I have a 96 Legacy Outback Wagon 5spd 2.2 with recently rebuilt motor (25k ago). I have had problems since day one with it when it comes to acceleration. If I floor the pedal it takes maybe a 1 second to really respond. When I try going off roading up a hill I can't get it to go because of this. I have had 5 subarus and they never had this problem. My 91 legacy climbed way better than this.  I've also been getting 20 to 22 MPG which I usually get more with these cars. No check engine light. I have a donor car so I've been swapping parts. So far I have swapped Front O2 sensor, all 4 injectors, MAF sensor, New PCV valve, New Spark Plugs, pretty sure I did a fuel filter 25k ago, New wires and I've done a fuel system cleaner. What else should I do? Thanks

Try disconnecting the cat (it will be real loud) but then see if acceleration uphill is improved.

If so, the cat may be clogged and the pieces block the flow and even more so on an incline.

Edited August 13, 20178 yr by brus brother

bad knock sensor could be pulling ignition advance ?

I disconnected the cat, replaced TPS and Knock Sensor. Nothing helped.

pull the covers and check cam timing.

Did you replace the MAF with a used one or new MAF? Used MAFs suck in my experience. Did you try cleaning yours? Try a new one.

 

Next up would be a fuel pump. A walbro 255 lph would be a nice cheap upgrade.

I've had 4 90's subarus.  I must admit that I haven't had this exact problem.  I have had problems with the MAF and the knock sensor. So the question is:  did you use OEM with the MAF and the KS replacement?  It's probably something else, but tit still needs to be settled.

 

By the way, I have had no problems with used MAF or KS.  They don't fail that often so that one taken from a wreck would be likely to be defective..