2G P0505 CEL

[ChubMonsta]

I got a CEL for P0505. I replaced IAC Motor with a tested good one and it is still running bad. When sitting at an idle, It slowly fluctuates up to about 2500 rpm then suddenly drops back down to ~1000 rpm. There are no other lights, the connector going into IAC tested good. I am about to test the ECU but im wondering if anyone has ran into this before?

No other CEL
Light fluctuation in RPM (Mainly when warmed but occasionally on cold start)
Performed leak test

 

[Justin DuBois]

I got a CEL for P0505. I replaced IAC Motor with a tested good one and it is still running bad. When sitting at an idle, It slowly fluctuates up to about 2500 rpm then suddenly drops back down to ~1000 rpm. There are no other lights, the connector going into IAC tested good. I am about to test the ECU but im wondering if anyone has ran into this before?

No other CEL
Light fluctuation in RPM (Mainly when warmed but occasionally on cold start)
Performed leak test

Do you have a working FIAV?

This sounds like idle surge - which is a condition where there is too much air bypassing the throttle plate while the throttle plate is closed (closed position switch active) - the ecu cuts ignition over 2500rpm.

If there is an air pocket in the cooling system, the FIAV won't wam up and close down properly. The FIAV might also be broken.

 

[jed344]

I agree this sound's like idle surge and the ecu is cutting timing to not let it rev above 2500rpm.
Generally this is from a boost leak at throttle body or intake manifold ect.
I have also seen FIAV cause this due to it staying open as car warms up so it continues to bypass to much air.
When the FIAV either has no coolant to it or air in it this will cause it to always stay open fully.

 

[ChubMonsta]

I agree this sound's like idle surge and the ecu is cutting timing to not let it rev above 2500rpm.
Generally this is from a boost leak at throttle body or intake manifold ect.
I have also seen FIAV cause this due to it staying open as car warms up so it continues to bypass to much air.
When the FIAV either has no coolant to it or air in it this will cause it to always stay open fully.

I believe Ive had a bypass plate installed. Ill double check to be sure i suppose