I have a 2005 Subaru outback 2.5L no turbo.
For a few months, the car has been stalling at least once a day usually withing 15 minutes of driving although the car is at running temperature when it happens. For most of the time, the car does not stall nor run choppily. No rough idle. No lights/codes. The idle is low. When stopping the idle usually dips to ~500rpm but this does not always mean the car is going to do its stalling for as I mentioned it usually only stalls once and sometimes twice in a single day and my one way commute is over 30 miles with many stops.
I have taken it to two shops. The first shop changed the coils. After that failed to fix the problem I replaced the air filter, cleaned the throttle body, egr, maf all to no avail. I did my best to check for air leaks with a water bottle spraying and listening for a rough idle upon intaking the water. Reading online I looked for the idle air control valve but did not find one and assumed it was part of the throttle body. I pulled the battery for a while, the cells cleared and I put it back on hoping the ecm would relearn. Nothing worked.
I then took it to a subaru dealer service center. They successfully reproduced the issue but could come up with nothing after saying all sensors were reading fine, but wanted to start trying stuff like a "fuel system cleaning and relearn" >$350. I decided to take the car back because I was confident this would not be an effective route but would begin to add up with no results.
I bought a used throttle body and swapped it out. As a last ditch effort I followed "subaru idle relearn" twice but this also failed.
I'm at a complete loss now. Some have suggested it's the torque converter.
What should I do with this car with ~170k miles?