2001 Kia Optima 2001 Kia Optima 1 coil fires and one doesnt

Try replacing with another new coil. The replacement could be bad?

Do you have a check engine light showing or codes stored?

Camshaft Position (CMP) Sensor
CMP sensor detects No. 1 piston at TDC of compression stroke. ECM uses input for fuel and ignition control. On Optima (2.5L), sensor is located rear of right cylinder head. All others are located rear of head.

Crankshaft Position (CKP) Sensor
CKP sensor detects crankshaft angle. ECM uses input to determine engine speed, misfire detection, and for fuel and ignition control. On Optima and Rio sensor located near rear of engine. Sephia and Spectra in bell housing. Sportage is located on left side of transaxle or transmission flywheel housing.

DISTRIBUTORLESS IGNITION SYSTEM (DIS)
DIS system consists of a Crankshaft Position (CKP) sensor, Camshaft Position (CMP) sensor and 2 coils. CKP sensor is located on transaxle/transmission case near flywheel. CMP sensor is located in rear of head. On 4 cylinder engines coils are located directly on top of No. 2 and No. 4 spark plugs. On V6 coil pack is mounted on rear of cylinder head. Each coil is connected to companion cylinder spark plug by plug wire. System uses waste spark method. Each coil fires 2 spark plugs simultaneously. Sensors signal ECM which cylinder is ready to fire. The ECM then triggers appropriate coil.