My car for the passed few months has been having a rough cold start.

Hi, this is Bo, an auto expert on RepairPal's Car Genius team! What you’re describing sounds like your BMW is having a little identity crisis every morning—starts strong, then nearly stalls, then overcompensates. Classic symptoms of a cold start air/fuel imbalance, and on a 2015 535i xDrive, there are a few usual suspects. First, check for vacuum leaks—a cracked intake boot, leaky PCV valve, or even a loose clamp can throw off the air-fuel mix just enough to cause rough cold starts. Next up: the mass airflow sensor (MAF) or intake air temperature sensor could be dirty or failing, sending bad data to the ECU. Also, don’t rule out carbon buildup on the intake valves—direct-injected engines like yours are prone to it, and it can mess with airflow at startup. If it’s never been cleaned, it might be time for a walnut blasting. A scan tool that reads live data during cold start can help pinpoint if it’s fuel trims, misfires, or sensor readings that are out of whack. If you need any further advice or want help finding a trusted RepairPal shop in your area, please feel free to call us at 877-913-1554.