DTC P0303 - Cylinder No. 3 Misfire Detected: Condition

WARNING: This page is about a different car, the 1997 Mazda Millenia. However, it is still accessible from the selected car via links, so may be relevant.

DTC is set when ECM input signal from Crankshaft Position (CKP) sensor signal is irregular. Possible causes are:

Ignition system malfunction on cylinder No. 3.
Low fuel level.
Low battery voltage.
Fuel system malfunction.
Insufficient compression on cylinder No. 3.
Incorrect CKP sensor air gap.
EGR system malfunction.