P3654moderate severityPowertrain
GDI Carbon Buildup Detected - Intake Valve Performance
on 2021 Mazda Mazda3 2.0L I4 · FWD
What this code means
The PCM has detected a pattern consistent with carbon buildup on the intake valves. GDI engines are prone to intake valve deposits since fuel does not wash over the valves.
Symptoms
- Rough idle that worsens over time
- Misfires at cold start
- Reduced power
- Poor fuel economy
- Engine vibration
- Cold start stumble
Common causes
- Normal carbon accumulation from PCV gases
- Excessive short-trip driving
- Oil consumption past valve seals
- Low-quality fuel
- Lack of intake valve cleaning maintenance
Diagnostic steps
- Perform relative compression test
- Monitor long-term fuel trims per cylinder
- Inspect intake valves with borescope
- Check PCV system operation
- Review driving habits and mileage
Repair notes
Perform intake valve walnut shell blasting or chemical cleaning. Install oil catch can to reduce future buildup. Consider intake valve cleaning every 60,000 miles on GDI engines.
Other Powertrain codes on this vehicle
P0001
Fuel Volume Regulator Control Circuit/Open
P0002
Fuel Volume Regulator Control Circuit Range/Performance
P0003
Fuel Volume Regulator Control Circuit Low
P0004
Fuel Volume Regulator Control Circuit High
P0010
Intake Camshaft Position Actuator Circuit/Open Bank 1
P0011
Intake Camshaft Position Timing Over-Advanced Bank 1
P0012
Intake Camshaft Position Timing Over-Retarded Bank 1
P0013
Exhaust Camshaft Position Actuator Circuit/Open Bank 1
P0014
Exhaust Camshaft Position Timing Over-Advanced Bank 1
P0015
Exhaust Camshaft Position Timing Over-Retarded Bank 1