Engine Problem??

I have a 93 Toyota Camry with a V-6 3VZ-FE Engine. In the past month when my car is fully warmed up it idles really low, like 400-450 RPM'S. It never stalls, but the whole car vibrates and it is very aggrevating. Someone told me to replace and clean the PCV valve, and the IAC valve. I replaced the PCV, and cleaned the IAC valve. And nothing changed it still idles low. What is responsible for the idle on fuel injected cars?? what could be causing this?? Thanks.

Check for vacuum leaks, clean the EGR valve, check for good spark - plugs, distributor cap & rotors, wires, check the cooling temperature sensor, check o2 sensors for responciveness, check the IAC one more time, check ignition timing (stock is 10*btdc, bridge E1 & TE1 in the diagnostic port).







The idle is controlled by the ECM. It finds the mass of the incomming airflow by the AFM's flap & IAT (temperature). Then it decides how much fuel to spray. It also adjusts ignition timing in an attempt to smoothe the idle.