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2005 Subaru Forester Catalytic Converter/Oxygen Sensor Prob

Tiny
KATHY MAGEE
  • MEMBER
  • 2005 SUBARU FORESTER
  • 4 CYL
  • AWD
  • MANUAL
  • 86,224 MILES
Since 2005 I have had continuing problems with check engine light. Code PO 420 is the consistant computer code. I have been taking the car to the dealer. My catalytic converter has been replaced four times so far. My oxygen sensors have been replaced twice.

Most of the time when this problem occurs the weather is around 40 degrees and it is humid. Then my car stalls out, bucks and won't accelerate. But sometimes the check engine light comes on without any noticeable poor performance. I think the symptom is being treated, but not the cause. What could be the cause?
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Thursday, March 26th, 2009 AT 11:41 AM

2 Replies

Tiny
BLACKOP555
  • MECHANIC
  • 10,371 POSTS
Has the bank one sensor one and sensor 2 o2 sensors replaced? They use eachother for refrence.

There may also be a exhaust leak in the system causing that to show up.

Are the convertors actually failing or is the code just showing up?
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Thursday, March 26th, 2009 AT 2:22 PM
Tiny
BLACKOP555
  • MECHANIC
  • 10,371 POSTS
Make sure you are using unleaded gas. And if you are using fuel additives make sure they are convertor safe.

The ignition timing may be off or even a bad intake temp sensor and coolant temp sensor can be causing this.
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Thursday, March 26th, 2009 AT 2:23 PM

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