Q: hey Jay. I have a vw jetta 2011 4 cyl. my car has 60,000 miles was driving and felt a slight hesitation when accelerating uphill.

Diagnostic Trouble Code P0303 means that Cylinder No. 3 is misfiring but the causes of that misfiring can be very varied. The other Code that you probably saw, namely P0304, just refers to the same misfiring but it is occurring in a different cylinder, namely cylinder No. 4. Among the causes of cylinder misfiring are faulty spark plugs, low compression, damage or excessive wear of spark plug wires and/or coils, faulty fuel injector, clogged EGR valves or tubes, burned valves, improper ignition timing, vacuum leaks, leaking head gasket, faulty camshaft sensor, faulty crankshaft sensor, faulty mass air flow sensor, faulty oxygen sensor, faulty throttle position sensor, faulty catalytic converter, and others. If you want the cause pinpointed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a misfiring diagnostic and the responding certified mechanic will get this diagnosed and resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic.