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I have an 05 Elise that I had to do a number of repairs on including rebuilding the gearbox. So the car didn't run for about a year.

Once I got it back together I ended up with a P0507 code. The car would run fine but once warm, the idle would drop before returning to normal. So I cleaned the IAC. It seemed to change how the car was responding a bit. Now when driving and coming to a stop the idle is high for a bit and then drops. I alos notice some surging when holding steady RPMS while driving.

A couple of questions:

1. Does anyone know the Toyota replacement part number for the IAC?
2. Does anyone have the apropriate FSM sections to diagnose this code?
3. Any thoughts on the problem?

Thanks
 

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could this also be due to a worn throttle valve?


from the service manual:

Code:
Idle Speed Control P0506
 P0507
P0508
P0509
P0506 Idle Air Control System RPM Lower Than Expected
P0507 Idle Air Control System RPM Higher Than Expected
P0508 Idle Air Control System Circuit Low (prior '06 M.Y.)
P0509 Idle Air Control System Circuit High (prior '06 M.Y.)
Description
Prior to '06 M.Y. the ECU controls the air entering the engine with an idle air control (IAC) valve. To increase the 
idle the ECU commands the IAC to open up. This allows more air to bypass the throttle blades. To decrease 
the idle speed the ECU commands the IAC to close up. This will reduce the amount of air bypassing the throttle 
body. The ECU performs low and high circuit checks when it is activating the component.
For '06 M.Y. onwards, the electronically controlled throttle needs no IAC, as the ECU commands the throttle 
valve itself to control idle speed.
Component connections (prior to '06 M.Y.)
Connector Description ECU Pin ECU Connector
1 Idle air control value 35 52 Way
2 Battery Voltage - -
3 Ground - -
Malfunction Criteria
P0506 – This code is set if the engine fails to achieve the desired idle speed by more than 100 rpm.
P0507 – This code is set if the engine fails to achieve the desired idle speed by more than 200 rpm.
P0508 – This is set when the ECU does not get the expected feedback (prior to '06 M.Y.).
P0509 – This is set when the ECU does not get the expected feedback (prior to '06 M.Y.).
Enable Criteria:
•	 Engine at idle speed
•	 Battery Voltage between 10 – 16 V
•	 Idle speed learn limit ± 15%
•	 Timer expired 5 seconds
Monitor: Continuous
Potential failure modes:
•	 Throttle body sticking (not fully closing) (prior to '06 M.Y.)
•	 Connector / wiring corroded or loose connections (prior to '06 M.Y.)
•	 Throttle linkage / cable binding (prior to '06 M.Y.)
•	 Induction system air leak
•	 Excessive engine load from front end accessory drive system, e.g. water pump seizing
Notes:
The MIL will be illuminated if the fault is present for 2 consecutive trips.
 
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