Hi there. I have a 2012 Lacrosse that, other than the replacement tranny luckily under our extended warranty we normally don't do, it's been a great car. I've noticed that the engine occasionally "stumbles" when the RPM's are around 1500. If driving around 2000 RPMs or more, the stumbling isn't noticed. Also, it appears to lessen when using higher octane fuel. No dash codes. 3.6 liter. 150k miles. I cleaned the intake and MAP sensor with the appropriate cleaner. Any thoughts?
check the basic stuff, air filter, spark plugs, fuel pressure ...
No dash codes
To properly troubleshoot, use a scan tool and report back with any codes. You can't just go buy the dash lights alone. Also look at the live data such as fuel trims. Check the FAQ on Troubleshooting
Sorry. MASS flow sensor, not MAP sensor.