Author Topic: MOT fail, emissions lambda reading?  (Read 3391 times)

Offline Dan_GTi8v

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MOT fail, emissions lambda reading?
« on: 10 October 2011, 11:07 »
What can I do to fix the above MOT fail? on both fast idles I got a reading of 1.08, limit is 1.03. Would this just be as simple as fitting a new lambda sensor?

Its an AUM 1.8t in a mk3 so only has the pre cat lambda. If its the pre car reading would this mean it couldn't be down to the cat? This is what I was worried about as it has a sports cat fitted

cheers

edit: Could it also be anything to do with the maf? I've had some indications that thats knackered as well (even though it was new from vw 6 months ago)
« Last Edit: 10 October 2011, 11:11 by Dan_GTi8v »
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Offline Dan_GTi8v

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Re: MOT fail, emissions lambda reading?
« Reply #1 on: 10 October 2011, 12:42 »
after some research I'm thinking it may even be something as simple as an air leak in the exhaust. Other readings are all fine just the lambda that's high

Think I'm gonna clean the maf then take it to a recommended garage to check the exhaust and do an emissions test, and give it a good blast before taking it back for a retest
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Offline topher

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Re: MOT fail, emissions lambda reading?
« Reply #2 on: 10 October 2011, 13:36 »
you can check that yourself with vcds in engine mvb 31. Also check what your fuel trims are at (block 32). Could be maf related, the conversions we do we end up fixing an extra bracket to the maf housing as we found the vibrations were killing them every few months.

Offline Dan_GTi8v

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Re: MOT fail, emissions lambda reading?
« Reply #3 on: 10 October 2011, 14:29 »
I don't have vagcom :( The garage I was recommended to see has it which is why he told me to go there, but it seems he's not in his workshop no one on the estate has seen him around :(

Interesting about the extra bracket though, what kind of bracket is it, just something fixed to stop it moving? My induction kit came with a bracket that I never fitted as it was made for the mk4, but I'm sure I could bodge it to fit

I could hear a small ticking noise coming from one of the joins after the cat so could also be this (I've been told). I'll try and get this sorted tomorrow then take it for a drive with the maf unplugged see if anything feels different
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Offline Dan_GTi8v

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Re: MOT fail, emissions lambda reading?
« Reply #4 on: 11 October 2011, 09:16 »
I'm learning a lot about emissions recently  :grin:

got it booked in today to get the exhaust checked over and also fix my brake pipe that needs doing, then I'm gonna give this passat maf a go, if I get no joy with that its down to ecp for a new bosch one (and fit a bracket to stop vibrations), then off to the autofactors to get some of this lower emission additive I've been reading about, then book the resest and pray!

cheers all for the help over the various threads I've had since yesterday :afro:
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Offline Dan_GTi8v

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Re: MOT fail, emissions lambda reading?
« Reply #5 on: 11 October 2011, 17:44 »
On the check over at the garage today the guy found that my lambda wiring was f**ked, it had somehow got in the way of the driveshafts and the black wire has been worn away, and it just happens that the black wire is the sender wire for the sensor.
 He reckons after replacing it it should now pass the emissions, but I'm a bit sceptical as things on my car are never that simple  :grin: What you reckon could this be whats giving me a high lambda reading?
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