Hello everyone, I noticed that the engine on my 2009 Subaru Impreza 1.5 with the naturally aspirated EL15 eingine is having a rough time with idling.

The revs are all over the place. I additionally got the code before that my O2 sensor was bad so I replaced it which fixed the issue momentarily. But then the code P0134 came up and has kept comming up more often as I drove the car for the past 30 kilometers (about 18 miles).

Then I noticed a sweet smell comming from the exhaust while the engine was having a rough time idling and I am worried for dear life that the engine might be at its limit. I saw no chocolate milk on the radiator cap.

Another thing I noticed is that when I do some heavy acceleration (from 25 mph to 60 mph) that the engine sort of cuts on power between 3500 and 4000 rpm and then after 4 000 rpm goes like nothing happened. 

I am confused and worried that my car's engine might be at its limit. Please help.