IAC SYSTEM RPM LOW
PCM controls idle speed with an Idle Air Control (IAC) valve
to a calculated RPM based on sensor inputs and actual engine RPM. PCM
moves IAC valve in or out to vary amount of airflow into intake
manifold and thus decrease or increase idle RPM.
PCM commands IAC in counts. A higher count, allows more air
to by-pass throttle plate (higher idle).
You may notice a lower idle and possibly rougher idle.
- Vacuum leak
- Restriction in the intake or exhaust
- A faulty positive crankcase ventilation (PCV) valve
- Dirty throttle body