10/12/2026
This Acura TSX was running very rough.
The scan showed a cylinder 4 misfire plus P0420.
The important part was deciding what to test first.
The technician moved the ignition coil from cylinder 4 to cylinder 1.
The misfire moved with the coil.
That gave us a clear direction.
The ignition problem was repaired first instead of assuming P0420 automatically meant the catalytic converter needed replacement.
That is why a scan code is only the beginning.
Testing tells you what the vehicle actually needs.
Read the full article:
Acura TSX Running Rough with P0420: Why We Fixed the Misfire First
https://autorepairshoreline.com/2026/10/acura-tsx-p0420-misfire-diagnosis/