MoT query - not classic

Jan 14, 2004 6 Replies

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DocDelete 22 years ago

Here's another MoT test query for those in the know, before I query with the garage...

The wife's '99 Clio 1.4 failed today due to

"Rear silencer blowing" - OK "Emissions above limits due to rear silencer (lambda sensor)" - ????

The lambda sensors (I think there are two) are ahead and behind the cat on this car, measuring O levels downstream of the engine. The rear box is downstream of this - how can a blowing rear silencer alter the emissions reading, especially "higher". When my wife (she's a canny sod) asked the mechanic for the emissions test printout he said there wasn't one "'cos it had failed".

I'm guessing he didn't even do the emissions incorrectly (perhaps?) assuming all was lost due to the rear silencer.

Gentlefolk, your opinions are valued...

-- Ken Davidson

snipped-for-privacy@removehotmail.com remove remove to email

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MrCheerful 22 years ago

The lack of backpressure will confuse the system.

MrCheerful

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Duncan Wood 22 years ago

Well if it's blowing then the air that gets sucked in the exhaust will confuse the lambda sensor on his emissions tester. Still new exhuast box is easy & only £25+Vat

formatting link

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John Greystrong 22 years ago

The MOT as well as measuring CO also measures O. Any leaks in the exhaust system will suck extra O in pushing the limit over. A lot of people have changed Lamdda sensors when they've just got dodgy joints in their exhaust.

John

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R L Driver 22 years ago

the exhaust what comes out of the tailpipe will not be the same as comes out of the engine ...... the MOT testers machine doesnt know this and if the reading is out side the prescribed limits , you fail . steve the grease

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DocDelete 22 years ago

Thanks again all - I can see also see why a lack of exhaust pressure from the proper hole (tailpipe) due to a large blow can fail to pump the probe too. I guess my main quibble was the lack of emissions test print out - maybe I'm too suspicious / cynical for my own good.

Anyway, it'll be sorted - and thanks to Duncan Wood for the link to BuyPartsBy.

-- Ken Davidson DocDelete

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David Cawkwell 22 years ago

Wow didn't know about the parts website at the bottom. Got some great prices on exhaust system parts.

Cheers.

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