what is code p0303 on a 1997 saturn sl series

Code P303 is a misfire detected by the crankshaft sensor. Misfire in a cylinder could be several different possibilities. First I would check compression in the cylinder to make sure the valves are seating properly. It could be an intake leak or fuel injector problem as well.. Tests would have to be performed and data collected to pinpoint the problem.

I would like to add code P303 is for cylinder #3. At least it's not a random misfire which are hard to troubleshoot. Cylinder 3 is where your problems are, so start there.

I should collect my thoughts before I post, but the answer as to why the check engine light is blinking is because this indicates an engine malfunction which could cause more damage if continued driving the vehicle without getting the problem resolved. In a misfire condition, raw fuel could be sent down the exhaust manifold to ignite in the catalytic converter causing damage. This could make bigger problems down the line if not corrected.

sometimes if you change out spark plug and wire in cylinder that misfired situation is corrected.