1. Perform the spark test and identify the malfunctioning cylinder. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [LF].)
2. Replace the ignition coil of the malfunctioning cylinder with that of a normal cylinder, and reperform the spark test. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [LF].)
If the spark is not normal due to a malfunctioning ignition coil, replace that ignition coil.
It is unlikely that all four ignition coils fail to operate properly. To prevent replacing a normal component, perform the above procedure, identify the malfunctioning ignition coil, and replace it.