustrating process, but have done it many times for customers. Post back if it is all foam/noisy and you can't get the foam out - I can suggest a method that works.

The rough idle - the fuel mixture could be way off - any codes stored? Could be an intake air leak, something unplugged or possibly a bad air mass meter - but don't replace that first, diagnose the problem, start with a stage 0 tune, and eliminate all the other possibilities. It's not the pcv or a head gasket.

 

I'll check the oil cap seal too, I'm almost done changing the belts, water pump, and idler pulleys so ill see if that makes any difference, but I'll also check the power steering pump. I'm gonna take it to a mechanic too, to see all the issues and try to just get everything done

 

Let us know what you find. Sounds like idler pulley and/or water pump is about the let go. Maybe a big vacuum leak too?

 

my vote is the oil fill cap, particularly if your car fails the rubber glove test for positive PCV pressure.