When your 2017 Honda Accord displays the P0304 code, the powertrain control module has identified consistent misfires in cylinder 4. The 9th generation Accord offers naturally aspirated four-cylinder and V6 options.
2017 Accord Engine Options
The 2017 Accord offers the 2.4L i-VTEC four-cylinder (185 hp) or 3.5L V6 (278 hp). On the inline-4, cylinder 4 is the rearmost. On the V6, cylinder 4 is on the rear bank.
Typical Causes
- Ignition Coil Degradation: Age-related failures common
- Spark Plug Wear: May be at or past service interval
- Fuel Injector Issues: Deposits from years of operation
- Vacuum Leaks: Gasket and hose deterioration
- Valve Adjustment: 2.4L may need valve clearance check
Diagnostic Process
Use Honda diagnostics for detailed access. At this age, systematic testing is important. Monitor misfire counts. Test ignition components. The 2.4L uses port injection avoiding carbon concerns.
Repair Recommendations
Replace ignition coils and spark plugs if not recently done. Clean fuel injectors as needed. The 2.4L may benefit from valve adjustment. Repair vacuum leaks.