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2009 Forester 2.0 XS
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403 Posts
Discussion Starter · #1 ·
Hello,
reading the workshop manual, it states "Excessive back pressure in exhaust system" as a possible cause for overheating. Does this depend on a malfunction of the exhaust system, or can it happen as an one-off incident? Can cat converters be affected by higher than normal EGT and somewhat cause an additional restriction to the exhaust gases?

I am chasing down an overheating situation with my car which seems to only happen every 2 years or more, and always on the highway.

Thanks!
 
2017 2.5i Fozy CVT
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1,283 Posts
If a cat goes bad, a couple things can happen; the" honecomb" (catalyst itself)material inside can glaze over with deposits which can restrict, and it may also break apart into chunks that can slow exhaust flow,as well.

The main symptom is a lack of response to the accelerator. It almost seems as if the more you step on it the slower you go.
 

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2009 Forester 2.0 XS
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403 Posts
Discussion Starter · #3 ·
Thanx but I guess this does not work on an one-off basis, I mean either the catalyst is good or bad, no?
 
2017 2.5i Fozy CVT
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1,283 Posts
True, but,,, Hard to say, not knowing how down on power it is compared to new.

If you( briefly ) remove the Oxygen sensor before the cat and get a noticeable increase in power, that is a big clue of restriction in the cat.

The sensor is considered a maintenance item and should be replaced, some say, every 100000 mi/160000 k.

OEM is best, as cheaper aftermarket potentially results in sensors with a slower response time.
 

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2009 Forester 2.0 XS
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403 Posts
Discussion Starter · #5 ·
Thnx! I got almost 170,000 Km So I replace the O2 sensot (aka -lambda, right?) , what about the catalyst itself ?
 
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