Hello all, I own a 99 v70 glt with 152000 miles. The car has a "stumbling" idle, with what looks excessive white exhaust( hard to tell though as cold as it is outside). It goes from 800 to 1000 rpms, fluctuating quickly in sync with the exhaust blowing more at 1000 and less at 800-reminds me of blowing smoke rings. I changed the spark plugs 1000 miles ago, and when i pulled the plastic cover off there was about a 1/4 inch of oil on top of the motor.-along with the spark plugs I also replaced the fuel filter and thermostat, and also gave the car a seafoam cleaning. After the seafoam, the car smoked a little less than i expected, but since then has smoked more than before. I pulled the codes today and read PO442 Evap emission system leak(small leak) and PO422 Main catalyst efficiency below threshhold (bank 1) The car is not lacking power, but mpg has dropped about 1 mile in the past 2 months, and it needs an inspection in 1 month. Any ideas where to start? I matched some symptoms with a few other posts that lead to replacing the pcv components, or cleaning the throttle body. Any advice is appreciated. I priced the parts for the pcv, any ideas what it would cost to have them replaced? I don't think i have the time to do it myself right now.
Thank you

 

The oil on top of engine is sign of constricted PCV; at that mileage it's over-due for it if it's never been done. Clean the throttle body while at it too.

Don't know if that's causing your idle issue though; could be, or not.

I would be curious to know what your oil consumption is? Also are you losing coolant? I.e. could that be what's going out the exhaust? Compression test might be telling as well.