Hello,
I have a 2015 Subaru Legacy Premium 2.5l with around 95k miles. Recently, at a cold start, if I put it in reverse, the engine bogs down and periodically dies. Once the motor is warm, this issue goes away, and if I garage park and it's not a cold night it also isn't an issue (basically any temp below 50 degrees it's an issue). I've had the dealership look at it and was told the transmission was fine. They recommended a "throttle Body Service" to help clean the intake and throttle body, which I did. This did not fix the issue, so I replaced the PCV with the hypothesis that if stuck, it would potentially create crank pressure issues and kill the motor. That also didn't help, and I've been considering replacing the 'idle air control valve', however, it's like $300 and I'm hesitant to dig into it if that's not the source of the problem.
Again this only happens at cold start, and goes away once the motor/tranny are fully warmed up.
Any guidance would be greatly appreciated!!
The car should be scanned for codes and the live data analyzed before any work is done. Dealerships don't necessarily have the best mechanics or service, just higher prices. Have a local, reputable mechanic check it out. Don't go replacing any sensors unless they test bad. You need to get a proper diagnosis before you consider replacing anything.
I've been considering replacing the 'idle air control valve',
Searching parts.subaru.com it appears that the 2015 Legacy does not have an idle air control valve. The last model year that comes up for is 2014. (Of course it's possible an early production 2015 model might still have it. You'd need to plug your VIN into that site to be certain.)
You might try cleaning your MAF. Also check low-hanging fruit such as filters and spark plugs. Beyond that it would be helpful to scan for any codes, and also take a look at live data when the problem occurs.
Also stay away from dealers for anything other than warranty or recall repairs. (Avoid chain shops as well.) A good local mechanic that will actually do some diagnosis rather than guessing or throwing parts at a problem is your best bet.
