Hi, all. I just recently picked up an '06 Outback 2.5 (non-XT) and have been working on getting it back on the road. It hasn't sat long at all, couple months at most before I bought it. Previous owner parked it after it wouldn't pass CA smog due to a check engine light, turns out it was a bad oil pressure switch on the passenger side VVT solenoid. Got that replaced, no CEL now, however the engine isn't running quite right.
At idle, if I give it gas, it hesitates and shakes some like it's about to stall for maybe a half second before it picks up. When driving, I'll feel the engine shaking/vibrating when accelerating even modestly just about through the entire RPM range. If I let off, the shaking stops immediately, same if I pop it in neutral. It seems to be idling fine around 750-800rpm. There's a bit of blue smoke on start up after it's been sitting overnight, not a lot but a small puff.
So far, I've replaced the air filter, cleaned the back side of the throttle body (facing the firewall), cleaned the MAF sensor and put a bottle of fuel system cleaner in the tank. I went through and cleaned my battery connections, ground points that I could find, and MAF sensor. No oil on the plug leads or plug bodies. Plugs themselves looked good, not black or anything unusual. Nothing seemed to make any impact on the hesitation I'm experiencing. I took this short 1 minute video sitting still to show what the RPM does with different throttle input. If you roll on gentle, it picks up fine but quickly pressing the gas makes it shudder and bog some before it catches up. You can definitely hear the shudder and see it by the shadow on the middle of the wheel.