General Mot fail - lambda emissions - resolved

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General Mot fail - lambda emissions - resolved

RichBex

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Apr 5, 2017
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Hi, first post is good news.

Had a recent Mot fail on my daughter's GP, lambda emissions were high. There was also an 'advisory' exhaust leak.

After searching this site I decided to start with the low cost fixes; clean lambda sensors, run through an injector cleaner, etc, before the costly replacing cat and sensors.

While extracting the lambda sensors and removing the manifold heat shield (6 bolts) I could see soot around the joint between the cat and mid-exhaust section ...the post-cat lambda sensor very near to this joint was caked too.

So cleaned both sensors overnight in vinegar and soft toothbrush, then plugged the leak with exhaust paste. After a short blast on the local A-road it passed the re-test, emissions well within limits.

I imagine this would have been fixed with a new cat, as long as it was bolted up tightly, and I'd never have known the difference. But this was my cheapest retest in years and I owe it to contributors here.

Hopefully, this can help others.

All the best and happy MOT-ing.
Rich :D
 
Glad you got it sorted. Yes, high lambda means "weak mixture", low means "rich mixture". If lambda is ever high, exhaust leaks are top of the list of suspects.
 
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