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Having an issue with an '05 subaru outback 2.5 NA/sohc. To start out, a brief history: vehicle is slated to have HG's replaced by dealer and was taken there to verify repair a couple days ago. After dealer inspection vehicle was returned to owner who subsequently noticed idle lower than normal and informed the SM via phone about the change in drive-ability. SM insisted all they did was put vehicle on lift to check for HG breach, nothing more. Today owner and I went to Auto zone and had them run their diagnostic scan. Coincidentally, check engine light illuminated right as we parked at autozone. Scan tool retrieved code PO506 or "idle control system RPM lower than expected". WELL DUH... Possible causes include: large vacuum leak, fuel system concern, dirty throttle body, or faulty IAC valve.
Disregarding the possibility that the dealer may be at fault here and this happens to be just a mere coincidence, I would like to know if anyone has had this issue and if there is a common culprit here. I read somewhere that this year utilized a drive-by-wire system and there is no IAC valve :confused:. Gonna wait for the repair to see if anything changes than I'll go through the possible causes but until than I would appreciate any information if you think it may help my cause. Thanks!
 

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2001 VDC/SC One of a Kind
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14,755 Posts
Clean the throttle body of the carbon buildup with a throttle body cleaner and really soft bristle tooth brush and see if that changes it. Usually works.
 

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Discussion Starter #3
Clean the throttle body of the carbon buildup with a throttle body cleaner and really soft bristle tooth brush and see if that changes it. Usually works.
Upon replacement of HG's dealer recognized problem and cleared code with scan tool. Wondering why when I disconnected battery for a short while I couldn't achieve the same results... Can anyone tell me why? I suspect this will happen again so I plan on cleaning the TB per cardoc's recommendation.
Thanks!!
 

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Premium Member
2001 VDC/SC One of a Kind
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14,755 Posts
There is a good possibility that while in the service bay and taken apart they may have cleaned it before reinstallation to remove any possible "glitch" with testing after the repair.

It came back on after you disconnected the battery because the problem was still there. A TB with carbon build up caused by the PCV system feeding oil particulate into the intake air stream, will cause an intermittent issue with idle and throttle response.

To verify whether its been cleaned or not, just remove the air filter assembly and look at it. The TB is something that should be cleaned regularly. An annual cleaning is sufficient.
 
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