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High idle at operating temperature with PO505 Fault code thoughts
Hello.
I have a 2001 Toyota Yaris 1.3 auto that has today developed a PO505 fault coded (idle control system malfunction) since cleaning the throttle body and the IAC valve.
This PO505 code is in history, current and pending.
History
I removed the throttle body with idle air control unit attached and cleaned them both off the vehicle. The IAC motor was removed from the IAC unit and the IAC rotary valve was sprayed with carb cleaner. The rotary valve was rotating fully very freely.
Upon reinstallation, both rubber O rings were correctly in place and the rotary valve was positioned into the recess of the IAC motor. The rubber seal between the intake and the throttle body was in perfect condition.
After reinstallation high idle
When the vehicle was at operating temperature in park or neutral the idle was very high at 1700 rpm! After a few hundred miles the idle came down to 1400 rpm and is now at 1100 rpm (occasionally seeing between 800 and 900 rpm, but this is after over 500 miles of driving). If the engine is idling in “drive”, the rpm is around 700 to 800 rpm.
I have noticed that cold idle has got worse during this time. Upon cold start up the engine flares up and then drops to between 600 and 700 rpm on a cold start. Once at operating temperature the idle goes up to 1100 rpm as above.
Data
Cold start duty cycle is 52% and at operating temperature at idle the IAC duty cycle is 25% with no accessories switched on. This number does go up to between 37% and 45% when the throttle is blipped or when the AC is switched on. The IAC is definitely flaring upon start up. Absolute throttle position at idle is 11.27%.
The Yaris drives perfectly other than the dodgy idle speed. Fuel trims look well within spec.
I’m thinking the idle is slowly relearning because although it is far from correct, it is slowly improving but today the check engine light has finally come on with the PO505 fault code which has thrown in a curve.
Any thoughts as to how to handle this PO505 fault code?
Thanks
Steve
Topic Author
