Diagnostic trouble code P0303 in your 1996 Ford Taurus tells you that cylinder No. 3 has a misfire condition. If your Taurus is running rough and the "Check Engine" light is blinking at one-second intervals, the misfire is severe enough that you may damage the catalytic converter if you continue to drive the car.
To diagnose a P0303 in your Taurus, you have to think about what would cause a lack of combustion in cylinder No. 3 -- the rear cylinder on the passenger side in the 3.0-liter engine, or the second cylinder in from the driver side in the cylinder bank closest to the firewall in the 3.4-liter engine. In order to have combustion, the cylinder has to have compression, as well as fuel, spark and air -- all in precise amounts, delivered at exactly the right time. As a troubleshooting aid, try changing parts between cylinder No. 3 and another cylinder to see if the DTC moves to the other cylinder.
