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2005 Forester 2.0X AWP
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66 Posts
Discussion Starter #1 (Edited)
Passed the MOT today with emissions:
Fast Idle CO 0.013
HC 70
Lambda 0.997
Natural Idle CO .012

I'm happy it passed but still poor fuel economy. Will the emissions test tell whether the A/F sensor is "lazy"? I had a new original sensor on hand and informed the MOT center/garage to fit it if it failed on emissions. But it passed and they said there was no reason to replace the existing one.
I still average 22mpg combined with a very light right foot... use a scangauge,tyres at 36psi,new plugs, oil, air filter, and the car isn't even a turbo! 34000miles on the clock.

Will fitting a new O2 sensor make a difference? Any thoughts appreciated.
 

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99 UK S-turbo
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8,566 Posts
2.0X is a wideband front sensor, they either work or don't, that is not your issue.

The Lambda1 point is actually defined by the rear sensor, that is right or you'd fail emissions, besides a 1-2% change in fuelling isn't going to change fuel economy by more than 1%!

Simon
 

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Premium Member
98 JDM Stb Manual
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3,787 Posts
They either work or they dont, and dependant on the age of vehicle they fail within range and so therfore you dont get a CEL

so all you notice is that you have your own private space on the petrol station forecourt
 

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05 XT2.5
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1,995 Posts
I'd be very cross at 22mpg and for a not turbo that's outrageous. Can't be right.

You don't fill it with sacks of concrete or something do you?
 

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99 UK S-turbo
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8,566 Posts
They either work or they dont, and dependant on the age of vehicle they fail within range and so therfore you dont get a CEL

so all you notice is that you have your own private space on the petrol station forecourt
Nich, you are confusing your older single sensor car with the later twin sensor car, its more than just having a second sensor you know, the lambda1 point is set by the SECOND sensor which being located downstream of the cat's doesn't age noticeably.

Being OBD if the fueling was the 20% out you get with a failing sensor on a single sensor car, then OBD MIL would be set.

Simon
 

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Premium Member
98 JDM Stb Manual
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3,787 Posts
thats why I said depending on vehicle ie age
 

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2005 Forester 2.0X AWP
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66 Posts
Discussion Starter #7
Thanks for the replies, nope, no bricks or concrete blocks stashed, the cargo space is pretty bare :)
 
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