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2001 Outback 2.5L H4 PFI SOHC AWD Wagon
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Discussion Starter #1
My 01 Outback is running rough narrowing it down and found that my Idle Air Control Valve is dirty, any sure fire ways of cleaning it? I am getting a P0172 code bank 1 Fuel trim malfunction too rich. I already changed the plugs, wires, fuel filter and air cleaner.

Thanks
Kevin
 

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2013 & 2014 Outback
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272 Posts
I have no experience with Subaru Idle control valve but on my old Volvo I was told to spray the little gate valve with carb cleaner and use a Q tip. Clean as well as you can until the little gate valve moves easily. Then take a drop or two of Automatic Transmission fluid and lube between the housing and the OD of the gate valve. It worked very well on my old volvo.
 

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2003 OB 2.5L AT
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66 Posts
on a 2003 OB, the IACV is on the driver side of the Throttle body. There are 2 screws holding it. There is also an electrical connector to it. Make sure car ignition is off.
You can do a youtube search of how to clean the IACV on subarus or you can look up an online parts store to get an idea where it is.

You will need a short #2 philips screw driver, preferably magnetic or new tip, rags and MAF cleaner. Loosen the 2 philipps screws holding it, put a rag underneat it to catch the screws if you drop it. You do not need to remove the electrical connector.
Remove the screws and pull out the IACV slowly and note the gasket.

Put a rag under the IACV valve to catch the cleaner liquid. Spray with MAF cleaner until the carbon build up is gone. Spray any area that you can get to. It should be bright metal on the body and black on the top hat. Let it air dry or you can blow with compressed air. Do not use the freon type air can normally used for computers.
When it is dry, wipe gently the part that goes inside the throttle body to remove residue. Also clean inside the hole where IACV valve inserts to. Use lint free Q-Tips preferably.

You should consider cleaning the throttle body all together instead of just the IACV. It is out, you have access to the small port holes inside where the IACV plugs into. It is also a perfect time to remove the air filter box, clean inside, check or replace the Air filter if it is dirty. This way, you know the Air Intake up to the throttle body is clean.
 

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2001 VDC/SC One of a Kind
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On the 172, is your PCV valve clean? A restricted or plugged PCV can cause a rich code. Then you have exhaust leak, fault in the AF sensor or knock sensor.
 

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My 01 Outback is running rough narrowing it down and found that my Idle Air Control Valve is dirty, any sure fire ways of cleaning it? I am getting a P0172 code bank 1 Fuel trim malfunction too rich. I already changed the plugs, wires, fuel filter and air cleaner.

Thanks
Kevin
RE: my 98 Outback with 235,000 miles
I got an error codes up on the IAC but the car was running fine. I removed it and took it apart -- no small matter for me. Removing the Solenoid positioner on top of the valve body, I could twist the rotating valve assembly back and forth while spraying it with Carb Cleaner. I got a little carbon out, but not much. Putting it all back, I set the Solenoid with the slotted screw openings exactly where they had been, rotationally. On starting it up, I had 4 codes up now instead of one:
P0122 Throttle Pedal Position Sensor/Switch A Circuit Low (the original code)
(Generic SAE Codes) Fuel & Air Metering
P1441 Fuel Tank Pressure Control System High Input
(Subaru) Vehicle Speed Controls & Idle Controls
P1587 Idle Control System Malfunction (Failsafe)
(Subaru) Computer Output Circuits
P1700 Throttle Position Sensor Circuit Malfunction
(Subaru)
P Powertrain
PO-Generic SAE Codes
P1/2 Manufacturer Specific (Subaru)
The RPMS were now running 1600 (specified 1000 for Auto Trans with A/C)
Okay, so I went to the positioner on the IAC and loosened the screws to allow turning the solenoid assembly down, lowering the RPMs to 1000 specified. That's where I'm at now. So yes, I think you can clean the IAC valve easily enough, but you will have to recalibrate the RPMs afterwards. While all this was tricky enough for me, I found that many of the on-line YouTube videos, though helpful to the work, were not complete, or misrepresented what you would have to do overall. My car had clean IAC I concluded. It had only drifted out of spec, so I went to a lot of extra work.

Good luck hope this helps (6 year later) someone else.
 
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