P0420, fan running, metal cracklin, bad idle - Subaru Outback - Subaru Outback Forums
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post #1 of 5 (permalink) Old 09-06-2013, 08:07 PM Thread Starter
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P0420, fan running, metal cracklin, bad idle

Im trying to diagnose CEL. Reset codes and the first code to appear was P0420.

Not sure if related but figured I would mention:

Ive noticed that my fan has been turning on, blower off, but the engine temperature was just fine. It is actually sort of cool out and I've rarely ever heard the fan run.

Also, you know the sound you get after you turn the car off sometimes, the exhaust and metal cooling down? Well it makes that noise all the time now, even when car is running. I may be crazy but it all seems new.

Also the car is drivable, but you can tell its hurting a little, idles very bad while in Drive at a stop. Throttle, idle is just not happy all around.

So obvious sings are o2 or cat?

I'm pretty sure right before I got the car @ 80k, there were records of Subaru, under warranty replacing the front two down exhaust down pipes and o2 sensors? maybe just one sensor, but could have been both.

Do any of these symptoms point directly to one or the other? Try o2 first?

2004 H4 160k

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post #2 of 5 (permalink) Old 09-06-2013, 08:56 PM
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Some reading before throwing parts at it:

P0420 Diagnosis

An Engineers Perspective on the P0420 Catalytic Efficiency code

my fan has been turning on, blower off
Which fan, blower, is this referring to?

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post #3 of 5 (permalink) Old 09-06-2013, 10:34 PM
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Very confused. I have MAF and MAP? Error codes

And I believe the P1090 posted in the above thread is actually a P0109 - MAP sensor

Battery, grounds or vacuum leak. Could be a combination of them, maybe more.

Vaccum leak would cause the MAP and MAF codes; would also cause a 420. We know what poor conductance does to a car.

Start hunting.
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post #4 of 5 (permalink) Old 09-06-2013, 11:32 PM
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is the car an auto? Try shifting to neutral at a stop and see if idle/vibration seems better. Could be axles shaking.

The other sound could be heat shields.

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post #5 of 5 (permalink) Old 09-07-2013, 09:07 AM
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I've noticed on speed density motors that vac leaks will make them idle higher. If it idles too low, first thing I'd check would be the IAC valve. They're known for getting gunked up.

Worth pulling off and cleaning it out. Gasket is usually re-usable.

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I seem to get a lot of "will xx fit in my car?" emails. . . I'm not the authority on everything Subaru, so I very well may tell you the wrong answer as there's nobody else to check me. Please search or ask via the forums first. . .when I answer you via email, it never gets posted and nobody else can confirm or refute my answer.
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