2002 Silverado P0300 Code: Cold Weather Rough Idle and Engine Stalling
My 2002 Chevrolet Silverado has been exhibiting a recurring issue when the outside temperature is cold. The service engine light activates intermittently, and when it does, the truck runs roughly at idle—sometimes even stalling completely. This behavior only occurs in cold weather and typically resolves once the engine warms up. The check engine light doesn't stay on consistently; it may flash for 30 seconds, remain lit for 15 minutes, or persist until I turn off and restart the vehicle. A previous scan revealed P0300 (Random/Multiple Cylinder Misfire) and P0171 (System Too Lean). I recently replaced the Mass Airflow Sensor (MAS), but the problem persists. The issue seems to be cold-weather related, and I'm seeking advice on how to diagnose and resolve this. Any insights or suggestions would be greatly appreciated.
A vacuum leak on Bank 1 (driver's side) is a common cause of P0300 in cold conditions. Inspect all intake manifold vacuum lines and connections, especially when the engine is cold. Look for cracks, loose fittings, or disconnected hoses. A vacuum leak can disrupt air-fuel mixture sensing and trigger misfires. Addressing this could resolve both the rough idle and intermittent stalling. Good luck—please update if you find a solution.