[Sakian2]

Hello guys, new member here. I bought a forester 2012 x limited at 138000m. I noticed it lose power after running for a while and it get very slow. For getting the power i have to press gas more than 70% and it shifts the gear to 3rd and get the boost. I found the transmission oil is not in a good shape and its brown. I have changed the spark plugs, cleaned the throttle and cleaned the egr. I also reset the throttle. The car is more responsive but it slown down after running for a while.No check engine or engine codes. Can anyone suggest me something why? Also should i change the transmission fluid as i dont know it had been changed before or not?

 

[Mr.AC]

Sounds like a fuel pump blockage/clogged. Could be some crappy gas used or some lose dirt that clogs up the strainer/pick up line. Or could be the fuel pump losing power.
Second option: could be spark related, either the coil pack or some bad connection. But usually those would give off a check engine light.

One thing you can do is do a compression test. Hopefully it would tell you if you have a major problem or not. If its not blowing smoke after you run it or oil in the coolant, could be piston rings or the valves.

If you don't know how long its been since the last tranny change, might be time for one.