Q: Engine shaking after put in gear

Hello. If you fixed a couple problems yourself I first want to commend you on that because you have to be some type of car guy to do so. I highly doubt an oil change will be the cause for your engine stumble. There’s likely another issue going on that needs attention such as a misfire. If your vehicle has a misfire it will stumble or feel as if it is shaking when the engine is running. A misfire would also trigger a check engine light code so it will be necessary to scan the computer of your Subaru and see exactly what that code is. You may have the codes scanned but not properly diagnosed at AutoZone or Advanced Auto. But if you want to have your computer scanned and your vehicle properly diagnosed then you will most likely need a technician. The technicians we have here at Yourmechanic are mobile. They will diagnose and repair your vehicle, usually on the same day of the appointment. The staff is friendly so I’m sure one wouldn’t mind showing you exactly what the problem is and what needs to be done to fix it while they’re doing the repair. You can get a cost for the diagnosis of your vehicle along with an oil change here. https://www.yourmechanic.com