The P1078 code in your 2021 Honda Passport indicates the Intake Manifold Runner Control (IMRC) is stuck in the closed position. This Honda-specific code signals the variable intake system cannot open for optimal high-RPM airflow.
IMRC Stuck Closed Effects
When the IMRC remains closed, the engine operates with long intake runners permanently. This provides good low-RPM torque but restricts airflow at high RPM, limiting top-end power.
Common Causes of P1078
- IMRC actuator motor failure
- Jammed butterfly valves
- Binding linkage
- Carbon buildup locking valves
- Electrical circuit failure
- Broken vacuum lines (if vacuum operated)
Symptoms of IMRC Stuck Closed
- Check engine light on
- Reduced high-RPM power
- Engine feels restricted at high speed
- Poor highway acceleration
- Possible engine knock from restriction
- Fuel economy may suffer at highway speeds
Passport V6 Performance
The Passport's V6 relies on the IMRC system for its blend of efficiency and power. Stuck closed reduces the engine's ability to breathe at higher RPM.