First of all sorry for my poor English, I live in Kuwait and I'm not native speaker.
I got my Legacy 2 years ago and it had 80,000KM (~50,000 miles), it is perfect car and I didn't had any problems until today (I add another 50,000 miles in two years and millage is 100K miles now). All I did in this two years was only oil change and other regular services in local dealership everything on time.
Every 3-5 months I was getting engine light on with traction control light on and blinking cruise control light. When I take it to dealership every time they just reset ECU and lights was off for next 3-5 months and they say this is just oxygen sensor error and not a big deal.
Today I get extra money and change all things dealership recommend me to change in last two months. This is parts they changed today:
Front Shock mounts;
Also I did following services:
Engine flush with FORTE;
Fuel system cleaning;
In addition I decide to move to synthetic oil from mineral and I tell them to change oil to Mobil 1 5W-30 instead of mineral oil they were using before (not sure if good decision). They flush engine first and after this they put new synthetic oil with new OEM oil filter.
After all this changes when I finally get my car back and I was excited to test it on highway problem start
Before I was heading to highway and driving slowly (20-25 mph), everything was fine but when I go to highway and press gas pedal with full power only thing what happened was sound like fart from exhaust system and car continue driving slowly. Only after 3-5 seconds it start increasing speed but very slowly. I try it few times and I get same results all time.
If I increase throttle slowly everything is okay but if I press gas pedal suddenly with full power this is what happening
problem is exactly same if car is in parking mode, if I press gas slowly and increase power step by step RPM meter works fine and going up to 5 but if I press gas pedal full power when engine is idle RPM will stack at 1 for few seconds and only after 2-3 seconds it will start increasing.
BTW I didn't get engine light on
also before this service everything was fine and I never had same problem before.
I bring my car back to dealership and they told me exhaust system needs to be cleaned and they told me I have to replace catalyst controller
also they told me they can just remove catalyst and drive cat-less but at my own risk (in Kuwait there is no any emission control and driving without catalyst is legal).
I agreed to removing catalyst but now I read too many opinions online about catalyst removal and as I get it it will reduce torque and also may cause engine damage because oxygen sensors will go crazy and ECU will be messed up
Problem is I can't trust local dealership because they didn't have much experience. Subaru is not popular car here, every month only 20-25 new Subaru is sold in all country and you can't find any mechanic outside dealership who knows anything about Subaru. This is main reason why I registered on this forum. I read too many topics here and this is only competent forum about Legacy so far.
Tomorrow morning I'm going to cancel catalyst removal and ask them to just cleaning exhaust system. On this forum I read posts about similar cases and I find out this problem may caused by knock or oxygen sensors but dealership doesn't say anything about it
My car is non-turbo 3.0H6 Legacy with 5 speed automatic transmission. I'm not sure if there was same engines available in USA for this year but as I know there is 2005 Outbacks with same engine in your country.
Thank you in advance for your help